Structural characterization of developmentally expressed antigenic markers on chicken erythrocytes using monoclonal antibodies

Developmental distribution of reelin-positive cells and their secreted product in the rodent spinal cord

To date, only sympathetic and parasympathetic preganglionic neurons are known to migrate abnormally in reeler mutant spinal cord. Reelin, the large extracellular matrix protein absent in reeler, is found in wild-type neurons bordering both groups of preganglionic neurons. To understand better Reelin's function in the spinal cord, we studied its developmental expression in both mice and rats. A remarkable conservation was found in the spatiotemporal pattern of Reelin in both species. Numerous Reelin-expressing cells were found in the intermediate zone, except for regions containing somatic and autonomic motor neurons. A band of Reelin-positive cells filled the superficial dorsal horn, whereas only a few immunoreactive cells populated the deep dorsal horn and dorsal commissure. High levels of diffuse Reelin product were detected in the lateral marginal and ventral ventricular zones in both rodent species. This expression pattern was detected at all segmental spinal cord levels during embryonic development and remained detectable at lower levels throughout the first postnatal month. To discriminate between the cellular and secreted forms of Reelin, brefeldin A was used to block secretion in organotypic cultures. Such perturbations revealed that the high levels of secreted Reelin in the lateral marginal zone were derived from varicose axons of more medially located Reelin-positive cells. Thus, the laterally located secreted Reelin product may normally prevent the preganglionic neurons from migrating too far medially. Based on the strong evolutionary conservation of Reelin expression and its postnatal detection, Reelin may have other important functions in addition to its role in neuronal migration.

The superior olivary complex of the hamster has multiple periods of cholinergic neuron development

Cholinergic neurons of the superior olivary complex share a common embryological and phylogenetic origin with brainstem motor neurons and serve as the major descending efferent pathway either to the cochlea as part of the olivocochlear system or to the cochlear nucleus. In this study, we investigated the developmental expression patterns of choline acetyltransferase (ChAT) and its co-localization with calcitonin gene-related peptide within the superior olivary complex and neighboring brainstem motor nuclei. At embryonic day 12, neurons in the ventral nucleus of the trapezoid body were first to express ChAT. The temporal expression pattern of both ChAT mRNA and immunoreactivity in this periolivary region mimicked motor neurons in the facial and trigeminal motor nuclei. Just before birth, shell neurons surrounding the lateral superior olive expressed ChAT. Neither ChAT-positive periolivary neurons nor shell neurons co-expressed calcitonin gene-related peptide during development or in the adult. Immediately following birth, intrinsic neurons within the lateral superior olive expressed ChAT but not calcitonin gene-related peptide. However, a transient increase in the number of ChAT-positive neurons in the lateral superior olive coincided with the onset of the calcitonin gene-related peptide co-expression within these neurons. We conclude that ChAT expression appears first in periolivary regions containing medial olivocochlear neurons, precedes the expression of calcitonin gene-related peptide in the superior olivary complex, and is co-expressed with calcitonin gene-related peptide within the lateral superior olive containing lateral olivocochlear neurons. These data suggest that the lateral olivocochlear system co-expresses ChAT and calcitonin gene-related peptide, whereas the medial olivocochlear system does not.

Evidence for a cell-specific action of Reelin in the spinal cord

Reelin, the extracellular matrix protein missing in reeler mice, plays an important role in neuronal migration in the central nervous system. We examined the migratory pathways of phenotypically identified spinal cord neurons to determine whether their positions were altered in reeler mutants. Interneurons and projection neurons containing choline acetyltransferase and/or NADPH diaphorase were studied in E12.5-E17.5 reeler and wild-type embryos, and their final locations were assessed postnatally. While three groups of dorsal horn interneurons migrated and differentiated normally in reeler mice, the migrations of both sympathetic (SPNs) and parasympathetic preganglionic neurons (PPNs) were aberrant in the mutants. Initially reeler and wild-type SPNs were detected laterally near somatic motor neurons, but by E13.5, many reeler SPNs had mismigrated medially. Postnatally, 79% of wild-type SPNs were found laterally, whereas in reeler, 92% of these neurons were positioned medially. At E13.5, both reeler and wild-type PPNs were found laterally, but by E14.5, reeler PPNs were scattered across the intermediate spinal cord while wild-type neurons correctly maintained their lateral location. By postnatal day 16, 97% of PPNs were positioned laterally in wild-type mice; in contrast, only 62% of PPNs were found laterally in mutant mice. In E12.5-E14.5 wild-type mice, Reelin-secreting cells were localized along the dorsal and medial borders of both groups of preganglionic neurons, but did not form a solid barrier. In contrast, Dab1, the intracellular adaptor protein thought to function in Reelin signaling, was expressed in cells having positions consistent with their identification as SPNs and PPNs. In combination, these findings suggest that, in the absence of Reelin, both groups of autonomic motor neurons migrate medially past their normal locations, while somatic motor neurons and cholinergic interneurons in thoracic and sacral segments are positioned normally. These results suggest that Reelin acts in a cell-specific manner on the migration of cholinergic spinal cord neurons.

Selective expression of major histocompatibility complex (MHC) antigens and modulation of T-cell differentiation in chickens with increased MHC-chromosome dosages

Increased dosage of genes belonging to the immunoglobulin superfamily may be responsible for some of the less noticeable but targeted phenotypic disturbances seen in trisomy conditions of humans and animals. We used an avian aneuploidy model to study the specific effects of extra major histocompatibility complex (MHC)-microchromosome dosage on the progression of thymocyte differentiation through a broad period of embryonic and neonatal development. The particular goal in the present investigation was to determine whether a reduction in the number of thymocytes, previously observed in the developing thymus of MHC aneuploids, is accompanied by particular alterations in thymocyte differentiation. We hypothesized that the subpopulation structure and/or developmental pattern for thymocyte differentiation are characteristically perturbed (delayed or modified) by increased MHC-chromosome dosage in cells. The regulation of MHC surface antigen expression in aneuploid thymocytes was also studied to detect dosage-dependent expression for one and possibly more sub-regions (class I, II, IV) of the avian MHC. Surface densities of MHC class I antigens on thymocytes were increased significantly at all ages studied, for example by 15% and 45% in trisomics and tetrasomics, respectively at 22 days post-hatching. The surface density of CT1 antigen, a thymocyte-specific marker, was also increased in a dosage-dependent manner, but only in juveniles. Increases in the proportion of alpha beta 1, TCR+ and CD3+ thymocytes were observed in juveniles, with no alterations in other TCR-expressing thymocytes. No major alterations in CD4 and CD8 thymocyte populations were observed. These results demonstrate a targeted effect of extra MHC-chromosome dosage towards enhanced class I and CT1, and not class II or IV, expression. The increased MHC-microchromosome dosage appears to influence primarily immature thymocytes expressing alpha beta 1 TCR and CD3.

Commissural fibers may guide cholinergic neuronal migration in developing rat cervical spinal cord

The present investigation examines the role of intercellular relationships in the guidance of neuronal migration in embryonic rat cervical spinal cord. A "U-shaped" group of cholinergic neurons, was first detected on embryonic days (E) 15.5-16 surrounding the ventral proliferative zone. At these stages, no cholinergic cells were observed in the dorsal spinal cord, but by E17, many of the "U-shaped" group of cholinergic cells appeared to have translocated dorsally, to become the cholinergic dorsal horn cells seen in older animals. Between E16 and E17, these choline acetyltransferase (ChAT)-immunoreactive cells displayed primitive processes oriented dorsoventrally, suggesting migration along that axis. Two early forming substrates present in embryonic spinal cord have been implicated in the guidance of other populations of migrating neurons: glial cells organized in radial arrays and commissural axons aligned along the dorsoventral axis. Involvement of the commissural fibers with cholinergic cell migration seems more likely because the fibers and the translocation pathway have similar orientations. In double-labeling immunocytochemical studies of E15.5-17 spinal cord, some immature ChAT-containing neurons were directly adjacent to commissural fibers, as identified by SNAP/TAG-1 immunoreactivity. The temporal and spatial coincidence of developing cholinergic neurons and commissural axons is consistent with the hypothesis that these neurons could use commissural fibers as migratory guides. In addition, conventional electron micrographs were examined to determine if immature neuronal profiles were physically apposed to commissural axons. Immature neurons with leading and trailing processes oriented dorsally and ventrally, respectively, were embedded within and aligned along bundles of commissural fibers or along other similarly oriented neurons. This direct apposition of immature cells to the surfaces of commissural axons and other bipolar neurons is consistent with the hypothesis that the "U-shaped" group of cholinergic neurons may use commissural axons and other cohort neurons for guidance during their dorsal migration.

Transient and continuous expression of NADPH diaphorase in different neuronal populations of developing rat spinal cord

Nitric oxide is a novel intercellular messenger whose role in neuronal development is not yet known. As a first step toward elucidating its developmental function, we examined the pattern of NADPH diaphorase histochemical staining, an indicator of the presence of nitric oxide synthase, in the rat spinal cord at pre and postnatal ages. Some types of neurons expressed diaphorase activity transiently during development. For example, a subset of somatic motor neurons, located in the ventrolateral corner of a few caudal segments of the cervical spinal cord, were diaphorase-positive beginning on E15, but gradually became diaphorase-negative by birth. In contrast, other spinal neurons expressed diaphorase activity continuously from development into adulthood. Preganglionic autonomic motor neurons became diaphorase-positive early in their development, as they were migrating toward their adult positions. Other spinal neurons, such as those in superficial dorsal horn, first expressed diaphorase relatively late in their development, after reaching their final location. The transient expression in some cell types, as well as the early expression in others, suggest that nitric oxide may have an important role(s) during development, which may differ from its functions in the adult nervous system.

Choline acetyltransferase and NADPH diaphorase are co-expressed in rat spinal cord neurons

Phenotypic diversity underlies the complex functioning of the nervous system. One characteristic in which neurons differ from one another is the kind of molecules that they use for intercellular signalling. The classical neurotransmitter acetylcholine, synthesized by the enzyme choline acetyltransferase, is used by five groups of neurons in the rat spinal cord. Another messenger is nitric oxide, which is synthesized by nitric oxide synthase. Neurons that express nitric oxide synthase can be stained specifically by NADPH diaphorase histochemistry. In the spinal cord, approximately five groups of neurons are labeled by the diaphorase reaction, and some of these populations overlap with cholinergic groups. To determine the proportions of neurons that co-express choline acetyltransferase and nitric oxide synthase, we performed choline acetyltransferase immunocytochemistry and diaphorase histochemistry on single sections of rat spinal cord. Some cell types were single-labeled: somatic motor neurons were choline acetyltransferase-immunoreactive only, and neurons in lamina II were diaphorase-positive only. Four cell groups included double-labeled cells. Autonomic motor neurons were either double-labeled (62%) or choline acetyltransferase-only (37%), partition cells in lamina VII were double-labeled (54%) or choline acetyltransferase-only (45%), neurons in laminae III-V of the dorsal horn were double-labeled (70%) or diaphorase-only (27%), and neurons surrounding the central canal were double-labeled (56%), choline acetyltransferase-only (23%) or diaphorase-only (21%). These data indicate that certain spinal cord populations may be heterogeneous with regard to the intercellular messenger phenotypes involving acetylcholine and nitric oxide.(ABSTRACT TRUNCATED AT 250 WORDS)

Embryonic development of rat sympathetic preganglionic neurons: possible migratory substrates

Spinal somatic and autonomic (sympathetic preganglionic) motor neurons are generated synchronously and, subsequently, migrate from the ventricular zone together to form a common primitive motor column. However, these two subsets of motor neurons ultimately express several phenotypic differences, including somal size, peripheral targets, and spinal cord locations. While somatic motor neurons remain ventrally, autonomic motor neurons (AMNs) move both dorsally and medially between embryonic days 14 and 18, when they approximate their final locations in spinal cord. The goal of the present investigation was to determine the potential guidance substrates available to AMNs during these movements. The dorsal translocation was studied in developing upper thoracic spinal cord, because, at this level, the majority of AMNs are located dorsolaterally. Sections were double-labeled by ChAT (choline acetyltransferase) and SNAP/TAG-1 (stage-specific neurite associated protein/transiently expressed axonal surface glycoprotein) immunocytochemistry to visualize motor neurons and the axons of early forming circumferential interneurons, respectively. Results showed that during the developmental stage when AMNs translocated dorsally, SNAP/TAG-1 immunoreactive lateral circumferential axons were physically located along the borders of the AMN region, as well as among its constituent cells. These findings indicate that lateral circumferential axons, as well as the SNAP/TAG-1 molecules contained upon their surfaces, are in the correct spatial and temporal position to serve as guidance substrates for AMNs. The medial translocation was studied in developing lower thoracic-upper lumbar spinal cord, because, at this level, more than half of the AMNs are medially located. Sections were double-labeled by ChAT and vimentin immunocytochemistry to visualize motor neurons and radial glial fibers, respectively. Observations on consecutive developmental days of the medial translocation revealed that AMNs were aligned with parallel arrays of radial glial fibers. Thus, the glial processes could serve as guides for the AMN medial movement. Future experimental analyses will examine whether circumferential axons and radial glial fibers are in fact functioning as migratory guides during AMN development, and, if so, whether specific surface molecules on these guides trigger the subsequent differentiation of AMNs.

Association interneurons of embryonic rat spinal cord transiently express the cell surface glycoprotein SNAP/TAG-1

SNAP/TAG-1 is a 135 kDa glycoprotein of the immunoglobulin superfamily that is transiently expressed upon the surfaces of developing axons. In the embryonic rodent spinal cord, this molecule is expressed by motor neurons, dorsal root ganglion cells, and commissural neurons (Yamamoto et al.: J. Neurosci. 6:3576-3594, 1986; Dodd et al.: Neuron 1:105-116, 1988). The commissural cells are a subset of early-forming dorsal horn interneurons whose axons follow a circumferential course in the embryonic spinal cord. The axons of commissural neurons cross the developing ventral commissure to terminate on contralateral synaptic targets, whereas those of the other subset of circumferential cells, the association interneurons, remain on the same side of the spinal cord to form ipsilateral, terminal synaptic fields. The difference between the axonal trajectories of these two subsets of nerve cells raised the question of whether or not association interneurons would also express the SNAP/TAG-1 epitope and, if so, how would this expression be related to that of the commissural cells. Immunocytochemistry for SNAP/TAG-1 and choline acetyltransferase (ChAT) was used to answer these questions. The results indicated that association interneurons expressed SNAP/TAG-1 epitopes and that this expression began later and lasted longer than that of the commissural neurons. Other new findings of this study included the identification of a lateral subgroup of commissural fibers that expressed SNAP/TAG-1 later than their more medially located counterparts, and these lateral fibers were more pronounced in the thoracic spinal cord than at cervical levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Small cholinergic neurons within fields of cholinergic axons characterize olfactory-related regions of rat telencephalon

Small immunoreactive cholinergic neurons were detected in the main and accessory olfactory bulbs of the rat with choline acetyltransferase immunocytochemistry. Such cells were also found in additional forebrain regions that received direct efferent innervation from the main olfactory bulb, such as the anterior olfactory nucleus, two subdivisions of the olfactory amygdala (nucleus of the lateral olfactory tract and anterior cortical nucleus), and the cortical-amygdaloid transition zone. Cholinergic neurons located in these olfactory-related regions were similar to each other morphologically and to those previously described by other investigators in the cerebral cortex, the hippocampus, and the basolateral amygdala. Somal measurements indicated that choline acetyltransferase-positive cells in olfactory-related regions were all essentially the same size, measuring 13-14 by 8-9 microns in major and minor diameters, respectively. In addition, these small cells were commonly bipolar in form with thin, smooth dendrites, and such characteristics have generally been associated with intrinsic, local circuit neurons in the forebrain. Depending on their location, however, these small cholinergic neurons differed from each other with regard to their frequency and dendritic orientation within planar sections. Choline acetyltransferase-immunoreactive cells in most cortical regions were relatively numerous and usually exhibited long, planar dendrites oriented perpendicularly to the pial surface. In contrast, dendrites of cholinergic neurons found in "cortical-like" regions (e.g. olfactory bulbs or nucleus of the lateral olfactory tract) were relatively sparse in number and appeared to be distinctly non-planar and randomly oriented. Despite these differences, the small choline acetyltransferase-positive cells had many features in common, including their distribution within forebrain regions that contained substantial terminal networks of choline acetyltransferase-positive axons thought to be derived primarily from the basal forebrain complex. In the rat, at least, the presence of small cholinergic interneurons within forebrain regions innervated by the large cholinergic projection neurons of the basal forebrain seems to be developing as a general principle of telencephalic organization. However, differences in both the size and the distribution of the terminal fields derived from each source imply a functional diversity between the intrinsic and extrinsic cholinergic systems of the forebrain.

Immunogenetics and the major histocompatibility complex

The poultry immune system is a complex system involving many different cell types and soluble factors that must act in concert to give rise to an effective response to pathogenic challenge. The complexity of the immune system allows the opportunity for genetic regulation at many different levels. Cellular communication in the immune response, the production of soluble factors, and the rate of development of immune competency are all subject to genetic influences. The genes of the major histocompatibility complex (MHC) encode proteins which have a crucial role in the functioning of the immune system. The MHC antigens of chickens are cell surface glycoproteins of three different classes: Class I (B-F), Class II (B-L) and Class IV (B-G). The MHC antigens serve as essential elements in the regulation of cell-cell interactions. The MHC has been shown to influence immune response and resistance to autoimmune, viral, bacterial and parasitic disease in chickens. The MHC has been the primary set of genes identified with genetic control of immune response and disease resistance, but there are many lesser-characterized genes outside of the MHC that also regulate immunoresponsiveness. Polygenic control has been identified in selection experiments that have produced lines of chickens differing in antibody levels or kinetics of antibody production. These lines also differ in immunoresponsiveness and resistance to a variety of diseases. Understanding the genetic bases for differences in immunoresponsiveness allows the opportunity selectively to breed birds which are more resistant to disease. Indirect markers that can be used for this selection can include the MHC genes and immune response traits that have been associated with specific or general resistance to disease.

Generation patterns of immunocytochemically identified cholinergic neurons at autonomic levels of the rat spinal cord

The time at which a neuron is "born" appears to have significant consequences for the cell's subsequent differentiation. As part of a continuing investigation of cholinergic neuronal development, we have combined ChAT immunocytochemistry and [3H]thymidine autoradiography to determine the generation patterns of somatic and autonomic motor neurons at upper thoracic (T1-3), upper lumbar (L1-3), and lumbosacral (L6-S1) levels of the rat spinal cord. Additionally, the generation patterns of two subsets of cholinergic interneurons (partition cells and central canal cluster cells) were compared with those of somatic and autonomic motor neurons. Embryonic day 11 (E11) was the first day of cholinergic neuronal generation at each of the three spinal levels studied, and it also was the peak generation day for somatic and autonomic neurons in the upper thoracic spinal cord. The peak generation of homologous neurons at upper lumbar and lumbosacral spinal levels occurred at E12 and E13, respectively. Somatic and autonomic motor neurons were generated synchronously, and their production at each rostrocaudal level was virtually completed within a 2-day period. Cholinergic interneurons were generated 1 or 2 days later than motor neurons at the same rostrocaudal level. In summary, the birthdays of all spinal cholinergic neurons studied followed the general rostrocaudal spatiotemporal gradient of spinal neurogenesis. In addition, the generation of cholinergic interneurons also followed the general ventrodorsal gradient. In contrast, however, autonomic motor neurons disobeyed the rule of a ventral-to-dorsal progression of spinal neuronal generation, thus adding another example in which autonomic motor neurons display unusual developmental patterns.

Development of rostrocaudal dendritic bundles in rat thoracic spinal cord: analysis of cholinergic sympathetic preganglionic neurons

Using monoclonal antibodies to choline acetyltransferase (ChAT) and glial fibrillary acidic protein (GFAP), we have analyzed the development of the dendritic bundles formed by cholinergic sympathetic preganglionic neurons (SPNs) in relationship to changes in the organization of glial fibers. In adult rat thoracic spinal cord, SPNs in the intermediolateral (IML) and central autonomic (CA) regions extend dendrites in both the mediolateral and rostrocaudal directions, forming a ladder-like pattern in horizontal sections of thoracic spinal cord. We report that, while the mediolateral dendrites form prenatally, the rostrocaudal dendritic bundles are not detected until at least a week later, during early postnatal life. The rostrocaudal dendrites develop rapidly during the first postnatal week, and achieve an adult-like pattern by postnatal day 14. The observed ontogenetic arrangements of dendritic bundles were correlated with the developing organization of astroglial processes with which they are intimately associated. While the appearance of mediolateral dendrites is consistent with the radial organization of glial in the embryonic spinal cord, the developmental time course of the rostrocaudal dendritic bundles coincides with the transformation of glial cells from this predominantly radial or transverse orientation to the randomly-oriented, stellate pattern of mature astrocytes. This temporal association suggests that ontogenetic changes in the organization of glial cells may contribute to the differential development of mediolateral and rostrocaudal dendritic patterns in the spinal cord.

Immunoglobulin variable-region-like domains of diverse sequence within the major histocompatibility complex of the chicken

The highly polymorphic B-G antigens are considered to be part of the major histocompatibility complex (MHC) of the chicken, the B system of histocompatibility, because they are encoded in a family of genes tightly linked with the genes encoding MHC class I and class II antigens. To better understand these unusual MHC antigens, full-length B-G cDNA clones were isolated from B21 embryonic erythroid cell cDNA library, restriction-mapped, and sequenced. Five transcript types were identified. Analysis of the deduced amino acid sequences suggests that the B-G polypeptides are composed of single extracellular domains that resemble immunoglobulin domains of the variable-region (V) type, single membrane-spanning domains typical of integral membrane proteins, and long cytoplasmic tails. Sequence diversity among the five transcript types was found in all domains, notably including the B-G immunoglobulin V-like domains. The cytoplasmic tails of the B-G antigens are made up entirely of units of seven amino acid residues (heptads) that are typical of an alpha-helical coiled-coil conformation. The heptads vary in number and sequence between the different transcripts. The presence within B-G polypeptides of polymorphic immunoglobulin V-like domains warrants further investigations to determine the degree and nature of variability within this domain in these unusual MHC antigens.

Embryonic development of choline acetyltransferase in thoracic spinal motor neurons: somatic and autonomic neurons may be derived from a common cellular group

This investigation focused on the relationship between neurotransmitter phenotype expression and rat motor neuron development, as studied with choline acetyltransferase (ChAT) immunocytochemical techniques. The development of two subclasses of motor neurons, somatic and autonomic efferents, was examined in the upper thoracic spinal cord. ChAT was first detected in a few neurons on embryonic day 12 1/2 (E12 1/2), and in numerous cells located in a single, ventrolaterally located column in the intermediate zone on E13. By E14, this group of ChAT-positive neurons was more intensely immunoreactive, and their axons could be traced to appropriate targets in developing somatic muscle and paravertebral sympathetic ganglia. During the E15-16 period, somatic and autonomic motor neurons separated into two distinct subgroups, with the latter cells being observed to translocate dorsally. By E17, these autonomic motor neurons reached their final positions in the midportion of the intermediate zone. The autonomic motor neurons were observed to extend transverse dendritic bundles across the spinal cord between E15-16, but evidence of the longitudinal bundles of sympathetic preganglionic dendrites was not observed until after birth. A recent study of cholinergic thoracic motor neurons found that both somatic and autonomic cells were generated synchronously during the E11-12 period (Barber et al., Soc Neurosci Abstr 15:588, 1989). In combination with the present results, these data indicate that no more than 1 1/2 days are necessary after motor neuron genesis before a few cells begin to express detectable levels of ChAT, and that no more than 2 days are required before large numbers express this marker of the cholinergic phenotype. Further comparisons of the present findings with those of previous investigations of the development of both somatic and autonomic motor neurons (Dennis et al., Dev Biol 81:266, 1981; Rubin, J Neurosci 5:685, 697, 1985) indicate that these cells contain ChAT at the time their axons are growing toward their respective peripheral targets 1 day before the time when physiological evidence of function is manifest. Furthermore, the present results suggest that both subclasses of motor neurons initially migrate together from the ventricular zone into a single motor column within the ventral intermediate zone, and that the autonomic neurons subsequently translocate dorsally. Thus, autonomic motor neurons appear to be an exception to the generalization that postmitotic neurons migrate directly from the germinal zone to their final positions within the central nervous system.

The "adjuvant effect" of the polymorphic B-G antigens of the chicken major histocompatibility complex analyzed using purified molecules incorporated in liposomes

The polymorphic B-G region of the chicken major histocompatibility complex has previously been shown to mediate an "adjuvant effect" on the humoral response to other erythrocyte alloantigens. We demonstrate here that B-G molecules purified with monoclonal antibodies exert this adjuvant effect on the production of alloantibodies to chicken class I (B-F) molecules, when the two are in the same liposome. The adjuvant effect may in part be mediated by antibodies, since the antibody response to B-G molecules occurs much faster than the response to B-F molecules, and conditions in which antibodies to B-G are present increase the speed of the response to B-F molecules. We also found that the presence of B-G molecules in separate liposomes results in a lack of response to B-F molecules. In the light of this and other data, we consider the possible roles for the polymorphic B-G molecules, particularly for the generation of B cell diversity, in the immune systems of birds and other animals.

Chicken major histocompatibility complex-encoded B-G antigens are found on many cell types that are important for the immune system

B-G antigens are a polymorphic multigene family of cell surface molecules encoded by the chicken major histocompatibility complex (MHC). They have previously been described only on cells of the erythroid lineage. By using flow cytometry, section staining, and immunoprecipitation with monoclonal antibodies and rabbit antisera to B-G molecules and by using Northern blots with B-G cDNA clones, we demonstrate here that B-G molecules and RNA are present in many other cell types: thrombocytes, peripheral B and T lymphocytes, bursal B cells and thymocytes, and stromal cells in the bursa, thymus, and caecal tonsil of the intestine. The reactions also identify at least one polymorphic B-G determinant encoded by the B-F/B-L region of the chicken MHC. The serology and tissue distribution of B-G molecules are as complex as those of mammalian MHC class I and class II molecules. These facts, taken with certain functional data, lead us to suggest that B-G molecules have an important role in the selection of B cells in the chicken bursa.

Generation patterns of immunocytochemically identified cholinergic neurons in rat brainstem

Combined [3H]thymidine autoradiographic and choline acetyltransferase (ChAT)-immunocytochemical techniques were used to answer questions concerning the generation of specific classes and subclasses of cholinergic neurons in rat brainstem. First, the generation of rostrally and caudally located neurons of the same class (i.e. somatic efferent oculomotor and hypoglossal nuclei, respectively) were compared. Results indicated that, although embryonic day 11 (E11) was the peak birthday for both nuclei, hypoglossal neurons were generated significantly earlier than oculomotor neurons, indicating a caudorostral generation gradient for brainstem somatic motor nuclei. Second, the generation patterns of 3 different subclasses of motor neurons at the same brainstem level were compared; namely those of the somatic efferent hypoglossal nucleus (XII), the general visceral efferent dorsal nucleus of the vagus (X), and the predominantly special visceral efferent nucleus ambiguus. All 3 subclasses of cholinergic cells had the same peak day (E11) and overall period of generation (E11-12). However, statistical analyses indicated a precocious generation of nucleus ambiguus, but no developmental differences between N, XII and N. X. It is suggested that nucleus ambiguus is formed earlier than N. XII and N. X, due to its more ventral location within a ventrodorsal neurogenetic gradient. Third, the generation patterns of different classes of large cholinergic neurons were examined. Specifically, the birthdays of cholinergic non-motor projection neurons of the pedunculopontine-laterodorsal tegmental nuclei (PPT-LDT) were contrasted to those of the cholinergic brainstem motor neurons. The peak birthdays of both rostrally and caudally located motor neurons were two days earlier than those of the PPT-LDT neurons. Thus, large cholinergic cells projecting to peripheral targets are born significantly earlier than those projecting within the CNS, even though the former are located more rostrally on the caudorostral neurogenetic gradient. This represents an apparent exception to the emerging rule that cholinergic neurons obey the general gradients of neurogenesis manifest in the regions of the central nervous system where they reside.

The MHC molecules of nonmammalian vertebrates

There is very little known about the long-term evolution of the MHC and MHC-like molecules. This is because both the theory (the evolutionary questions and models) and the practice (the animals systems, functional assays and reagents to identify and characterize these molecules) have been difficult to develop. There is no molecular evidence yet to decide whether vertebrate immune systems (and particularly the MHC molecules) are evolutionarily related to invertebrate allorecognition systems, and the functional evidence can be interpreted either way. Even among the vertebrates, there is great heterogeneity in the quality and quantity of the immune response. The functional evidence for T-lymphocyte function in jawless and cartilagenous fish is poor, while the bony fish seem to have many characteristics of a mammalian immune system. The organization and sequence of fish Ig genes also indicate that important events in the evolution of the immune system and the MHC occurred in the fish, but thus far there is no molecular evidence for recognizable MHC-like molecules in any fish. There is clearly an MHC in amphibians and birds with many characteristics like the MHC of mammals (a single genetic region encoding polymorphic class I and class II molecules) and evidence for polymorphic class I and class II molecules in reptiles. However, many details differ from the mammals, and it is not clear whether these reflect historical accident or selection for different lifestyles or environment. For example, the adult frog Xenopus has a vigorous immune system with many similarities to mammals, a ubiquitous class I molecule, but a much wider class II tissue distribution than human, mouse and chicken. The Xenopus tadpole has a much more restricted immune response, no cell surface class I molecules and a mammalian class II distribution. The axolotl has a very poor immune response (as though there are no helper T cells), a wide class II distribution and, for most animals, no cell surface class I molecule. It would be enlightening to understand both the mechanisms for the regulation of the MHC molecules during ontogeny and the consequences for the immune system and survival of the animals. These animals also differ markedly in the level of MHC polymorphism. Another difference from mammals is the presence of previously uncharacterized molecules. In Xenopus and reptiles, there are two populations of class I alpha chain on the surface of erythrocytes, those in association with beta 2m and those in association with a disulfide-linked homodimer.(ABSTRACT TRUNCATED AT 400 WORDS)

Monoclonal antibody differentiates chicken A system alloantigens

A monoclonal antibody (ISU-cA) was produced that recognized certain alloantigens of the chicken A blood group locus. Antigens produced by alleles A3, A4 and A8 were positive, and those produced by A2 and A5 were negative, by haemagglutination. The specificity of ISU-cA for chicken A blood group antigens was demonstrated by serologic analyses, genetic crosses and competitive inhibition of binding by anti-A alloantisera. To our knowledge, this is the first reported monoclonal antibody against a chicken blood group alloantigen system other than the B complex.

Ontogeny and expression of chicken A blood group antigens

Expression of chicken red blood cell (RBC) surface antigens was studied by using a monoclonal antibody (ISU-cA) specific for chicken A blood group antigens. Erythrocytes were examined from embryos of 3-18 days of incubation and from chicks at hatch up to 21 weeks of age. Specific antigens were detected on embryonic RBC surfaces by immunofluorescence as early as 3 days of incubation. Antigenic expression was examined by both haemagglutination and immunofluorescence and found to increase with age from embryos to mature birds. The antigen concentration on the cell surface was found to be affected by genotype; heterozygotes had an intermediate level of antigen between that of the two parental genotypes. These data confirm the co-dominance that is observed with most blood group antigens. Flow cytometric analysis allowed confirmation that the entire erythrocyte population gradually increased in antigenic expression over time, rather than having an antigen-negative subpopulation being replaced by a positive subpopulation.

Embryonic development of four different subsets of cholinergic neurons in rat cervical spinal cord

The developmental stage at which a neuron becomes committed to a neurotransmitter phenotype is an important time in its ontogenetic history. The present study examines when choline acetyltransferase (ChAT) is first detected within each of four different subsets of cholinergic neurons previously identified in the cervical enlargement of the spinal cord: namely, motor neurons, partition cells, central canal cluster cells, and dorsal horn neurons. By examining the temporal sequence of embryonic development of these cholinergic neurons, we can infer the relationships between ChAT expression and other important developmental events. ChAT was first detected reliably on embryonic day 13 (E13) by both biochemical and immunocytochemical methods, and it was localized predominantly within motor neurons. A second group of primitive-appearing ChAT-positive cells was detected adjacent to the ventricular zone on E14. These neurons seemed to disperse laterally into the intermediate zone by E15, and, on the basis of their location, were tentatively identified as partition cells. A third group of primitive ChAT-immunoreactive cells was detected on E16, both within and around the ventral half of the ventricular zone. By E17, some members of this "U"-shaped group appeared to have dispersed dorsally and laterally, probably giving rise to dorsal horn neurons as well as dorsal central canal cluster cells. Other members of this group remained near the ventral ventricular zone, most likely differentiating into ventral central canal cluster cells. Combined findings from the present study and a previous investigation of neurogenesis (Phelps et al.: J. Comp. Neurol. 273:459-472, '88), suggest that premitotic precursor cells have not yet acquired the cholinergic phenotype because ChAT is not detectable until after the onset of neuronal generation for each of the respective subsets of cholinergic neurons. However, ChAT is expressed in primitive bipolar neurons located within or adjacent to the germinal epithelium. Transitional stages of embryonic development suggest that these primitive ChAT-positive cells migrate to different locations within the intermediate zone to differentiate into the various subsets of mature cholinergic neurons. Therefore, it seems likely that spinal cholinergic neurons are committed to the cholinergic phenotype at pre- or early migratory stages of their development. Our results also hint that the subsets of cholinergic cells may follow different migration routes. For example, presumptive partition cells may use radial glial processes for guidance, whereas dorsal horn neurons may migrate along nerve fibers of the commissural pathway. Cell-cell interactions along such diverse migratory pathways could play a role in determining the different morphological, and presumably functional, phenotypes expressed by spinal cholinergic neurons.

Antigens similar to major histocompatibility complex B-G are expressed in the intestinal epithelium in the chicken

A monoclonal antibody directed against the erythrocytic B-G antigens of the major histocompatibility complex (MHC) of the chicken, an antiserum raised against purified erythrocytic B-G protein, and a cDNA probe from the B-G subregion were used to look for evidence of the expression of B-G genes in tissues other than blood. Evidence has been found in northern hybridizations, in immunoblots, and in immunolabeled cryosections for the presence of B-G-like antigens in the duodenal and caecal epithelia. Additional B-G-like molecules may be expressed in the liver as well. The B-G-like molecules in these tissues appear larger and somewhat more heterogeneous than the B-G antigens expressed on erythrocytes. Further characterization of these newly recognized B-G-like molecules may help to define a function for the enigmatic B-G antigens of the MHC. al. 1977; Miller et al. 1982, 1984; Salomonsen et al. 1987; Kline et al. 1988), and in the multiplicity of B-G restriction fragment patterns found in genomic DNA from different haplotypes (Goto et al. 1988; Miller et al. 1988; Chaussé et al. 1989). The B-G antigens have contributed, together with the B-F (class I) and B-L (class II) antigens, to the definition of over 27 B system haplotypes in experimental flocks (Briles et al. 1982). Yet the function of the B-G antigens remains entirely unknown. No mammalian counterparts have been identified, although the possibility remains that there may be similar antigens among the blood group systems of mammals. In an effort to define a function of the B-G antigens, a recently cloned B-G sequence (Miller et al. 1988; Goto et al. 1988) and antibodies to the B-G polypeptides (Miller et al. 1982, 1984) were used to examine other tissues for evidence of B-G expression.

Ultrastructural analysis of choline acetyltransferase-immunoreactive sympathetic preganglionic neurons and their dendritic bundles in rat thoracic spinal cord

We have used a monoclonal antibody against choline acetyltransferase (ChAT) to aid in the identification of sympathetic preganglionic neurons (SPNs) and to examine their ultrastructure in rat thoracic spinal cord. The clusters of ChAT-immunoreactive (ChAT-IR) preganglionic cell bodies and their distinctive bundles of dendrites give rise to a ladder-like appearance in horizontal light microscopic sections. This organization also produced a characteristic appearance of preganglionic neuropil when viewed electron microscopically. The intermediolateral (IML) nucleus contained numerous rostrocaudally oriented ChAT-IR dendrites. In addition, mediolaterally oriented ChAT-IR dendrites extended between the IML and the central autonomic region. Both the ChAT-IR dendrites and somata of preganglionic neurons were intimately associated with astroglial processes. The cell bodies were typically covered over a large proportion of their surface by a thin astrocytic sheath, and this was associated with a paucity of axon terminals forming axosomatic synapses. Instead, the vast majority of synapses upon SPNs were of the axodendritic type. The most frequently observed type of axon terminal contained numerous round, clear vesicles along with several dense-core vesicles (DCVs). In addition, some boutons contained a predominance of DCVs. Serial section analysis revealed that these apparently diverse morphological classes of synaptic boutons may simply represent variability of structure throughout a single terminal, with a greater proportion of DCVs being located distal to the synaptic specialization and a greater number of round, clear vesicles being present adjacent to the synapse. Analysis of the dendritic bundles revealed that individual dendrites, like the cell bodies, were often isolated from each other and the surrounding neuropil by astrocytic processes. This arrangement usually was interrupted only at regions of synaptic contact where astrocytic processes surrounded the synaptic complex as a whole. Thus, astroglial ensheathment of SPNs seems designed to minimize cross-talk between the bundled dendrites, as well as to isolate or segregate the diverse afferent inputs known to impinge on these cells.

B-G cDNA clones have multiple small repeats and hybridize to both chicken MHC regions

We used rabbit antisera to the chicken MHC erythrocyte molecule B-G and to the class I alpha chain (B-F) to screen lambda gt11 cDNA expression libraries made with RNA selected by oligo-dT from bone marrow cells of anemic B19 homozygous chickens. Eight clones were found to encode B-G molecules which hybridize with sequences in the chicken MHC as defined by congenic strains; the fusion proteins react with multiple immune but not preimmune sera, they select antibodies from the antisera to B-G, which then react with distinct erythrocyte B-G protein patterns, and they elicit antibodies from mice which in turn react with authentic B-G proteins. None of the clones represent a complete message, some--if not all--bear introns, and none of them match with any sequences presently stored in the data banks. The following new information did, however, emerge. At least two homologous transcripts are present in this homozygous chicken, thereby formally proving the existence of an expressed multigene family. The 3' ends (3'UT) are simple sequences with 80% nucleotide identity between clones, while the 5' ends (either coding or noncoding) are composed of multiple short repeats which are far less similar. These repeats could explain the bewildering variation in size of B-G proteins within and between haplotypes. Southern blots of genomic chicken DNA gave complex patterns for most probes, with many bands in common using different probes, but few bands in common between haplotypes. The sequences detected are all present in the MHC, based on the congenic lines CB and CC. Most of these sequences map into the B-G region, but some map into the B-F/B-L region as defined by the haplotypes B15, B21, and their apparently reciprocal recombinants B21r3 and B15r1.

The major histocompatibility complex in the chicken

The chicken B complex is the first non-mammalian MHC characterized at the molecular level. It differs from the human HLA and murine H-2 complexes in the small size of the class I (B-F) and class II (B-L) genes and their close proximity. This proximity accounts for the absence of recombination between B-F and B-L genes and leaves no space for class III genes. Moreover the B-F and B-L genes are tightly linked to unrelated genes absent from mammalian MHCs, such as the polymorphic B-G genes and a member of the G protein beta subunit family. This linkage could form the basis for resistance to viral-induced tumors associated with some B complex haplotypes.

The chicken major histocompatibility complex in disease resistance and poultry breeding

Numerous studies confirm that genes in the chicken major histocompatibility complex exert major genetic control over host resistance to autoimmune, viral, bacterial, and parasitic diseases. Examples of major histocompatibility complex associations with traits of growth and reproduction in the chicken are also available. Thus, the major effects of the major histocompatibility complex on the economically important traits of disease resistance, growth, and reproduction make the major histocompatibility complex a valuable subject for intensive analysis in agricultural species. This paper examines, as a model for integration of genetics and immunology, the research on the chicken major histocompatibility complex, which confirmed its role in genetic control of disease resistance, focusing on Marek's disease, a virally induced cancer. Current knowledge of associations of the chicken major histocompatibility complex with specific disease resistance, immune response, and other economic traits are selectively reviewed. Use of major histocompatibility complex typing in the poultry industry, including speculation about future applications, is presented.

Neurogenesis of basal forebrain cholinergic neurons in rat

The basal forebrain cholinergic system embodies a heterogeneous group of neurons distributed in the basal telencephalon that project topographically to the cortical mantle. We sought to examine the generation of these neurons to determine whether basal forebrain neurons have unique patterns of neurogenesis or, if, in contrast, they are born along general neurogenic gradients. The techniques of tritiated thymidine autoradiography and choline acetyltransferase (ChAT) immunocytochemistry were combined to determine the birthdays and neurogenic gradients of cholinergic cells in this region of rat brain. Cholinergic neurogenesis throughout the basal forebrain ranged from embryonic days 12 to 17 (E12-17). Neurogenesis in the nucleus basalis magnocellularis occurred over E12-16, with a peak day of generation on E13. The horizontal limb nucleus of the diagonal band which is located rostral to the nucleus basalis was generated over E12-17, with the majority of cells arising on E14-15. The rostral-most nuclei of the basal forebrain cholinergic system, the vertical limb of the diagonal band and the medial septum, were generated between E13-17, with peak days of neurogenesis on E15 and E15-16, respectively. These results were evaluated quantitatively and demonstrated that the basal forebrain cholinergic neurons were generated along the general caudal-to-rostral gradient previously described for all neurons in this brain region. The results of this study, in combination with those of similar investigations, emphasize that position-dependent epigenetic factors appear to be more potent determinants of the time of neuronal origin than factors which influence a cell's transmitter phenotype.

The generation and differentiation of cholinergic neurons in rat caudate-putamen

By combining [3H]thymidine autoradiography with choline acetyltransferase (ChAT) immunocytochemistry, we have determined the generation pattern of the large cholinergic neurons in the neostriatum. All of these neurons are produced between embryonic days 12 and 17 (E12-E17), with 75% of them being born between E13 and 15. Cholinergic neurons appeared to be among the earliest cells produced in the neostriatum when compared with previous generation studies of all neurons in the rat caudate-putamen. The caudal-to-rostral neurogenic gradient reported in previous investigations of all neurons was the only spatiotemporal gradient observed for cholinergic neurons. The generation peak for these cells was E13 caudally, and E15 rostrally. Additional immunocytochemical studies detected ChAT immunoreactivity within somata and primary dendrites of 1 day postnatal (1 dpn) rat neostriatum, and subsequently demonstrated a dramatic increase in the intensity of reaction product and the complexity of dendritic arborizations by 14 dpn. Large ChAT-positive neurons of the basal forebrain contained within the same specimens appeared to differentiate their cholinergic phenotype earlier than those in the neostriatum. However, recent generation studies of basal forebrain neurons combined with the present results have demonstrated that both cholinergic populations are produced simultaneously along the same neurogenic gradients. This then represents an example of cholinergic projection (basal forebrain system) and local circuit (neostriatum) neurons that share similar generation patterns but differ with respect to sequences of transmitter phenotype expression. Thus, for cholinergic forebrain neurons, a cell's position along the neurogenic gradient and its transmitter phenotype appear to be more closely associated with its birth date than its ultimate projection or rate of differentiation.

Generation patterns of four groups of cholinergic neurons in rat cervical spinal cord: a combined tritiated thymidine autoradiographic and choline acetyltransferase immunocytochemical study

This report examines the generation of cholinergic neurons in the spinal cord in order to determine whether the transmitter phenotype of neurons is associated with specific patterns of neurogenesis. Previous immunocytochemical studies identified four groups of choline acetyltransferase (ChAT)-positive neurons in the cervical enlargement of the rat spinal cord. These cell groups vary in both somatic size and location along the previously described ventrodorsal neurogenic gradient of the spinal cord. Thus, large (and small) motoneurons are located in the ventral horn, medium-sized partition cells are found in the intermediate gray matter, small central canal cluster cells are situated within lamina X, and small dorsal horn neurons are scattered predominantly through laminae III-V. The relationships among the birthdays of these four subsets of cholinergic neurons have been examined by combining 3H-thymidine autoradiography and ChAT immunocytochemistry. Embryonic day 11 was the earliest time that neurons were generated within the cervical enlargement. Large and small ChAT-positive motoneurons were produced on E11 and 12, with 70% of both groups being born on E11. ChAT-positive partition cells were produced between E11 and 13, with their peak generation occurring on E12. Approximately 70% of the cholinergic central canal cluster and dorsal horn cells were born on E13, and the remainder of each of these groups was generated on E14. Other investigators have shown that all neurons within the rat cervical spinal cord are produced in a ventrodorsal sequence between E11 and E16. In contrast, ChAT-positive neurons are born only from E11 to E14 and are among the earliest cells generated in the ventral, intermediate, and dorsal subdivisions of the spinal cord. However, all cholinergic neurons are not generated simultaneously; rather their birthdays are correlated with their positions along the ventrodorsal gradient of neurogenesis. The fact that large motoneurons and medium-sized partition cells are born before small central canal cluster and dorsal horn cells would appear to support the generalization that large neurons are generated before small ones. However, the location of spinal cholinergic neurons within the neurogenic gradient seems to be more importantly associated with the time of cell generation than somal size. For example, when large and small motoneurons located at the same dorsoventral spinal level are compared, both sizes of cells are generated at the same time and in similar proportions.(ABSTRACT TRUNCATED AT 400 WORDS)

A comparison of the localization of choline acetyltransferase and glutamate decarboxylase immunoreactivity in rat cerebral cortex

The neurotransmitter-synthesizing enzymes choline acetyltransferase and glutamate decarboxylase were localized immunocytochemically at the light microscopic level. Their respective laminar distributions were compared in 17 different cytoarchitectural areas, comprising limbic and neocortical regions of rat cerebral cortex. The immunoreactive intensities within these areas were measured with an image analysis system and dark-field optics. Choline acetyltransferase and glutamate decarboxylase immunoreactivity displayed distinctive distribution patterns throughout the cerebrum. In general, limbic cortex showed greater intensity of both choline acetyltransferase and glutamate decarboxylase immunoreactivity than neocortex. For example, choline acetyltransferase immunoreactivity in pyriform and retrosplenial cortex was 54% and 29% greater, respectively, than in neocortex, and glutamate decarboxylase immunoreactivity in the same cortical areas was 5% and 17% greater, respectively. In addition to these regional differences, the marked variations of choline acetyltransferase and glutamate decarboxylase immunostaining were characterized as either coincidental or complementary when comparing their laminar distributions. The laminar pattern and relative intensities of choline acetyltransferase and glutamate decarboxylase immunostaining were coincident in some layers of all cortical regions. For example, both choline acetyltransferase and glutamate decarboxylase immunoreactive intensities were high in cellular layers II and IV of the entorhinal cortex. In contrast, examples of complementary choline acetyltransferase and glutamate decarboxylase immunoreactive patterns were observed in retrosplenial cortex and neocortex. In neocortex, layers III and part of V were intensely glutamate decarboxylase-positive, whereas these same layers were less intensely choline acetyltransferase immunoreactive than the intervening layer IV and upper part of V. Quantitatively, choline acetyltransferase immunoreactivity in layers IV and upper V was 27-37% greater than adjacent layers II and deep V. The glutamate decarboxylase immunostaining pattern was complementary in that layer IV was 19-23% less intensely stained than adjacent layers III and V. Our results demonstrate that terminals immunoreactive for choline acetyltransferase and glutamate decarboxylase, and presumably the synaptic terminals that respectively use acetylcholine or gamma-aminobutyric acid as their neurotransmitters, are distributed in distinct laminar patterns that are strategically situated for modulating either afferent information in the case of cholinergic terminals or efferent transmission for GABAergic endings.(ABSTRACT TRUNCATED AT 400 WORDS)

Isolation of a cDNA clone from the B-G subregion of the chicken histocompatibility (B) complex

The B-G antigens are highly polymorphic antigens encoded by genes located within the major histocompatibility complex (MHC) of the chicken, the B system. The B-G antigens of the chicken MHC are found only on erythrocytes and correspond to neither MHC class I nor class II antigens. Several clones were selected from a lambda gt11 erythroid cell expression library by means of rabbit antisera prepared against a purified, denatured B-G antigen. One clone chosen for further study, lambda bg28, was confirmed as a B-G subregion cDNA clone by the results obtained through using it as a nucleic acid hybridization probe. In Northern hybridizations lambda bg28 anneals specifically with erythroid cell mRNA. In Southern blot analyses the lambda bg28 clone could be assigned to the B system-bearing microchromosome of the chicken karyotype on the basis of its hybridization to DNA from birds disomic, trisomic, and tetrasomic for this microchromosome. The cDNA clone was further mapped to the B-G subregion on the basis of its pattern of hybridization with DNA from birds of known B region recombinant haplotypes. Southern blot analyses of the hybridization of lambda bg28 with genomic DNA from birds of known haplotypes strongly suggest that the B-G antigens are encoded by a highly polymorphic multigene family.

Biochemical confirmation of recombination within the B-G subregion of the chicken major histocompatibility complex

Analysis of the B-G antigens of eight chicken major histocompatibility complex (B) system recombinant haplotypes by high resolution two-dimensional gel electrophoresis has provided evidence for the transfer of the complete B-G subregion in seven cases. In the eighth, a partial duplication within the B-G subregion appears to have occurred. In this recombinant, the entire array of polypeptides associated with one parental allele, B-G23, is expressed together with nearly the entire array of B-G polypeptides of the other parental haplotype, B2. This compound polypeptide pattern corroborates the serological evidence for a partial duplication within the B-G subregion and provides indirect evidence for the existence of multiple loci within B-G and for a means by which polymorphism may be introduced into the chicken major histocompatibility complex.

AEV-transformed erythroleukemia cell induced differentiation: expression of specific cell membrane antigenic molecules

A simultaneous decay of the expression of Im 140 kDa, Im 150 kDa and Im 160 kDa high MW membrane antigens, concomitant with the cell proliferation arrest, was observed during erythropoietin induced differentiation of ts 34 AEV-transformed erythroid cells cultivated at the restrictive temperature. Expression of embryo-immature antigens was maintained during induced differentiation of erythroleukemia cells, but their MW shifted from 50 to 48 kDa, which corresponds to the MW of embryo-immature antigens detected on normal erythroid cells. In the absence of erythropoietin at the restrictive temperature, conditions under which the ts 34 AEV-transformed erythroid cells fail to differentiate and maintain their capacity to proliferate, the expression of high MW antigens as well as the expression of embryo-immature antigens remained unaffected. Therefore, it is shown that the expression of specific membrane antigens is modulated under conditions rendering the erythroleukemia cell differentiation process possible.

The chicken erythrocyte-specific MHC antigen. Characterization and purification of the B-G antigen by monoclonal antibodies

Mouse monoclonal antibodies with B-G antigen (major histocompatibility complex class IV) specificity were obtained after immunization with erythrocytes or partially purified B-G antigen. The specificities of the hybridoma antibodies were determined by precipitation of B-G antigens from 125I-labeled chicken erythrocyte membranes (CEM) followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and autoradiography. The B-G antigen had an approximate molecular mass of 46-48 kd in reduced samples, depending on the haplotype, and in unreduced samples contained either dimers (85 kd), when labeled erythrocytes were the antigen source, or trimers (130 kd), when B-G was purified and precipitated from CEM. The B-G antigen was unglycosylated as studied by in vitro synthesis in the presence or absence of tunicamycin, binding experiments with lectin from Phaseolus limensis, and treatment of purified B-G antigen with Endoglycosidase-F or trifluoromethanesulfonic acid. Two-way sequential immunoprecipitation studies of erythrocyte membrane extracts with anti-B-G alloantisera and monoclonal antibodies revealed only one population of B-G molecules. Pulse-chase experiments have shown B-G to be synthesized as a monomer, with dimerization taking place after 20-30 min. No change in the monomer's molecular mass due to posttranslational modifications was revealed. The antigen was purified from detergent extract of CEM by affinity chromatography with a monoclonal antibody, and then reduced and alkylated and affinity-purified once more. Finally, reverse-phase chromatography resulted in a pure product. The B-G antigen was identified in the various fractions by rocket immunoelectrophoresis. The final product was more than 99% pure, as estimated by SDS-PAGE analysis followed by silver stain of proteins. The yield from the affinity chromatography step was 3-4 micrograms B-G/ml blood, calculated from Coomassie-stained SDS-PAGE of B-G using ovalbumin standards. The monoclonal antibodies were also used to identify the B-G (class IV) precipitation arc in crossed immunoelectrophoresis. No common precipitate with the B-F (class I) antigen was observed.

Molecular analysis of the chicken major histocompatibility complex gene and gene products

New technologies are enabling researchers to conduct analysis of the molecular structure of the genes and gene products of the major histocompatibility complex (MHC). Two of these new technologies are the production of monoclonal antibodies by hybridomas and analysis of deoxyribonucleic acid (DNA) by restriction fragment length polymorphisms (RFLP) on Southern blots. Monoclonal antibodies, because of their exquisite specificity, can be used to isolate purified MHC antigens for further study. The RFLP analysis can be used to examine differences in the MHC at the DNA level. This paper describes the two aforementioned technologies and their application to molecular analysis of the chicken MHC.

An immunocytochemical study of choline acetyltransferase-containing neurons and axon terminals in normal and partially deafferented hippocampal formation

Monoclonal antibodies to the acetylcholine synthesizing enzyme, choline acetyltransferase (ChAT), have been used to study putative cholinergic structures in immunocytochemical preparations of normal rat hippocampal formation and of hippocampal formation deprived of its septal innervation. Small numbers of ChAT-positive (ChAT+) neuronal somata were observed scattered throughout the septotemporal extent of the normal hippocampal formation. They were most common in stratum lacunosum-moleculare of regio superior, but were also found in various layers of the dentate gyrus and occasionally in the remaining hippocampal laminae. In addition, light microscopy demonstrated that ChAT+ terminal fields in normal hippocampal formation were organized in discrete bands and laminae. Pronounced dense bands were observed: immediately superficial to stratum granulosum; deep to stratum pyramidale; and at the border between stratum radiatum and stratum lacunosum-moleculare. In the dentate gyrus, ChAT+ staining was pronounced in the hilus at temporal levels, but only moderate staining occurred in the anterior hilus and throughout the molecular layer. A close correspondence was observed in the density and distribution of ChAT+ immunoreactivity and acetylcholinesterase staining. Electrolytic lesions of the medial septal nucleus/diagonal band complex had no effect on the occurrence of ChAT+ somata, but virtually abolished the ChAT+ laminar staining pattern and eliminated all but occasional small patches of ChAT+ terminals. These results confirm that the vast majority of hippocampal cholinergic terminals originate either from neurons of the medial septum/diagonal band complex or from fibers of passage. The newly observed intrinsic hippocampal neurons can account for at least some of the ChAT activity remaining after septal lesions, and they apparently contribute to the cholinergic innervation of the hippocampal formation.

Chick embryonic erythrocyte antigen--tissues sharing expression

There is an antigenic glycoprotein (Mr 48 kD) present on the surfaces of erythrocytes of embryonic and young chickens that cannot be detected on the circulating erythrocytes in adult birds. This antigen, generally defined by this differential expression, has been thought to be associated with the maturation of hematopoietic tissues. We now present evidence, based on the use of a monoclonal antibody, maEE1, and the characteristic pattern of this glycoprotein on two-dimensional (2D) gels, that this antigen, which we have named chickEE, is expressed in a number of other embryonic and adult tissues. Immunofluorescent labeling of cryosections and flow-cytometric analysis of cells labeled with maEE1 have revealed the presence of chickEE in the retina (present in all layers), in muscle tissues (present in the endomysium and within the vascular endothelium), in the liver (especially evident on the lateral surface of hepatocytes and within the sinusoids), on epithelia such as the gut and kidney tubule epithelium and within lymphoid organs (present on bursacytes, splenocytes, thymocytes and peripheral leukocytes, and again within the endothelium) of young and adult animals. The 2D gel patterns of chickEE derived from embryonic tissues (retina, hind limb, thymus and bursa) and the adult tissues (retina and spleen) are very similar to that of the embryonic erythrocyte. Thus, the extended reactivity of the monoclonal antibody to chickEE, maEE1, with additional tissues is, in at least the tissues examined, based on the presence of the chickEE glycoprotein and not on incidental cross-reactivity. The evidence presented in this paper for the widely-shared expression of chickEE antigen makes it necessary to reconsider the function of this component of the cell surface.

Immunocytochemical localization of choline acetyltransferase in rat ventral striatum: a light and electron microscopic study

The ventral striatum, previously defined as including the nucleus accumbens, substriatal grey, olfactory tubercle and striatal cell bridges has been examined in an immunocytochemical study with monoclonal antibodies to choline acetyltransferase (ChAT) in order to identify putative cholinergic neurons and synaptic junctions within the region. Light microscopy revealed ChAT-positive neurons with similar morphological characteristics in all divisions of ventral striatum. The somata of immunoreactive neurons were round or elongated in shape, approximately 10 X 21 microns in size and had two to four dendrites that coursed long distances and occasionally branched. Electron microscopy of ChAT-positive neurons in substriatal grey initially studied by light microscopy revealed that unlabelled boutons occasionally formed synapses with immunoreactive somata and proximal dendrites, but were more numerous along distal dendrites. Light microscopy demonstrated that ventral striatal neuropil contained numerous ChAT-positive fibres and punctate structures that varied in concentration from moderate to very dense. The lateral border of the substriatal grey and the area within, and adjacent to, all islands of Calleja exhibited the most dense ChAT-positive punctate staining. Additionally, the medial portion of nucleus accumbens was more densely ChAT-positive than the lateral, and the olfactory tubercle displayed laminar variations of immunoreaction product. Counterstained immunocytochemical specimens demonstrated that some areas of dense ChAT-positive punctate staining were associated with clusters of ChAT-negative, medium-sized neurons. Furthermore, electron microscopic observations of substriatal grey revealed that ChAT-positive dense regions were associated with numerous immunoreactive boutons, some of which established synapses with unlabelled somata, dendritic shafts and spines. These results suggest that the densely ChAT-positive neuropil areas within ventral striatum receive more cholinergic innervation than the more lightly stained neuropil areas. There are numerous similarities in the morphological characteristics of ChAT-positive neurons and synapses observed in ventral striatum when compared with those previously described in dorsal striatum. However, some differences were observed, such as smaller somal sizes in ventral, as contrasted with dorsal striatum, and a substantial variation in ChAT-positive fibre and punctate neuropil staining seen within the ventral but not the dorsal striatum. Such differences suggest that the ventral striatum may exhibit greater heterogeneity of cholinergic function than the dorsal striatum.

An improved method of toluidine blue counterstaining of neurons in immunocytochemical preparations

Immunocytochemical methods can identify individual neurons and processes made immunoreactive by virtue of the antigens they contain. However, frequently it is also useful to visualize surrounding nonimmunoreactive cells, but immunocytochemical procedures often interfere with the quality of subsequent counterstaining. This report describes an improved method of counterstaining immunocytochemical specimens with either aged (at least 1 year) or concentrated solutions of toluidine blue. This technique combines well with immunocytochemical preparations of at least two antigens, i.e., choline acetyltransferase and glutamic acid decarboxylase, to delineate nonimmunoreactive somata. Additionally, a method of photographing these color preparations is described that, by the use of an appropriate filter, allows one to illustrate sections essentially with and without blue counterstain in black and white photomicrographs.

Immunocytochemical localization of choline acetyltransferase within the rat neostriatum: a correlated light and electron microscopic study of cholinergic neurons and synapses

Monoclonal antibodies to choline acetyltransferase (ChAT) were used in an immunocytochemical study to characterize putative cholinergic neurons and synaptic junctions in rat caudate-putamen. Light microscopy (LM) revealed that ChAT-positive neurons are distributed throughout the striatum. These cells have large oval or multipolar somata, and exhibit three to four primary dendrites that branch and extend long distances. Quantitative analysis of counterstained preparations indicated that ChAT-positive neurons constitute 1.7% of the total neuronal population. Electron microscopy (EM) of immunoreactive neurons initially studied by LM revealed somata characterized by deeply invaginated nuclei and by abundant amounts of organelle-rich cytoplasm. Surfaces of ChAT-positive neurons are frequently smooth, but occasional somatic protrusions and dendritic spines occur. Although infrequently observed, axons of ChAT-positive neurons branch, receive synapses, and become myelinated. Unlabeled boutons make both symmetrical and asymmetrical synapses with ChAT-positive somata and proximal dendrites, but are more numerous on distal dendrites. In addition, some unlabeled terminals form asymmetrical synapses with ChAT-positive somata and dendrites that are distinguished by prominent subsynaptic dense bodies. Light microscopy demonstrated a dense distribution of ChAT-positive fibers and punctate structures in the striatum, and these structures appear to correlate, respectively, with labeled preterminal axons and presynaptic boutons identified by EM. ChAT-positive boutons contain pleomorphic vesicles, and make symmetrical synapses primarily with unlabeled dendritic shafts. Furthermore, they establish synaptic contacts with somata, dendrites and axon initial segments of unlabeled neurons that ultrastructurally resemble medium spiny neurons. These observations, together with the results of other investigations, suggest that medium spiny GABAergic projection neurons receive a cholinergic innervation that is probably derived from ChAT-positive striatal cells. The results of this study also indicate that cholinergic neurons within caudate-putamen belong to a single population of cells that have large somata and extensive sparsely spined dendrites. Such neurons, in combination with dense concentrations of ChAT-positive fibers and terminals, are the likely basis for the large amounts of ChAT and acetylcholine detected biochemically within the neostriatum.

Chicken developmental antigens: analysis of erythroid populations with monoclonal antibodies

Fusions were performed between the mouse PAI myeloma cell line and spleen cells from Balb/c mice immunized with intact erythrocytes from 1-day Cornell K-strain White Leghorn chickens. Following single cell cloning, four hybridoma clones were found to secrete erythroid specific monoclonal antibodies. Based on its pattern of reactivity, the antibody (IgG2a, kappa) secreted by clone 10C6 detects a specific avian oncodevelopmental antigen associated with the hematopoietic system: chicken fetal antigen (CFA). Two other clones, designated as 3F12 and 4C2, produced antibodies (IgM, kappa) that recognize another avian developmental antigen: chicken adult antigen (CAA). A fourth clone, 9F9, produced an antibody (IgM, kappa) that reacts with all peripheral erythrocytes from both Japanese quail and chicken regardless of age. Clone 10C6 antibody apparently detects an erythrocyte specific (ES) determinant of CFA associated with determinant #8 while antibodies of clones 3F12 and 4C2 recognize a chicken specific determinant of CAA. Analysis by complement mediated microcytotoxicity indicated that the epitopes detected by 10C6 vs 3F12 and 4C2 antibodies were expressed on erythrocytes in a reciprocal fashion during development. Furthermore, strain variations in the incidence of erythrocytes carrying these epitopes were observed. The usefulness of these monoclonal antibodies for the study of erythroid populations is discussed.

Immunocytochemical localization of choline acetyltransferase in rat cerebral cortex: a study of cholinergic neurons and synapses

Choline acetyltransferase (ChAT), the acetylcholine-synthesizing enzyme and a definitive marker for cholinergic neurons, was localized immunocytochemically in the motor and somatic sensory regions of rat cerebral cortex with monoclonal antibodies. ChAT-positive (ChAT+) varicose fibers and terminal-like structures were distributed in a loose network throughout the cortex. Some immunoreactive cortical fibers were continuous with those in the white matter underlying the cortex, and many of these fibers presumably originated from subcortical cholinergic neurons. ChAT+ fibers appeared to be rather evenly distributed throughout all layers of the motor cortex, but a subtle laminar pattern was evident in the somatic sensory cortex, where lower concentrations of fibers in layer IV contrasted with higher concentrations in layer V. Electron microscopy demonstrated that immunoreaction product was concentrated in synaptic vesicle-filled profiles and that many of these structures formed synaptic contacts. ChAT+ synapses were present in all cortical layers, and the majority were of the symmetric type, although a few asymmetric ones were also observed. The most common postsynaptic elements were small to medium-sized dendritic shafts of unidentified origin. In addition, ChAT+ terminals formed synaptic contacts with apical and, probably, basilar dendrites of pyramidal neurons, as well as with the somata of ChAT-negative nonpyramidal neurons. ChAT+ cell bodies were present throughout cortical layers II-VI, but were most concentrated in layers II-III. The somata were small in size, and the majority of ChAT+ neurons were bipolar in form, displaying vertically oriented dendrites that often extended across several cortical layers. Electron microscopy confirmed the presence of immunoreaction product within the cytoplasm of small neurons and revealed that they received both symmetric and asymmetric synapses on their somata and proximal dendrites. These observations support an identification of ChAT+ cells as nonpyramidal intrinsic neurons and thus indicate that there is an intrinsic source of cholinergic innervation of the rat cerebral cortex, as well as the previously described extrinsic sources.

The morphology and distribution of neurons containing choline acetyltransferase in the adult rat spinal cord: an immunocytochemical study

A monoclonal antibody to choline acetyltransferase (ChAT), the acetylcholine (ACh)-synthesizing enzyme, has been used to localize ChAT within neurons in immunocytochemical preparations of adult rat spinal cord. Morphological details of known cholinergic spinal neurons are presented in this study, and previously unidentified ChAT-containing neurons are also described. Immunoreaction product was present within cell bodies, dendrites, axons, and axon terminals, thereby allowing comprehensive descriptions of the distribution of ChAT-positive neurons and the interrelationships of their processes. In the ventral horn, ChAT-positive motoneurons were located in the medial, central, and lateral motor columns, and their dendrites formed elaborate longitudinal and transverse ChAT-positive bundles. These bundles were present throughout the rostrocaudal extent of the spinal cord. In the central gray matter, small ChAT-positive cell bodies were clustered around the central canal. Small longitudinal fascicles of immunoreactive processes were also observed in this region adjacent to the ependymal layer. The intermediate gray matter of virtually the entire spinal cord was spanned by medium to large ChAT-positive multipolar cells termed partition neurons. At autonomic spinal levels, partition neurons were intermingled with other immunoreactive cells that were identified as preganglionic sympathetic or parasympathetic neurons because of their locations and morphological characteristics. In the sympathetic system, four groups of ChAT-positive neurons were observed; the principal intermediolateral nucleus (ILp) in the lateral horn, the central autonomic cell column (CA) dorsal to the central canal, the intercalated nucleus (IC) located between ILp and CA, and the funicular intermediolateral neurons (ILf) in the white matter lateral to the ILp. The dendrites of ILp and CA neurons formed substantial longitudinal bundles within each group, as well as transverse bundles between the groups that resembled the rungs of a ladder. ChAT-positive cell bodies were also present in the dorsal horn, and those located in laminae III-V extended dendrites dorsally into a longitudinal plexus within lamina III.