Structures and activation mechanism of the Gabija anti-phage system

Prokaryotes have evolved intricate innate immune systems against phage infection1-7. Gabija is a highly widespread prokaryotic defence system that consists of two components, GajA and GajB8. GajA functions as a DNA endonuclease that is inactive in the presence of ATP9. Here, to explore how the Gabija system is activated for anti-phage defence, we report its cryo-electron microscopy structures in five states, including apo GajA, GajA in complex with DNA, GajA bound by ATP, apo GajA-GajB, and GajA-GajB in complex with ATP and Mg2+. GajA is a rhombus-shaped tetramer with its ATPase domain clustered at the centre and the topoisomerase-primase (Toprim) domain located peripherally. ATP binding at the ATPase domain stabilizes the insertion region within the ATPase domain, keeping the Toprim domain in a closed state. Upon ATP depletion by phages, the Toprim domain opens to bind and cleave the DNA substrate. GajB, which docks on GajA, is activated by the cleaved DNA, ultimately leading to prokaryotic cell death. Our study presents a mechanistic landscape of Gabija activation.

Structural and Ontogenetic Relationships of Rat Lung Surfactant Apoproteins

Glycoproteins of molecular weights (MW) of 38,000, 32,000, and 26,000 are found in surfactant isolated from rat lungs. These proteins were further examined for their specificity to pulmonary surfactant, structural and metabolic interrelationships, and relation to the ontogenesis of pulmonary surfactant. With ultracentrifugations in salt and sucrose density gradients, a preparation of pulmonary surfactant was isolated from rat lung lavage fluid, which was rich in surfactant lipids (phosphatidylcholine and phosphatidylglycerol), and contained exclusively the 38,000-, 32,000-, 26,000-, and 10,000- to 12,000-dalton proteins. The 38,000-, 32,000-, and 26,000-dalton proteins are not serum proteins. Using an antiserum specific for the combined 38,000-, 32,000-, and 26,000-dalton proteins and the immunoperoxidase technique, the source of one or more of these three proteins was found to be alveolar epithelial type II cells, the cells involved in the synthesis and secretion of pulmonary surfactant. These proteins, when dissociated from lipids, show considerable self-association and form homopolymers. On isoelectric focusing, these proteins show considerable charge heterogeneity, which, in large part, is due to terminally linked sialic acid residues. Partial proteolysis of these proteins and subsequent analyses of the released polypeptides suggest the existence of large segments of homology between the 38,000-, and 32,000-dalton proteins. The relationship of the 38,000-, and 32,000-dalton proteins with the 26,000-, and 10,000- to 12,000-dalton proteins is not clear as yet. The results of protein analyses of purified tubular myelin and of lamellar bodies suggest that the 26,000-dalton protein may be derived extracellularly, possibly from other surfactant proteins by the action of enzymes present in the alveolar lining layer. We observed no reactivity of the antibody raised against the 38,000-, 32,000-, and 26,000-dalton proteins with the 10,000- to 12,000-dalton protein. The 38,000-, 32,000-, and 26,000-dalton proteins appear during fetal lung maturation at the same gestational time as the surfactant is known to appear, and their combined content increases thereafter in fetal lungs and in amniotic fluid. It appears that the less glycosylated (32,000-dalton protein) of the 38,000- and 32,000-dalton proteins appears first during fetal lung development.

Detection of four distinct groups of hen egg allergens binding IgE in the sera of children with egg allergy

BACKGROUND

There appears to be a lack of agreement in the literature on the allergenicity of hen egg proteins. This may be partly due to the use of impure proteins in some cases. Egg yolk proteins have also been largely ignored in such studies. We therefore set out to determine, using especially purified proteins, their relative allergenicity, and to observe whether there were any relationships between their potency and the sensitivity of patients to them.

METHODS AND RESULTS

The sera of 40 patients with clinically observed hen egg hypersensitivity were tested for specific IgE binding to purified egg white and egg yolk proteins using the radioallergosorbent test (RAST). Statistical treatment by correspondence analysis of the percent radioactive uptakes in the RAST to the 8 proteins demonstrated that there were four distinct groups of patients reacting in a similar way to four discrete sets of proteins.

CONCLUSIONS

The first three sets of allergens consisted of egg white proteins as follows: firstly, lysozyme and ovalbumin; secondly, ovomucoid; and thirdly, ovomucin. The fourth set contained the egg white protein ovotransferrin and the egg yolk proteins apovitellenins I and VI and phosvitin. The existence of patient groups may explain why various workers have reported different allergens to be important in egg hypersensitivity. A sufficiently large number of patients must be examined so as to give a representative distribution across each group, otherwise the results may be biased towards one allergen.

PspA protects Streptococcus pneumoniae from killing by apolactoferrin, and antibody to PspA enhances killing of pneumococci by apolactoferrin [corrected]

Lactoferrin is an important component of innate immunity through its sequestration of iron, bactericidal activity, and immune modulatory activity. Apolactoferrin (ALF) is the iron-depleted form of lactoferrin and is bactericidal against pneumococci and several other species of bacteria. We observed that lactoferricin (LFN), an 11-amino-acid peptide from the N terminus of lactoferrin, is bactericidal for Streptococcus pneumoniae. Strains of S. pneumoniae varied in their susceptibility to ALF. Lactoferrin is bound to the pneumococcal surface by pneumococcal surface protein A (PspA). Using mutant PspA(-) pneumococci of four different strains, we observed that PspA offers significant protection against killing by ALF. Knockout mutations in genes for two other choline-binding proteins (PspC and PcpA) did not affect killing by ALF. PspA did not have to be attached to the bacterial surface to inhibit killing, because the soluble recombinant N-terminal half of PspA could prevent killing by both ALF and LFN. An 11-amino-acid fragment of PspA was also able to reduce the killing by LFN. Antibody to PspA enhanced killing by lactoferrin. These findings suggested that the binding of ALF to PspA probably blocks the active site(s) of ALF that is responsible for killing.

Specificity of IgG and IgE antibodies against plant and insect glycoprotein glycans determined with artificial glycoforms of human transferrin

Cross-reactive carbohydrate determinants of plants are essentially a mixture of N-glycans containing beta1,2-xylose and core alpha1,3-fucose, the latter also found in insect glycoproteins. To determine the relative contributions of these two sugar residues to antibody binding, we prepared an array of glycomodified forms of human apo-transferrin. Using core-alpha1, 3-fucosyltransferase (EC 2.4.1.214) and beta1,2-xylosyltransferase (EC 2.4.2.38) recombinantly expressed in Pichia pastoris and suitable glycosidases, glycoforms containing either only fucose (MMF), only xylose (MMX), both (MMXF), or neither (MM) linked to the common pentasaccharide core were generated. Additional glycoforms were obtained by enzymatic removal of the alpha1,3-linked mannosyl residue. These transferrin glycoforms served to define the binding specificity of antibodies in western blot, ELISA, and inhibition ELISA. Rabbit anti-horseradish peroxidase serum bound to both the fucosylated (MMF) and the xylosylated (MMX) glycoforms. Inhibition studies indicated two independent highly specific populations reacting with either of the two epitopes. In contrast, the monoclonal antibody YZ1/2.23 appears to recognize a larger structure including both the fucosyl and the xylosyl residue. The mannose-deficient glycoform was a poorer inhibitor for both antibodies. Terminal GlcNAc residues prevented antibody binding. Rabbit anti-bee venom serum reacted with fucosylated forms (MMF and MMXF) only. Experiments with sera from allergic patients suggest that glycomodified human transferrin, especially the MMXF glycoform, is a suitable reagent for the detection of antibodies against cross-reactive carbohydrate determinants. Within the panel studied, several sera contained high levels of fucose-reactive IgE but only a few sera showed any binding to MMX-transferrin.

The crystal structure of staphylococcal enterotoxin H: implications for binding properties to MHC class II and TcR molecules

The X-ray structure of the superantigen staphylococcal enterotoxin H (SEH) has been determined at 1.69 A resolution. In this paper we present two structures of zinc-free SEH (apoSEH) and one zinc-loaded form of SEH (ZnSEH). SEH exhibits the conventional superantigen (SAg) fold with two characteristic domains. In ZnSEH one zinc ion per SEH molecule is bound to the C-terminal beta-sheet in the region implicated for major histocompatibility complex class II (MHC class II) binding in SEA, SED and SEE. Surprisingly, the zinc ion has only two ligating amino acid residues His206 and Asp208. The other ligands to the zinc ion are two water molecules. An extensive packing interaction between two symmetry-related molecules in the crystal, 834 A(2)/molecule, forms a cavity that buries the zinc ions of the molecules. This dimer-like interaction is found in two crystal forms. Nevertheless, zinc-dependent dimerisation is not observed in solution, as seen in the case of SED. A unique feature of SEH as compared to other staphylococcal enterotoxins is a large negatively charged surface close to the Zn(2+) site. The interaction of SEH with MHC class II is the strongest known among the staphylococcal enterotoxins. However, SEH seems to lack a SEB-like MHC class II binding site, since the side-chain properties of structurally equivalent amino acid residues in SEH and those in SEB-binding MHC class II differ dramatically. There is also a structural flexibility between the domains of SEH. The domains of two apoSEH structures are related by a 5 degrees rotation leading to at most 3 A difference in C(alpha) positions. Since the T-cell receptor probably interacts with both domains, SEH by this rotation may modulate its binding to different TcR Vbeta-chains.

Intratracheally applied rSP-C surfactant exhibits no anaphylactic shock reactions in a guinea pig model of acute lung hypersensitivity

The effect of the intratracheal administration of the recombinant SP-C surfactant apoprotein (rSP-C) with phospholipids (PL) in comparison to an ovalbumin induced anaphylactic shock reaction was studied in guinea pigs lungs. Narcotized guinea pigs were challenged by intratracheal administration on test day 24/25 once with a suspension of rSP-C/PL (reconstituted suspension). These animals were priorily sensitized on test day 1, 3 and 5 intraperitoneally with rSP-C/PL suspension or with Ovalbumin (OV) respectively. The following groups were used to assess the anaphylactic lung shock symptoms: group 1: positive control, 1 mg/kg OV protein, 2 ml/kg application volume, (Appl. vol.), N: 5 animals; group 2: 1 mg rSP-C/50 mg PL/0.5 ml/kg Appl. vol., N: 10; group 3: 2 mg rSP-C/100 mg PL/1.0 ml/kg Appl. vol., N: 10; group 4: 4 mg rSP-C/200 mg PL/2.0 ml/kg Appl. vol., N: 10. Clinical signs, mortality, lung weights and histopathological changes were evaluated. Additionally the lungs were investigated immunohistologically with polyclonal antibodies against rSP-C to determine the pulmonary distribution of the intratracheal applied rSP-C. In the OV-treated positive control group, all animals died within 4 minutes after intratracheal challenge, while only 1 animal of group 4 died probably due to an narcosis related respiratory arrest. In the rSP-C/PL treated groups, the lung weights showed a dose-related increase, but nevertheless all these rSP-C-treated groups showed a significant lower lung weight in comparison to the OV treated positive control group. The histopathology assessment of the lungs in the OV-treated animals revealed a severe generalised bronchoconstriction and a hyperemia in connection with a slight interstitial edema in all five animals. The rSP-C/PL-treated animals, which were sacrificed after 3 days, showed no bronchoconstriction but a slight increase in the severity of bronchus-associated infiltration with eosinophilic granulocytes and in the formation of peripheral emphysema, but with no dose-dependency. A slight dose-dependent increase in the deposition of peribronchiolar eosinophilic foreign material was evident. In contrast to this, the number of lipid-laden alveolar macrophages seemed to decrease with increasing doses of rSP-C/PL. The immunohistological investigation with a polyclonal antibody against rSP-C showed an intraalveolar distribution of the intratracheally applied rSP-C which is mainly located in the peribronchiolar alveolar parenchyma. A rSP-C-positive staining was visible within the cytoplasm of alveolar histiocytes, type II pneumocytes and also as an extracellularly rim along the alveolar walls. The polyclonal antibody showed no cross reaction with natural occuring SP-C-protein of the guinea pigs. We conclude that the intratracheal application of the rSP-C surfactant containing phospholipids (PL) exhibits no significant risk of an anaphylactic shock reaction in this guinea pig lung hypersensitivity model. The immunohistological investigation with polyclonal antibodies against rSP-C demonstrated clearly the distribution of intratracheal applied material in this toxicological animal model.

Calcium-dependent immunoglobulin E recognition of the apo- and calcium-bound form of a cross-reactive two EF-hand timothy grass pollen allergen, Phl p 7

Type I allergy, an immunodisorder that affects almost 20% of the population worldwide, is based on the immunoglobulin E (IgE) recognition of per se innocuous antigens (allergens). Pollen from wind-pollinated plants belong to the most potent allergen sources. We report the isolation of a cDNA coding for a 8.6 kDa two EF-hand calcium binding allergen, Phl p 7, from a timothy grass (Phleum pratense) pollen expression cDNA library, using serum IgE from a grass pollen allergic patient. Sequence analysis identified Phl p 7 as a member of a recently discovered subfamily of pollen-specific calcium binding proteins. Recombinant Phl p 7 was expressed in Escherichia coli and purified to homogeneity as determined by mass spectroscopy. Approximately 10% of pollen allergic patients displayed IgE reactivity to rPhl p 7 and Phl p 7-homologous allergens present in pollens of monocotyledonic and dicotyledonic plants. Circular dichroism analysis of the calcium-bound and apo-rPhl p 7 indicated that differences in IgE recognition may be due to calcium-induced changes in the protein conformation. The fact that patients mount IgE antibodies against different protein conformations is interpreted as a footprint of a preferential sensitization against either form. The biological activity of rPhl p 7 was demonstrated by its ability to induce basophil histamine release and immediate type skin reactions in sensitized individuals. In conclusion, IgE binding to Phl p 7 represents an example for the conformation-dependent IgE recognition of an allergen. Recombinant Phl p 7 may be used for diagnosis and perhaps treatment of a group of patients who suffer from allergy to pollens of many unrelated plant species.

The extracellular domain of the zeta-chain is essential for TCR function

The zeta-chain homodimer is a key component in the TCR complex and exerts its function through its cytoplasmic immunoreceptor-tyrosine activation motif (1). The zeta-chain extracellular (EC) domain is highly conserved; however, its functional and structural contributions to the TCR signaling have not been elucidated. We show that the EC domain of the zeta homodimer is essential for TCR surface expression. To gain a more detailed structural and functional information about the zeta-chain EC domain, we applied a cysteine scanning mutagenesis to conserved amino acids of the short domain. The results showed that the interchain disulfide bridge can be displaced by seven or eight amino acids along the EC domain. The TCR signaling efficacy was dramatically reduced during peptide/MHC engagement in the zeta mutants containing the displaced disulfide bond. These signaling defective zeta mutants produced an unconventional early tyrosine phosphorylation pattern. While the tyrosine phosphorylated forms of zeta (p21 and p23) could be observed during Ag stimulation, downstream signaling events such as the generation of phospho-p36, higher m.w. forms of phospho-zeta, and phospho-zeta/ZAP-70 complexes were impaired. Together these results suggest an important function of the phylogenetically conserved zeta-EC domain.

Magnetic resonance imaging of PLP-induced experimental allergic encephalomyelitis in Lewis rats

An in vivo magnetic resonance (MR) imaging study was performed on experimental allergic encephalomyelitis (EAE) induced in Lewis rats through proteolipid protein (PLP). PLP was solubilized in water or in an aqueous solution of 1% 10-tridecyl ether (TDE), a non-ionic detergent used in membrane protein research. All 16 rats immunized with 500 microg of TDE-solubilized PLP developed clinical signs and MR abnormalities fully comparable to those observed in MBP-induced EAE. Total paraplegia was observed in 12.5% of rats, mild or moderate paraparesis in 68.8% of rats and tail paralysis in the remaining 18.7% of rats. Whereas only 37.5% of the eight rats immunized with 500 microg of water-solubilized PLP developed minor clinical signs (tail weakness or paralysis). Our observations confirm that the difficulties encountered when trying to induce EAE by means of PLP arise from the highly hydrophobic nature of this protein. Accordingly, if a reproducible model is to be developed, it seems more judicious to use non-ionic detergents in both the extraction and solubilization phases of PLP preparation, this would allow maximal solubilization of the protein while avoiding aggregates, which may otherwise form during either of the PLP preparation.

Influence of some factors on immunoassays of human myoglobin

Six ELISA variants exploiting two monoclonal antibodies, one rabbit antibody and their peroxidase conjugates were applied in assays of purified human myoglobin, apomyoglobin and the protein in human muscle extracts. The myoglobin was accurately determined with monoclonal antibody no. 82 used for coating of ELISA plates while assays performed with monoclonal antibody no. 49 or rabbit antibody used for coating were weak or none. Determinations of human apomyoglobin with ELISA variants were somewhat more sensitive than those of myoglobin. Obtained in this work results were compared with those done using commercial Seratec kit for immunoassay of human myoglobin. Addition to the muscle extracts not only concentrated salts but also acetone, ethanol, sodium dodecyl sulfate or some other denaturing agents markedly increased assays of myoglobin by ELISA with monoclonal antibody no. 49 and antibody no. 82 conjugated with peroxidase. Removal of acetone or ammonium sulfate from extracts resulted in dramatic decrease of the estimated myoglobin. Filtration of the extract through Bio-Gel A5m column did not affect low assays of myoglobin in fractions without pretreatment with acetone. Myoglobin was isolated from human heart extract by immunoaffinity chromatography on Sepharose-antibody no. 82 column and the isolated protein was identified by gel electrophoresis and Western blot.

Coordination of phytochrome levels in phyB mutants of Arabidopsis as revealed by apoprotein-specific monoclonal antibodies

Accumulating evidence indicates that individual members of the phytochrome family of photoreceptors have differential but interactive roles in controlling plant responses to light. To investigate possible cross-regulation of these receptors, we have identified monoclonal antibodies that specifically detect each of the five Arabidopsis phytochromes, phyA to phyE (phytochrome A holoprotein; PHYA, phytochrome A apoprotein; PHYA, phytochrome A gene; phyA, mutant allele of phytochrome A gene), on immunoblots and have used them to analyze the effects of phyA and phyB null mutations on the levels of all five family members. In phyB mutants, but not in phyA mutants, a four- to six-fold reduction in the level of phyC is observed in tissues grown either in the dark or in the light. Coordinate expression of phyB and phyC is induced in the phyB mutant background by the presence of a complementing PHYB transgene. However, in transgenic lines that overexpress phyB 15- to 20-fold, phyC is not similarly overexpressed. In these overexpressor lines, the levels of phyA, phyC, and phyD are increased two- to four-fold over normal in light-grown but not dark-grown seedlings. These observations indicate that molecular mechanisms for coordination or cross-regulation of phytochrome levels are active in Arabidopsis and have implications for the interpretation of phytochrome mutants and overexpressor lines.

APF/CBP, the small, amphipathic, anionic protein(s) in bile and gallstones, consists of lipid-binding and calcium-binding forms

Two very similar small anionic, amphipathic proteins, a phospholipid-binding apoprotein (anionic polypeptide fraction [APF]) and a calcium-binding polypeptide (CBP), are found abundantly in bile and all types of gallstones. The often disparate properties among various preparations of APF/CBP could reflect different sources and separation procedures, leading to partly degraded and/or denatured protein and varied association of bile salts, lipids, bile pigments, and detergents. The present study presents new methods for isolation and purification of APF/CBP, and characterizes the preparations thus obtained. It was found that isolation by selective precipitation of proteins from fresh T-tube bile by added calcium chloride, followed by demineralization with ethylenediaminetetraacetic acid (EDTA), removal of salts, lipids, and some pigment by Sephadex LH-20, and serial ultrafiltration yields the purest preparations. Though free of lipids, bile salts, detergents, and most pigments, these new preparations all show the same 7-kd and 12-kd bands on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), the same major peaks on hydrophobic high-performance liquid chromatography (HPLC), and retain the self-associative, lipid- and calcium-binding functions, typical of older preparations obtained by potentially denaturative procedures. The varied properties among APF/CBP preparations are thus apparently related mainly to their content of different proportions of two major components, lipid-binding APF and calcium-binding CBP. Immunologic cross-reactions indicate common epitopes, and amino acid analyses are also similar, suggesting that APF and CBP may have the same polypeptide backbone, but differ because of posttranslational modification(s). Sufficiently pure APF and CBP have now been obtained to permit possible structural identification by sequencing and molecular biological techniques, though such attempts have thus far been unsuccessful.

Diversity and plasticity of self recognition during the development of multiple sclerosis

Recent studies using murine animal model systems indicate that clinical progression of autoimmune disease may be due to the sequential accumulation of neoautoreactivity characterized by extensive plasticity of self recognition. In the present study, we addressed the question of whether a similar paradigm of self recognition is implicated in the development of multiple sclerosis (MS), a demyelinating disease with a presumed autoimmune etiology. Our approach was to determine serial changes over a 12-18-mo period in response to an epitope-mapping series of 265 12-mer peptides of myelin proteolipid protein (PLP) by patients with isolated monosymptomatic demyelinating syndromes (IMDS), a group of distinct clinical disorders with variable rates of progression to MS. Our data showed that an extensive array of proteolipid protein peptides could elicit autoreactivity. Moreover, differential autoreactive patterns were evident within IMDS patient subpopulations. Monocentric monophasic IMDS patients with no evidence of prior subclinical disease typically showed fully sustained autoreactivity characterized by extensive plasticity, epitope focusing, shifting, and spreading of responses to new self determinants. In contrast, multicentric monophasic IMDS patients with putative evidence of prior asymptomatic lesion formation typically showed partially sustained autoreactivity characterized by abrupt abrogation of responses to an extensive array of self determinants. No sustained autoreactivity was observed in normal control subjects or in patients with other neurologic diseases. Our results indicate that self recognition associated with the development of MS is a developmental process characterized by autoreactive diversity, plasticity, and instability.

Identification of an epitope derived from human proteolipid protein that can induce autoreactive CD8+ cytotoxic T lymphocytes restricted by HLA-A3: evidence for cross-reactivity with an environmental microorganism

The demyelination process that occurs in the central nervous system (CNS) of patients with multiple sclerosis (MS) is in part due to an inflammatory response in which CD4+ and CD8+ T cells and macrophages infiltrate white matter. In this study, we have identified a peptide sequence derived from the CNS-specific myelin protein proteolipid protein (PLP) which could bind to HLA-A3 and induce a HLA-A3-restricted CD8+ CTL response from HLA-A3+ donors. These PLP peptide-specific CTL could lyse HLA-A3+ target cells pulsed with a homologous peptide derived from the CRM1 protein of Saccharomyces cerevisae. These findings demonstrate the immunogenic potential of a PLP-derived peptide for generation of autoreactive HLA-A3-restricted CD8+ CTL, and further show that these CTL can be activated by a peptide derived from a common environmental microorganism.

Monoclonal antibody O10 defines a conformationally sensitive cell-surface epitope of proteolipid protein (PLP): evidence that PLP misfolding underlies dysmyelination in mutant mice

Mutations in the gene for proteolipid protein (PLP) have been associated with CNS dysmyelination and abnormal oligodendrocyte death in spontaneous mouse mutants and in Pelizaeus-Merzbacher disease; however, the effect of mutations on PLP structure and function are little understood. We have identified a monoclonal antibody directed against a novel cell surface epitope of PLP, termed O10. By immunofluorescence analysis, COS-7 cells transiently transfected to express PLP (or its isoform DM20) can be stained with antibody O10 and another antibody (A431) directed against the C terminus of PLP/DM20. The subcellular distribution of immunofluorescence labels for the two antibodies is not identical, suggesting that the O10 epitope is acquired post-translationally. When PLP/DM20 from jimpy, jimpymsd, and rumpshaker mutant mice is expressed in COS-7 cells and compared with wild-type PLP/DM20, none of the mutant isoforms displays the O10 epitope, whereas the C-terminal epitope is detected. Because the O10 but not the A431 epitope is also sensitive to SDS and reducing agents, this strongly suggests abnormal protein folding in the PLP mutants. PLP from jimpymsd mice is obviously misfolded, because the amino acid substitution (Ala242 --> Val) is located within a transmembrane domain to which the O10 antibody does not bind. We propose that the O10 epitope emerges as the full length protein reaches a functional tertiary structure and that the absence of this epitope marks a structural defect of PLP that leads to dysmyelination.

Characterization of monoclonal antibodies to epitopes of human transcobalamin II

Cellular uptake of cobalamin (Cbl) is mediated by transcobalamin II (TCII), a Cbl binding protein in the plasma. The TCII-Cbl complex binds to a cell surface receptor and is internalized by endocytosis. We have generated monoclonal antibodies (mAbs) to human TCII that can be distinguished into three functional types on the basis of interaction with three different regions of the protein. Type 1: Receptor blocking. This mAb binds holo-TCII and inhibits the cellular uptake of Cbl. Type 2: Cbl blocking. This mAb binds apo-TCII at or near the Cbl binding domain and inhibits the formation of holo-TCII. Type 3: Precipitating. This mAb binds both holo-TCII and apo-TCII but does not interfere with Cbl binding. Whereas type 1 and type 2 mAb, following incubation with TCII-[57Co]Cbl or apo-TCII, respectively, inhibit the uptake of radio-labeled Cbl by K562 cells, type 3 mAb has no such activity with either form of TCII. These properties of type 1 and type 2 mAb that inhibit the cellular uptake of Cbl, may serve to induce rapid Cbl deficiency and provide a model to study the effect of selective Cbl depletion on cell division and differentiation as well as on the pathways dependent on the two Cbl cofactors, methyl-Cbl and 5'-deoxyadenosyl-Cbl.

Antigen-specific TGF-beta1 secretion with bovine myelin oral tolerization in multiple sclerosis

Multiple sclerosis is a presumed autoimmune disease, associated with inflammation in the CNS white matter, mediated by autoreactive T cells. We previously reported that oral myelin tolerization of relapsing-remitting MS patients resulted in fewer attacks, as compared to a placebo-fed group. Here, we examined whether oral tolerization with bovine myelin resulted in altered autoreactive T-cell populations or altered T-cell fraction. We generated 4,620 T-cell lines from 34 relapsing-remitting MS patients (17 were fed bovine myelin daily), and each line was examined for proliferation to MBP, PLP, and TT and for secretion of IL-4, IFN-gamma, and TGF-beta1. The frequency of TGF-beta1-secreting T-cell lines after MBP and PLP stimulation in fed patients was greater than that of nonfed patients. These experiments demonstrate that oral tolerization with autoantigen results in altered cytokine secretion in a human autoimmune disease with the generation of TGF-beta1-secreting T cells that may regulate the inflammatory response at the site of the demyelinating lesions in multiple sclerosis. These data provide the first evidence of antigen-specific modification of cytokine secretion in a human autoimmune disease.

Chlamyrhodopsin represents a new type of sensory photoreceptor

In order to find optimal light conditions for photosynthetic growth, the green alga Chlamydomonas uses a visual system. An optical device, a rhodopsin photoreceptor and an electrical signal transduction chain that mediates between photoreceptor and flagella comprise this system. Here we present an improved strategy for the preparation of eyespot membranes. These membranes contain a retinal binding protein, which has been proposed to be the apoprotein of the phototaxis receptor. The retinal binding protein, which we named chlamyopsin, was purified and opsin-specific antibodies were raised. Using these antibodies, the opsin was localized in the eyespot region of whole cells during growth and cell division. The opsin cDNA was purified and sequenced. The sequence reveals that chlamyopsin is not a typical seven helix receptor. It shows some homology to invertebrate opsins but not to opsins from halobacteria. It contains many polar and charged residues and might function as a light-gated ion channel complex. It is likely that this lower plant rhodopsin diverged from animal opsins early in opsin evolution.

Three glycosylated polypeptides secreted by several embryogenic cell cultures of pine show highly specific serological affinity to antibodies directed against the wheat germin apoprotein monomer

Embryogenic tissues of Pinus caribaea Morelet var hondurensis produce extracellular proteins; among them germins have been identified. Two-dimensional electrophoresis followed by electroblotting onto a polyvinylidene difluoride membrane allowed isolation and N-terminal amino acid sequencing of extracellular GP111, which is present within the five embryogenic cell lines studied. The amino acid sequence showed strong homologies with the sequences of germins deduced from cDNA sequencing, starting at the same amino acid position but one, compared with other sequences of mature germins deduced from protein sequencing. Immunoblots of embryogenic and nonembryogenic extracellular proteins indicated that the polypeptide GP111 plus two others with similar relative molecular mass values are present in embryogenic cell lines but not in nonembryogenic ones. They were recognized by an antiserum raised against the nonglycosylated monomer of wheat germin. The cross-reaction between pine and wheat apoproteins was highly specific. An antiserum against the glycosylated pentameric germin-like protein (an oxalate oxidase) of barley cross-reacted with all three, as well as with several other glycosylated polypeptides.

Sequence 104-117 of myelin proteolipid protein is a cryptic encephalitogenic T cell determinant for SJL/J mice

Immunization of animals with myelin proteolipid protein (PLP) causes experimental autoimmune encephalomyelitis (EAE), a disease model that shares many features with human multiple sclerosis (MS). The SJL/J (H-2s) mouse is widely used in EAE studies because of its high disease susceptibility. Previous studies have shown that sequences 139-151 HCLGKWLGHPDKF and 178-191 NTWTTCQSIAFPSK represent distinct co-immunodominant encephalitogenic determinants of PLP for SJL/J mice. In the present study, we identify a third distinct PLP encephalitogenic peptide for SJL/J mice. Following immunization with PLP 104-117 KTTICGKGLSATVT, 10/14 SJL/J mice developed clinical and histological EAE with a mean time of onset of 38 days (18-65 days). T cell lines generated from SJL/J mice immunized with p104-117 were predominantly (> 90%) CD3+, CD4+, alpha beta TCR+, CD8dim, gamma delta TCRdim T cells and responded in an Ag-specific, I-A(s)-restricted manner to p104-117. Upon adoptive transfer of 16-40 x 10(6) T line cells, EAE was produced in naive SJL/J recipients 20-34 days after transfer. The delayed onset of both active and passive disease may be related to the non-immunodominant, cryptic nature of p104-117 in SJL/J mice. Lymph node cells from SJL/J mice immunized with either whole PLP or with pooled encephalitogenic PLP peptides responded to challenge with the immunodominant PLP determinants p139-151 and p178-191 but did not respond to p104-117. The existence of three distinct PLP encephalitogenic T cell determinants for SJL/J mice suggests that susceptibility to EAE and perhaps MS may be related to promiscuous T cell recognition of multiple myelin protein determinants.

Identification of an N-terminally acetylated encephalitogenic epitope in myelin proteolipid apoprotein for the Lewis rat

Proteolipid apoprotein (PLP) is a major component of the central nervous system myelin. As such, it is capable of inducing experimental allergic encephalomyelitis (EAE) in many subhuman species. On the basis of a putative MHC class II binding motif in Lewis rats (RT-1B1) recently identified in our laboratory, the present study identifies one pathogenic T cell epitope of PLP for the Lewis rat, located in the area between amino acid residues 217 and 240. Four overlapping synthetic peptides derived from this region were tested for their antigenicity and encephalitogenicity. Although the longer peptides could not induce EAE in the Lewis rats in their "theoretically" native form after immunization, they were endowed with encephalitogenic ability when modified by N-terminal acetylation. All animals immunized with N-acetylated peptides PLP 217-233 and PLP 224-240 developed inflammation in the lower spinal cord, but with very low incidence of clinical EAE (1 of 12). In contrast, none of the animals immunized with nonacetylated peptides developed either clinical or histologic EAE. Mild inflammation of the spinal cord was also found in two of four rats immunized with N-acetylated peptide PLP 220-234. The animals immunized with the decapeptide, N-acetylated PLP 224-233, did not develop inflammation of the spinal cord. Despite the low incidence of clinical disease, it was possible to generate vigorous T cell lines against all the peptides synthesized from this region of PLP.(ABSTRACT TRUNCATED AT 250 WORDS)

Monoclonal antibody raised against apoprotein of C-1027: effect on biochemical and biological activities of the holoantibiotic

A monoclonal antibody raised against C-1027 apoprotein recognized not only the apoprotein, but also the holoantibiotic (Antibiotic C-1027) almost equally. Among the biochemical and biological activities of the holoantibiotic, the antibody inhibited the aminopeptidase activity and the cytotoxicity to Ehrlich carcinoma cells in cultures, but not the DNA-cleaving activity in vitro. The immunohistogram, using this antibody, of Ehrlich carcinoma cells that had been exposed to the holoantibiotic suggested penetration of the holoantibiotic into target cells.

Cloning and nucleotide sequence of a cDNA encoding a major fucoxanthin-, chlorophyll a/c-containing protein from the chrysophyte Isochrysis galbana: implications for evolution of the cab gene family

We investigated the primary structure of a cDNA encoding a light-harvesting protein from the marine chrysophyte Isochrysis galbana. Antibodies raised against the major fucoxanthin, chlorophyll a/c-binding light-harvesting protein (FCP) of I. galbana were used to select a cDNA clone encoding one of the FCP apoproteins. The nucleic acid and deduced amino acid sequences reveal conserved regions within the first and third transmembrane spans with Chl a/b-binding proteins and with FCPs of another chromophyte. However, the amino acid identity between I. galbana FCP and other cab genes of FCPs is only ca. 30%. Phylogenetic analyses demonstrated that the FCP genes of both diatoms and chrysophytes sequenced to date are more closely related to cab genes encoding LHC I, CP 29, and CP 24 of higher plants than to cab genes encoding LHC II of chlorophytes. We propose that LHC I, CP 24 and CP 29 and FCP might have originated from a common ancestral chl binding protein and that the major LHC II of Chl a/b-containing organisms arose after the divergence between the chromophytes and the chlorophytes.

Protein A antibody-capture ELISA (PACE): an ELISA format to avoid denaturation of surface-adsorbed antigens

Adsorption to a polymeric surface may severely alter the antigenic structure of proteins through unfolding. A conventional capture ELISA in which a protein antigen is adsorbed to the microtiter plate may be unsuitable for testing the specificity of antibodies directed against native proteins (C. Schwab and H.R. Bosshard (1992) J. Immunol. Methods 147, 125). This problem can be overcome by PACE, a new ELISA procedure in which monoclonal or polyclonal antibodies are first allowed to equilibrate with biotinylated antigen in solution. Thereafter, the antigen-antibody complex (and free antibody) is bound to the microtiter plate through protein A. Captured antigen-antibody complex is detected by streptavidin-alkaline phosphatase and p-nitrophenylphosphate. A competition assay is accomplished by co-incubation of biotinylated and non-biotinylated antigens before capture to the protein A-coated plate. PACE combines the advantages of a solution-phase immunoassay (Farr assay) with the ease of a solid-phase ELISA. PACE has been used to test the conformational specificity of polyclonal and monoclonal antibodies against native and denatured cytochrome c, and of a polyclonal antiserum against a coiled coil leucine zipper peptide. Since a biotin group can be attached specifically to the N-terminal residue of synthetic peptides, PACE is also useful for assaying reactivity against peptide antigens which are difficult to adsorb to microtiter plates.

Mapping antibody binding sites on cytochrome c with synthetic peptides: are results representative of the antigenic structure of proteins?

Crystallographic work on antigen-antibody complexes has revealed that extensive surface areas of proteins may interact with antibodies. On the other hand, most experimental approaches to locate and define antigenic determinants of protein antigens rely on the linear sequence of the polypeptide chain. Hence the question arises whether mapping of antibody binding sites by analysis of the reactivity of anti-protein antibodies with synthetic peptides can provide a representative picture of the antigenic structure of a protein antigen. We have addressed this question using yeast iso-1 cytochrome c as a protein antigen against which antisera were raised in rabbits. The reaction of the antisera with 103 synthetic hexapeptides covering the entire sequence of cytochrome c was tested by the pepscan procedure in which peptides are coupled to polyethylene rods and tested by ELISA. For the assay, anti-cytochrome c antibodies were fractionated by affinity chromatography on native yeast iso-1 cytochrome c and on apo-cytochrome c; the latter is a random coil. It was found that only antibodies retained by the apo-cytochrome c affinity column react with synthetic peptides. These antibodies comprise a small fraction, probably less than 2%, of all cytochrome c-specific antibodies. The majority of antigenic determinants, which seem to consist of strongly conformation-dependent topographic epitopes, could not be uncovered by the peptide approach. Epitope mapping with short peptides seems of limited usefulness in the case of small, globular, and conformationally stable proteins like cytochrome c.

Total synthesis of horse heart cytochrome c. Preparation and characterization of the (1-66)apofragment

A peptide corresponding to the native (1-66) sequence of horse heart cytochrome c has been synthesized by stepwise automated solid-phase methods on PAM resin. The course of the synthesis has been monitored by several analytical methods including quantitative ninhydrin and Edman degradation. After HF cleavage, the peptide has been purified by a combination of semipreparative ion-exchange and RP-HPLC. The homogeneity of the purified synthetic peptide has been determined by different criteria including HPLC, amino-acid composition, electrophoresis, antibody binding, tryptic and chymotryptic peptide mapping. After deprotection of the Acm-Cys residues and CNBr cleavage of the Met65-Glu66 peptide bond with simultaneous transformation of the Met65 residue into the activated C-terminal [Hse65]lactone, this purified synthetic peptide has been utilized for conformation-assisted joining experiments in combination with synthetic (66-104) to produce fully synthetic [Hse65]apocytochrome c. This latter, after mitochondria-mediated stereospecific heme insertion, has given a functional molecule corresponding to native horse heart holocytochrome c.

[The immunochemical detection of apoprotein dissociation from particles of very low-density lipoproteins in human blood plasma]

The dissociation of very-low-density lipoprotein (VLDL) apoproteins was studied using immunochemical approaches. The analysis of monospecific antibody binding to apo E, C-II and C-III on VLDL surface showed low apoprotein accessibility for the antibodies while the accessibility of apo C-II and C-III in solution was complete. Lipoprotein preparation dilution resulted in increasing of apo E and C-II accessibility. It was suggested that apoprotein dissociation led to apoprotein cluster dissolving on VLDL surface and higher antigen determinant accessibility. The findings confirmed previous theoretical analysis of apoprotein dissociation.

Determination of fetal age by immunohistochemical estimation of surfactant-producing alveolar type II cells

We monitored the immunohistochemically determined amount of surfactant-producing alveolar type II cells in human fetal lung using polyclonal antibodies against apoprotein B and C of human pulmonary surfactant. Lungs of 30 dead-born fetuses without lung affection aged between 15 and 38 weeks of gestation were evaluated and the surface density of surfactant-producing alveolar type II cells was determined by morphometry. In lungs of fetuses with a gestational age less than 22 weeks no relevant number of positively reacting cells could be found. Between the 22nd and 29th week a progressive increase with considerable inter-individual variability was observed. From the 30th week on the number of the type II pneumocytes appeared rather constant without further significant increase. We provide evidence that the immunohistochemical detection of surfactant-producing alveolar type II cells is useful for the determination of the age of unknown and especially fragmented fetuses: The lack of surfactant-producing alveolar type II cells in fetal lungs before the 22nd week allows a rather safe distinction between fetal lungs of higher age from those of lesser age. Between the 22nd and 29th week an age-dependent increase in the number of these cells occurs with wide inter-individual variability allowing only an approximate age determination. In particular, this may be an important piece of information in fragmented fetal corpses. Furthermore, the number of surfactant-producing alveolar type II cells provides additional information on pulmonary maturation and may thus be helpful in the estimation of a theoretical survival chance.

Identification of type 1 and type 2 light-harvesting chlorophyll a/b-binding proteins using monospecific antibodies

The amino acid sequences of more than 40 apoproteins of the light-harvesting complex associated with Photosystem II (LHC II) of various plants have been deduced by sequencing their corresponding genes. These highly conserved sequences fall into two major categories, type 1 and type 2, that differ mainly in a small number of domains close to the N-terminus. We have made polyclonal, monospecific antibodies against synthetic peptides corresponding to the most unique sequence domains of the N-terminal regions of type 1 and type 2 LHC II apoproteins, using sequences derived from petunia genes. On Western blots our anti-type 1 and 2 antibodies crossreact with light-harvesting proteins of petunia, tomato, spinach and several other plants. By using a new gel-system based on ammediol (2-amino-2-methyl-1,3-propanediol), we are able to resolve up to eight LHC II apoproteins. On petunia, tomato and spinach blots the anti type 1 antibodies bind to two or more of the higher molecular weight LHC II polypeptides, whereas the anti type 2 antibodies recognize very specifically only one or two of the lower molecular weight LHC-proteins. In all plants studied, the type 1 LHC II apoproteins are more numerous and span a greater size range than the type 2 apoproteins. This is consistent with the smaller number of type 2 LHC II CAB genes that have been discovered to date.

Serum IgA antibodies to apoproteins and milk-proteins in severe atherosclerosis

Total serum IgA and IgA antibodies to some milk antigens are often associated with severe atherosclerosis. In the present study we examined the same serum samples to evaluate the possible involvement of serum IgA antibodies to apoproteins and lipoproteins and their relationship to IgA antibodies to milk antigens. We studied 23 subjects with angiographically assessed atherosclerotic lesions (ATS group) and 20 healthy control subjects with a similar age range (59-69 years) and sex distribution. Anti-ApoB, Apo A-I, Apo A-II and anti-LDL, VLDL and HDL antibodies were measured with the ELISA method. All antibodies tested except those to anti-Apo A-I were significantly higher in the ATS group with respect to controls with a maximum significance for anti-Apo B IgA (p = 0.0018). When, for each antibody, a threshold of positivity was set to the mean + 2 SD of values in the control group, 12 ATS subjects (52%) and 1 control (5%) were found to be positive for either anti-Apo B or anti-Apo A-II IgA. Most of the correlations of anti-apoprotein and anti-lipoprotein IgA with anti-milk protein IgA and total IgA were significant. The association of these antibodies with atherosclerosis might either be specific or represent part of a polyclonal IgA response. Whether this association is a cause or an effect of atherosclerotic disease is presently unknown.

[Immunohistochemical study of lung cancer using monoclonal antibody against human pulmonary surfactant apoprotein]

To evaluate the clinical significance of monoclonal antibody against human pulmonary surfactant apoprotein (S-AP), surgically resected lung cancer from 122 patients was studied. Paraffin embedded tissues were used for the immunohistochemical study by the avidin-biotin-peroxidase complex method. The results were as follows. 1. Adenocarcinoma showed highest immunoreactivity for S-AP compared to the other histologic types. Among subtypes of adenocarcinoma, type II alveolar epithelial type, clara cell type and mixed type of these two types were strongly positive (100%, 77.8% and 66.7% respectively). These results indicate that this antibody may be a good marker for the subtyping of adenocarcinoma. 2. There were some positive cases in other histologic types especially in peripheral type of squamous cell carcinoma. These findings suggest that this antibody was useful for the histological differentiation of lung cancer. 3. As to the immunohistochemical reactivity there was a good correlation between tissue and cytological specimens, which indicate cytological studies may be adequate for this kind of histopathological studies. 4. In our study, there were no patients with S-AP positive carcinomas other than patients with lung cancer. These results indicate that this antibody could be used for the differential diagnosis between primary and secondary lung cancer.

Implication of surfactant apoprotein in otitis media with effusion

A two-site simultaneous immunoassay using monoclonal antibodies against human surfactant apoprotein (SAP) was used to measure SAP in middle ear effusions (MEEs). In 130 MEE samples from children with otitis media with effusion, SAP was detected in 54 samples (SAP-positive cases, 41.5%). In the remainder, the SAP concentration was below the sensitivity of the immunoassay (SAP-negative cases, 58.5%). A significant difference in periods of observation was found between the SAP-positive cases (17.3 +/- 16.8 months) and the SAP-negative cases (26.2 +/- 22.5 months) (p less than .01). The percentage of positive cases was highest in the serous MEE group (81.2%) and decreased in the purulent MEE group (57%), the mucoid MEE group (30%), and the hyperviscous MEE group (13.6%), in that order. In the purulent MEE group and the mucoid MEE group, the period of observation was significantly shorter in the SAP-positive cases (18.3 +/- 20.4 months and 20.2 +/- 19.4 months) than in the SAP-negative cases (35.9 +/- 24.5 months and 25.4 +/- 18.7 months) (p less than .05). These results suggest that SAP is present in the middle ear cleft and may be a good prognostic predictor of otitis media with effusion in children.

Extrinsic activation of human coagulation factors IX and X on the endothelial surface

In previous kinetic studies, the catalytic efficiency of the activation of human coagulation factors IX and X by factor VIIa in the presence of purified tissue factor apoprotein was found to be essentially equal. These activation reactions were now studied on the surface of human umbilical vein endothelial cells. The cells were stimulated with endotoxin to express tissue factor. This tissue factor activity was saturable with factor VIIa and could be inhibited by rabbit antibodies against human tissue factor apoprotein. Only stimulated cells supported factor VIIa activity. No difference in the reactivity of factor VII and VIIa was observed in the presence of factor X, due to rapid feedback activation of factor VII by factor Xa. However, the activation of factor IX by factor VII shows a 10 min lag-phase, which reflects that the activation of factor VII by factor IXa is a less efficient process. The kinetic parameters for the factor VIIa dependent activation of factor IX and factor X on the endothelial surface were: Km 0.09 microM, Vmax 0.13 pmol/min, and Km 0.071 microM, Vmax 0.41 pmol/min, respectively. The same ratio between the Vmax for factor X and factor IX activation was observed as in a cell free system. However, the Km of factor IX was 4-fold higher on the endothelial surface than in the cell free system. Together, these kinetic parameters will favour factor X activation 5-fold over factor IX activation at physiological concentrations of these proteins. The activation of factor X by factor VIIa on the endothelial surface was characterized by a short lag-phase, which was absent in factor IX activation.(ABSTRACT TRUNCATED AT 250 WORDS)

An immunoreactive apoglycoprotein purified from Coccidioides immitis

Deglycosylation of glycoproteins in a lysate of spherules of Coccidioides immitis has permitted purification and partial characterization of a proline-rich pronase-sensitive antigen. Moreover, soluble antigen specifically stimulated lymphocytes from persons with dermal delayed-type hypersensitivity to coccidioidal antigens. When related to reference coccidioidin by tandem two-dimensional immunoelectrophoresis, the antigen fused in the anodal region with a specific reference antigen (antigen 2). It did not show identity with coccidioidal antigens used in conventional serologic assays. Although immunoblots of the purified protein with monospecific rabbit antiserum showed a single antigen at 33 kDa, the parent spherule lysate bound the same antibody in a broad band between 70 and greater than 200 kDa, which could be explained by microheterogeneity of glycosylation. Immunoelectron microscopy using affinity-purified human antibodies localized the antigen to the cell wall and internal septa of spherules. These findings suggest that the apoglycoprotein may be important in human immune responses to coccidioidal infection.

Ontogeny of surfactant apoprotein D, SP-D, in the rat lung

Surfactant protein D (SP-D) is a collagenous surfactant-associated glycoprotein synthesized by alveolar type II cells. Antiserum against rat SP-D was raised in rabbits and an enzyme-linked immunosorbant assay (ELISA) has been developed using anti-rat SP-D IgG. In the present study we examined the developmental profile of SP-D in the rat lung compared with that of surfactant protein A (SP-A). SP-A content in the lungs increased during late gestation and reached its maximum on day 1 of neonate, and then gradually decreased until at least day 5. SP-D content during early gestation was less than 10 ng/mg protein until day 18, but on day 19 there was a 4-fold increase in SP-D (compared to that on day 18). It increased twice between day 21 and the day of birth, when it reached the adult level of 250 ng/mg protein, which is about one fourth that of the adult level of SP-A. Unlike SP-A there seemed to be no decrease in SP-D content after birth. These results demonstrate that SP-D is regulated developmentally as are the other components of surfactant, but the inconsistency in the developmental profiles of SP-A and SP-D suggests that these proteins may play different roles in lung maturation.

Mechanism for diminished tissue factor expression by endothelial cells cultured with heparin binding growth factor-1 and heparin

We have extended our earlier observation that growing primary cultures of human umbilical vein endothelial cells (HUVEC) with heparin binding growth factor 1 (HBGF-1) 20 micrograms/mL and heparin 12 U/mL inhibits expression of tissue factor (TF) activity on HUVC monolayers perturbed with thrombin. TF activity was measured as the ability of monolayers or cell lysates to support FVIIa-catalyzed activation peptide release from 3H-FX. TF antigen in HUVEC extracts was measured in an enzyme-linked immunosorbent assay (ELISA) that uses a double-antibody sandwich technique with rabbit and goat antibodies to human TF. TF-mRNA was measured by Northern blot hybridization with a 32P-TF cDNA probe. Cells growth with HBGF-1/heparin had both decreased surface and total TF activity as compared with HUVEC from the same endothelial cell pool grown without HBGF-1/heparin. Means +/- SD for TF antigen for four primary cultures were 4.4 +/- 0.9 ng/10(6) cells without HBGF-1/heparin and 0.6 +/- 0.3 ng/10(6) cells with HBGF-1/heparin. TF mRNA 4 hours after incubation with thrombin of HUVEC grown without HBGF-1/heparin was about sevenfold higher than TF mRNA of HUVEC grown with HBGF-1/heparin. These data establish that growing primary cultures of HUVEC with HBGF-1/heparin impairs their ability to synthesize TF apoprotein after perturbation. This may be part of a generalized response of endothelial cells to HBGF-1/heparin facilitating migration during angiogenesis.

Effect of thymic hormones on induction of experimental allergic encephalomyelitis in old mice

This study was aimed at restoring decreased T-cell functions and reduced susceptibility to proteolipid apoprotein (PLP) induced-experimental allergic encephalomyelitis (EAE) in old mice with thymic hormones. Thymosin fraction 5 (TF-5) and serum thymic factor (FTS) had no significant in vitro and in vivo effect on proliferative responses to PLP and concanavalin A (Con A), and on EAE induction in young and old mice. These results suggest that decreased T-cell functions cannot be restored by these thymic hormones tested.

T-cell recognition of an immunodominant myelin basic protein epitope in multiple sclerosis

Multiple sclerosis is thought to be an autoimmune disease of the central nervous system mediated by T cells specific for a myelin antigen. Myelin basic protein has been studied as a potential autoantigen in the disease because of its role as an encephalitogen in experimental autoimmune encephalomyelitis and post-viral encephalomyelitis and because of the presence in the blood of multiple sclerosis patients of in vivo-activated T cells reactive to myelin basic protein. Immune involvement in multiple sclerosis has been further suggested by the association with the major histocompatibility complex class II phenotype DR2, DQw1. To define the T-cell specificity toward myelin basic protein, 15,824 short-term T-cell lines were established from multiple sclerosis subjects, subjects with other neurological diseases, and normal controls. Here we report a higher frequency of T-cell lines reactive with a DR2-associated region of myelin basic protein between residues 84-102 in patients with multiple sclerosis compared with controls. A second region, identified between residues 143-168, was recognized equally in multiple sclerosis patients and controls and was associated with the DRw11 phenotype. These DR2 and DRw11 associations were also observed among T-cell lines generated from family members of a multiple sclerosis patient. The immunodominant 84-102 peptide from myelin basic protein was both DR2- and DQw1-restricted among different T-cell lines. These results raise the possibility that this immunodominant region may be encephalitogenic in some DR2+ individuals.

Conservation of the carboxyl terminal epitope of myelin proteolipid protein in the tetrapods and lobe-finned fish

Immunochemical analysis of the myelin proteolipid protein (PLP) has identified the carboxyl terminal amino acid phenylalanine 276 as the only PLP epitope conserved between the PLP components of rat and lungfish, species representing the phylogenetically most widely separated groups that synthesise typical CNS myelin. Immunoblotting using a rabbit antiserum raised against the carboxyl terminal sequence of rat PLP (residues 257-276) identified this epitope on the PLP components of both tetrapod (rat, chicken, lizard, and frog) and lobe-finned fish (coelacanth and lungfish) CNS myelin, including the DM-20 isoform of PLP, which is restricted to rat, chicken, and lizard CNS myelin. The conservation of the carboxyl terminus of PLP during evolution suggests this structure may play an important role in maintaining the organisation and function of PLP in the myelin membrane.

Susceptibility to proteolipid apoprotein and its encephalitogenic determinants in mice

We investigated in mice strain differences in induction of experimental allergic encephalomyelitis by proteolipid apoprotein and studied encephalitogenic determinants. SJL/J, C3H/He, CBA/J and A/J mice were high responders, BALB/c and AKR/J mice were moderately susceptible, and DBA/2, B6 and congenic strains of B10 background were low responders. Synthetic peptide 136-150 was encephalitogenic for SJL/J mice, and 215-232 was encephalitogenic for C3H/He mice. These encephalitogenic derterminants are present in the extracellular portion of proteolipid apoprotein in myelin.

Epitope mapping of the monoclonal antibody FAC2 on the apoprotein of Cpa-1 in photosystem II

Using a combination of cyanogen bromide cleavage and endoproteinase digestion we have shown that the putative epitope for the monoclonal antibody FAC2 lies in the region 360Pro(-391)Ser on the apoprotein of CPa-1. This region lies entirely within the large extrinsic loop of this protein. We have shown previously that the epitope of FAC2 becomes exposed in oxygen-evolving membranes upon treatment with alkaline Tris which releases all four of the manganese associated with the oxygen-evolving site of photosystem II. The epitope is not exposed, however, after CaCl(2) treatment and exposure to low concentrations of chloride, conditions which lead to the release of two of the four manganeses associated with the oxygen-evolving site. These results suggest that, upon release of the chloride-insensitive manganese from photosystem II membranes, a conformational change occurs which leads to the exposure of 360Pro(-391)Ser on CPa-1 to the monoclonal antibody FAC2.

Autoantibodies to each protein fraction extracted from cerebral endothelial cell membrane in the sera of patients with multiple sclerosis

Damage to the blood-brain barrier (BBB) occurs in multiple sclerosis (MS), probably due to an immunological mechanism. Anti-endothelial cell antibodies may play a pathogenetic role in the BBB damage. Our previous studies led us to search for which protein fraction extracted from cerebral endothelial cell membrane was reactive to antibodies in the sera of patients with MS. The antibodies to each protein fraction extracted from the rat cerebral endothelial cell membrane were studied in patients with MS, other neurological diseases and controls using an enzyme-linked immunosorbent assay (ELISA) method. The patients with active relapsing MS (P less than 0.01) displayed significantly higher levels of immunoglobulin G (IgG) binding to the endothelial cell membrane fraction than did the controls. The sera of the same patients (P less than 0.001) also showed significantly higher levels of antibodies to fraction I (8.0 kDa) than did the normal controls. The high levels of IgG binding to fraction II (11.0 kDa) and III (12.3 kDa) were significantly increased in the sera of patients with active relapsing MS compared to normal controls (P less than 0.01). The immune response to the protein fraction extracted from the cerebral endothelial cell membrane fraction may indicate a result of the BBB damage in the case of MS.

Antigenicity of low molecular weight surfactant species

The authors tested the antigenicity of human lung surfactant isolated from amniotic fluid. Mice and rabbits were immunized. Rabbit polyclonal antisera to these surfactant preparations were absorbed with normal human plasma proteins. Polyclonal antisera reacted with both high molecular weight (35 kd) surfactant apoprotein and to lower molecular weight species, both 18 kd and 9 kd. Mice were used to generate monoclonal antibodies to surfactant. Enzyme-linked immunosorbant assay was used to identify five monoclonal antibodies that reacted with surfactant. By Western blot analysis, all of these recognized a low molecular weight surfactant species (9 kd) that could be either SP-B or SP-C. One reacted with a 37 kd protein in the surfactant preparation, consistent with SP-A. One monoclonal antibody also recognized a higher molecular weight species (44 kd) of unknown origin. The ability of antisera and monoclonal antibodies to inhibit the functional activity of surfactant was assayed using a pulsating bubble surfactometer. Rabbit polyclonal antisera inhibited initial surface adsorption to equilibrium surface tension and increased the minimum surface tension after 1 and 5 minutes of initiation of pulsations. This inhibitory activity of the antisera was noted in divalent F(ab')2 fragments. Monovalent F(ab) fragments and control normal rabbit sera did not inhibit surfactant function in this assay. Of the anti-surfactant monoclonal antibodies that reacted with surfactant by ELISA and Western blot, three inhibited its capacity to lower surface tension on the pulsating bubble apparatus. The other two monoclonal antibodies showed no functional inhibitory activity. It is concluded that both the 35 kd SP-A and the 9 kd proteins of human surfactant are highly immunogenic and partially crossreactive. Resulting antibodies could alter the ability of surfactant to perform its physiologic function, ie, to lower surface tension.

The adoptive transfer of chronic relapsing experimental allergic encephalomyelitis with lymph node cells sensitized to myelin proteolipid protein

In this report we describe the transfer of chronic relapsing experimental allergic encephalomyelitis (EAE) with in vitro-stimulated lymph node cells (LNC) from SJL/J mice immunized with human myelin proteolipid protein (PLP). No additional immune enhancing procedures were applied in the transfer recipients. Clinical and histological EAE was transferred with 10-30 X 10(6) LNC to 27/28 mice. The LNC proliferated in vitro to PLP, but not to myelin basic protein (MBP), and induced delayed-type hypersensitivity. Enrichment for lymphoblasts by Ficoll centrifugation was essential for the disease development. The clinical course usually showed an early episode of acute paralytic illness, followed by chronic relapsing disease, and resembled the transfer of EAE using MBP-specific cells, both clinically and histologically.

Monoclonal antibody recognizes a conformational epitope in a random coil protein

The antigenic determinants for two monoclonal antibodies directed against horse apo-cytochrome c, a protein of disordered structure, as judged by spectroscopic and hydrodynamic criteria, have been studied by a combination of methods: antigen competition in solution by radio immunoassay and enzyme-linked immunoassay, and differential acetylation of free and antibody-bound antigen. In the latter method the accessibility of lysine residues of the antigen in the antigen-antibody complex is compared to the accessibility in the free antigen. The two antibodies against the heme-free protein do not recognize intact native cytochrome c, but they crossreact with the heme-containing peptides 1-38 and 1-65 of cytochrome c. The antigenic determinant recognized by monoclonal antibody SJL 2-4 is conformational and discontiguous, it is composed of residues close to the N-terminus and around position 25. The other monoclonal antibody, Cyt-1-59, seems to recognize a contiguous epitope close to the N-terminus. The present results show that even a seemingly disordered protein which is conventionally classified as a random coil may feature subtle spatial regularities. The presence of ordered conformational elements in apocytochrome c may be important for the enzyme-catalyzed covalent attachment of the heme and the import of cytochrome c into mitochondria. A discontiguous determinant for SJL 2-4 is particularly interesting because this antibody inhibits the proliferation of a T-cell clone specific for apo-cytochrome c [Corradin & Engers (1984) Nature (Lond.) 308, 547-548].