Chromosomal locations of the murine T-cell receptor alpha-chain gene and the T-cell gamma gene

Becoming aware of γδ T cells

The discovery that B cells and αβ T cells exist was predictable: These cells gave themselves away through their products and biological effects. In contrast, there was no reason to anticipate the existence of γδ T cells. Even the accidental discovery of a novel TCR-like gene (later named γ) that did not encode TCR α or β proteins did not immediately change this. TCR-like γ had no obvious function, and its early expression in the thymus encouraged speculation about a possible role in αβ T cell development. However, the identification of human PBL-derived cell-lines which expressed CD3 in complex with the TCR-like γ protein, but not the αβ TCR, first indicated that a second T cell-type might exist, and the TCR-like γ chain was observed to co-precipitate with another protein. Amid speculation about a possible second TCR, this potential dimeric partner was named δ. To determine if the δ protein was indeed TCR-like, we undertook to sequence it. Meanwhile, a fourth TCR-like gene was discovered and provisionally named x. TCR-like x had revealed itself through genomic rearrangements early in T cell development, and was an attractive candidate for the gene encoding δ. The observation that δ protein sequences matched the predicted amino acid sequences encoded by the x gene, as well as serological cross-reactivity, confirmed that the TCR-like x gene indeed encoded the δ protein. Thus, the γδ heterodimer was established as a second TCR, and the cells that express it (the γδ T cells) consequently represented a third lymphocyte-population with the potential of recognizing diverse antigens. Soon, it became clear that γδ T cells are widely distributed and conserved among the vertebrate species, implying biological importance. Consistently, early functional studies revealed their roles in host resistance to pathogens, tissue repair, immune regulation, metabolism, organ physiology and more. Albeit discovered late, γδ T cells have repeatedly proven to play a distinct and often critical immunological role, and now generate much interest.

Cellular immune responses in the pathophysiology of preeclampsia

Preeclampsia, defined as new-onset hypertension accompanied by proteinuria occurring at 20 weeks of gestation or later, is a leading cause of perinatal morbidity and mortality worldwide. The pathophysiology of this major multi-systemic syndrome includes defective deep placentation, oxidative stress, endothelial dysfunction, the presence of an anti-angiogenic state, and intravascular inflammation, among others. In this review, we provide a comprehensive overview of the cellular immune responses involved in the pathogenesis of preeclampsia. Specifically, we summarize the role of innate and adaptive immune cells in the maternal circulation, reproductive tissues, and at the maternal-fetal interface of women affected by this pregnancy complication. The major cellular subsets involved in the pathogenesis of preeclampsia are regulatory T cells, effector T cells, NK cells, monocytes, macrophages, and neutrophils. We also summarize the literature on those immune cells that have been less characterized in this clinical condition, such as γδ T cells, invariant natural killer T cells, dendritic cells, mast cells, and B cells. Moreover, we discuss in vivo studies utilizing a variety of animal models of preeclampsia to further support the role of immune cells in this disease. Finally, we highlight the existing gaps in knowledge of the immunobiology of preeclampsia that require further investigation. The goal of this review is to promote translational research leading to clinically relevant strategies that can improve adverse perinatal outcomes resulting from the obstetrical syndrome of preeclampsia.

Age-dependent TCR revision mediated by interaction between alphabeta TCR and self-antigens

Interactions between TCR and self-peptide/MHC complex play an important role in homeostasis and Ag reactivity of mature peripheral T cells. In this report, we demonstrate that the interactions between mature peripheral T cells and endogenous Ags have a negative impact on the maintenance of foreign Ag-specific T cells in an age-dependent manner. This is mediated by RAG-dependent secondary rearrangement of the TCR alpha-chain (receptor revision). The TCR revision in mature T cells is readily observed in mouse expressing transgenic TCR alpha-chain inserted into the physiological locus (knockin mouse) but not in conventional transgenic mouse with an identical TCR alpha-chain. Thus, our results suggest that under physiological conditions in which all TCR alpha-chains are susceptible to deletion by secondary rearrangement, TCR revision in mature peripheral T cells is an ongoing process in adult animals and contributes to age-dependent changes in T cell function and repertoire.

Aberrant recombination involving the granzyme locus occurs in Atm-/- T-cell lymphomas

Ataxia telangiectasia (A-T) is an autosomal recessive disease caused by loss of function of the serine/threonine protein kinase ATM (ataxia telangiectasia mutated). A-T patients have a 250-700-fold increased risk of developing lymphomas and leukemias which are typically highly invasive and proliferative. In addition, a subset of adult acute lymphoblastic leukemias and aggressive B-cell chronic lymphocytic leukemias that occur in the general population show loss of heterozygosity for ATM. To define the specific role of ATM in lymphomagenesis, we studied T-cell lymphomas isolated from mice with mutations in ATM and/or p53 using cytogenetic analysis and mRNA transcriptional profiling. The analyses identified genes misregulated as a consequence of the amplifications, deletions and translocation events arising as a result of ATM loss. A specific recurrent disruption of the granzyme gene family locus was identified resulting in an aberrant granzyme B/C fusion product. The combined application of cytogenetic and gene expression approaches identified specific loci and genes that define the pathway of initiation and progression of lymphoreticular malignancies in the absence of ATM.

High frequency of QPY allele and linkage disequilibrium of granzyme-B in Epstein-Barr-virus-associated hemophagocytic lymphohistiocytosis

Mediation of Epstein-Barr virus (EBV)-specific cytotoxicity in T lymphocyte via the perforin/granzyme pathway has been demonstrated; therefore, a study involving cytolytic molecules was essential for the clarification of hemophagocytic lymphohistiocytosis (HLH) pathogenesis. This investigation, which analysed the frequency of three allelic mutations of granzyme-B (55Q/R, 95P/A and 247Y/H) in patients with EBV-HLH and infectious mononucleosis, identified the high prevalence of the QPY haplotype in EBV-HLH patients in comparison with healthy controls. A > G polymorphism was also detected in intron 5; furthermore, nearly complete linkage disequilibrium was observed among these polymorphisms. The recessive role of the QPY haplotype of granzyme-B might be responsible for the pathogenesis of EBV-HLH. Cytotoxicity and DNA fragmentation of cytotoxic T lymphocytes did not differ among patients characterized by the QPY/QPY, RAH/RAH and QPY/RAH genotypes. This finding suggested that DNA fragmentation in target cells is mediated not only by granzyme-B but also by other molecules, including other granzymes or Fas.

T-cell receptor gamma: a microsatellite marker for colorectal cancer

BACKGROUND

T-cell receptor gamma (TCR-gamma) is involved in maintaining host cell integrity and homeostasis of the human immune system. We hypothesize that polymorphism of the TCR-gamma complex may be involved in the pathogenesis of colorectal cancer.

METHODS

The microsatellite markers D7S1818 and D7S2206 located within the TCR-gamma antigen locus on chromosome 7p were amplified by polymerase chain reaction, and genotypes were determined for 22 patients with early onset of colorectal cancer (<60 years old) and for 38 population-based control subjects.

RESULTS

Genotype BC of D7S1818 (P = .049) and haplotype AC of D7S1818/D7S2206 (P < or = .003) were associated with colorectal cancer as compared with the control population (extended Fisher's exact test).

CONCLUSIONS

This study identifies a novel genetic and clinical association between TCR-gamma and early-onset colorectal cancer. Many young patients do not fulfill the criteria for hereditary colorectal cancer syndromes and are therefore not identified by established screening programs. Markers such as D7S1818 and D7S2206 may become useful in the identification of patients at risk of developing colorectal cancer and permit earlier therapeutic intervention.

Somatic cell mapping of T-cell receptor CD3 complex and CD8 genes in cattle

Bovine genes encoding T-cell receptor, CD3, and CD8 molecules have been mapped to syntenic groups using bovine x rodent hybrid somatic cells. T-cell receptor alpha and delta chains were assigned to bovine syntenic group U5, and the beta and gamma genes were syntenic with each other and with markers on U13. CD3E and CD3D genes were syntenic with each other and located to bovine syntenic group U19. CD8 was most concordant with markers of syntenic group U16, although the concordancy was only 85% and the assignment must be regarded as tentative. The comparative gene maps of human chromosome 7, bovine syntenic group U13, and mouse chromosomes 6 and 13 suggest extensive evolutionary conservation.

Down-regulation of a member of the S100 gene family in mammary carcinoma cells and reexpression by azadeoxycytidine treatment

A cDNA clone, designated CaN19 (originally called clone 19), isolated by subtractive hybridization, contains sequences that are preferentially expressed in normal mammary epithelial cells but not in breast tumor cells. Comparison of its deduced amino acid sequence with sequences in the GenBank data base revealed similarity with the S100 protein family, a group of small Ca(2+)-binding modulator proteins involved in cell cycle progression and cell differentiation. CaN19 expression is down-regulated in normal cells by A23187, a calcium ionophore, suggesting that its regulation is calcium-dependent. We have assigned CaN19 to human chromosome 1q21-q24, a region containing four other S100-related genes. In contrast to CaN19 mRNA expression, most members of the S100 protein family are activated or overexpressed in tumor cells. Synchronization experiments by growth-factor deprivation demonstrated a biphasic induction of CaN19 expression in normal cells, approximately 2-fold in early G1 phase and another 2- to 3-fold at the G1/S boundary. Exposure of mammary tumor cells to 5-aza-2'-deoxycytidine, an inhibitor of DNA methylation, reactivated the expression of CaN19 mRNA.

Novel excision products of T cell receptor gamma gene rearrangements and developmental stage specificity implied by the frequency of nucleotide insertions at signal joints

We have cloned circular DNA excised by T cell receptor (TcR) gamma 1, gamma 2 and gamma 3 gene rearrangements in fetal and adult mouse thymocytes. Circular DNA contained a signal joint reciprocal to the genomic V-J coding joint. Although signal joints without nucleotide insertions are common in immunoglobulin (Ig) and TcR gene rearrangements, the signal joint of gamma found in adult thymocytes contained non-germ-line element (N) insertions at high frequency, while no insertions were found in fetal thymocytes. Thus developmental stage specificity of TcR gamma gene rearrangements is faithfully reflected on the signal joint of excision products. In addition, examination of gamma gene excision products revealed circular DNA products of TcR gamma-alpha transrearrangements, but no evidence of V gamma gene replacement in a rearranged segment.

Polymorphisms revealed by PCR with single, short-sized, arbitrary primers are reliable markers for mouse and rat gene mapping

Ten single, arbitrarily designed oligodeoxynucleotide primers, with 50-70% (G+C) content, were used to amplify by polymerase chain reaction (PCR) sequences with DNA templates from several mouse species (Mus spretus, Mus musculus musculus, and Mus musculus domesticus), as well as DNA from the laboratory rat (Rattus norvegicus). Eight of these ten primers, used either individually or associated in pairs, generated a total of 13 polymorphic products which were used as genetic markers. All of these polymorphic sequences but one were mapped to a particular mouse chromosome, by use of DNA panels prepared either from interspecific backcross progeny of the type (C57BL/6 x Mus spretus)F1 x C57BL/6 or DNA samples prepared from two sets of recombinant inbred (RI) strains (AKXL and BXD). Six rat-specific DNA segments were also assigned to a particular chromosome with DNA panels prepared from 18 rat/mouse somatic cell hybrids segregating rat chromosomes. From these experiments we conclude that, under precisely standardized PCR conditions, the DNA molecules amplified with these arbitrarily designed primers are useful and reliable markers for genetic mapping in both mouse and rat.

Greig syndrome associated with an interstitial deletion of 7p: confirmation of the localization of Greig syndrome to 7p13

An 11-month-old infant with Greig cephalopolysyndactyly syndrome and mild developmental delay is described. High-resolution chromosomal analysis showed a de novo interstitial deletion of chromosome 7p with breakpoints located at p13 and p14. Cytogenetic analysis of polymorphisms of the heterochromatin in the pericentromeric region suggested the deleted chromosome was of paternal origin. This case confirms the localization of Greig syndrome to 7p13 and emphasizes the importance of performing cytogenetic studies on patients with Mendelian disorders who have unusual findings or cognitive abnormalities in a disorder usually associated with normal intellect. Review of clinical features in published reports of patients with a deletion involving 7p13 showed a number to have features overlapping with Greig syndrome. Because of this, we suggest that cytogenetic aberrations, particularly chromosomal microdeletions, may represent a significant etiology for Greig syndrome.

Repertoire development and ligand specificity of murine TCR gamma delta cells

During the past several years, we have been studying the circulating TCR gamma delta cells expressed in peripheral lymphoid tissues. Biochemical and molecular characterization of the TCR gamma delta heterodimers present on these TCR gamma delta cells identified 3 TCR gamma proteins, V gamma 2-C gamma 1, V gamma 1.2-C gamma 2, and V gamma 1.1-C gamma 4. In addition, at least 6 different V delta gene products (V delta 2,4,5,6,V alpha 10, V alpha 11) are expressed in peripheral lymphoid tissue. Nucleotide sequence analysis has revealed a great deal of junctional diversity present among the different V gamma and V delta proteins. Thus, compared to other nonlymphoid tissues (e.g., skin), this population of TCR gamma delta cells appears quite extensive. The development and specificity of TCR gamma delta cells has been pursued by two approaches. First, different TCR gamma delta cells clones were generated which recognize MHC-encoded gene products. One clone recognizes an unconventional TL-encoded antigen, whereas others have been shown to recognize either classical MHC class I or class II antigens. The TCR gamma delta receptor genes have been cloned from the TL-specific TCR gamma delta cell and used to construct transgenic mice to examine the development of TCR gamma delta cells. Although the Tg+ TCR gamma delta cells are tolerized by thymic clonal tolerance similar to TCR alpha beta cells, the epithelial Tg+ TCR gamma delta cells are subjected to non-deletional tolerance (anergy). A second approach towards examining the development of TCR gamma delta cells has been to compare the repertoire of TCR gamma delta splenocytes in a variety of inbred and MHC-congenic strains of mice using subset-specific anti-murine TCR gamma delta mAb. The percentage of individual subsets of splenic TCR gamma delta cells differ widely between different inbred strains of mice due to both MHC- and TCR-encoded genetic differences. In summary, these studies provides a basis for understanding and determining the ligand(s) of the TCR gamma delta heterodimer and the factors which shape the peripheral TCR gamma delta repertoire.

T-cell receptor and autoimmune disease

Since the genes encoding the TCR have been cloned, their structure, organization, pattern of rearrangement, diversification and expression in ontogeny have been classified. However, there are still many important questions to be addressed, such as the nature of thymic education, tolerance, the mechanism of MHC-restricted antigen recognition and the relation between TCR repertoire and autoimmunity. In the future, new approaches to study these issues, such as transgenic mice, X-ray crystallography, and severe combined immune deficiency mice reconstituted with human hematopoietic cells will lead to a more profound understanding of these questions. This will hopefully allow us to manipulate the immune response in different and more effective ways than are currently available.

Structural organization of the hCTLA-1 gene encoding human granzyme B

Cytotoxic T lymphocytes (CTLs) and natural killer/lymphokine-activated cells produce granzymes, a family of serine esterase proteins located in cytoplasmic granules. These might be involved in different cytotoxic pathways. We report the structural organization of the human gene encoding granzyme B (hCTLA-1). A 4.75-kb genomic DNA fragment containing all the sequences of granzyme B-encoding cDNA clones has been sequenced. The gene is composed of five exons and four introns. A comparison with the genomic organization of murine CCP1/CTLA-1 showed very similar structure and a 76% nucleotide homology in the coding sequences. This suggests that both genes may have a common ancestor. No typical regulatory element was detected in the 1160 bp upstream from the ATG start codon. The detection of a second locus related to hCTLA-1 is also described.

A complex of serine protease genes expressed preferentially in cytotoxic T-lymphocytes is closely linked to the T-cell receptor alpha- and delta-chain genes on mouse chromosome 14

A complex of genes encoding serine proteases that are preferentially expressed in cytotoxic T-cells was shown to be closely linked to the T-cell receptor alpha- and delta-chain genes on mouse chromosome 14. A striking difference in recombination frequencies among linkage crosses was reported. Two genes, Np-1 and Tcra, which fail to recombine in crosses involving conventional strains of mice, were shown to recombine readily in interspecific crosses involving Mus spretus. This difference in recombination frequency suggests chromosomal rearrangements that suppress recombination in conventional crosses, recombination hot spots in interspecific crosses, or selection against recombinant haplotypes during development of recombinant inbred strains. Finally, a mutation called disorganization, which is located near the serine protease complex, is of considerable interest because it causes an extraordinarily wide variety of congenital defects. Because of the involvement of serine protease loci in several homeotic mutations in Drosophila, disorganization must be considered a candidate for a mutation in a serine protease-encoding gene.

A molecular genetic linkage map of mouse chromosome 13 anchored by the beige (bg) and satin (sa) loci

A molecular genetic linkage map of mouse chromosome 13 was constructed using cloned DNA markers and interspecific backcross mice from two independent crosses. The map locations of Ctla-3, Dhfr, Fim-1, 4/12, Hexb, Hilda, Inhba, Lamb-1.13, Ral, Rrm2-ps3, and Tcrg were determined with respect to the beige (bg) and satin (sa) loci. The map locations of these genes confirm and extend regions of homology between mouse chromosome 13 and human chromosomes 5 and 7, and identify a region of homology between mouse chromosome 13 and human chromosome 6. The molecular genetic linkage map of chromosome 13 provides a framework for establishing linkage relationships between cloned DNA markers and known mouse mutations and for identifying homologous genes in mice and humans that may be involved in disease processes.

Influence of non-major histocompatibility complex differences on the severity of lymphocytic choriomeningitis

The role of the non-major histocompatibility complex (MHC) genetic background in the development of lymphocytic choriomeningitis (LCM) was examined for a range of mouse strains of the H-2k haplotype. The onset of meningitis relative to the time of injection of LCM virus was delayed and the maximal level of cellular extravasation into cerebrospinal fluid was lower in C3H/HeJ and CBA/H compared with AKR/J, B10.Br and BALB/c.H-2k mice. Adoptive transfer experiments indicated that the C3H mice are genuine low responders, but immune spleen cells from the CBA/H were as potent on a cell-for-cell basis as those from the AKR/J. Further analysis with CBA/H, AKR/J and (CBA/H x AKR/J)F1 mice showed that the pattern of high response for the AKR/J was dominant, with the differential kinetics of the development of meningitis correlating with the cellularity of the cervical lymph nodes. Thus, the generation of the LCM inflammatory process is not dictated solely by the MHC phenotype.

Mapping of genes for inhibin subunits alpha, beta A, and beta B on human and mouse chromosomes and studies of jsd mice

Inhibin (INH) is a gonadal glycoprotein hormone that regulates pituitary FSH secretion and may also play a role in the regulation of androgen biosynthesis. There are two forms of inhibin that strongly inhibit pituitary FSH secretion. These share the same alpha subunit that is covalently linked to one of two distinct beta subunits (beta A or beta B). However, dimers of two beta subunits are potent stimulators of FSH synthesis and release in vitro. The beta subunits share extensive sequence similarity with transforming growth factor beta. Recently isolated cDNAs for all three inhibin subunits have been used to map their cognate loci on human and mouse chromosomes by Southern blot analysis of somatic cell hybrid DNAs and by in situ hybridization. INH alpha and INH beta B genes were assigned to human chromosome 2, regions q33----qter and cen----q13, respectively, and to mouse chromosome 1. The INH beta A locus was mapped to human chromosome 7p15----p14 and mouse chromosome 13. The region of mouse chromosome 1 that carries other genes known to have homologs on human chromosome 2q includes the jsd locus (for juvenile spermatogonial depletion). Adult jsd/jsd mice have elevated levels of serum FSH and their testes are devoid of spermatogonial cells. The possibility that the mutation in jsd involves the INH alpha or INH beta B gene was investigated by Southern blotting of DNA from jsd/jsd mice, and no major deletions or rearrangements were detected.

Restriction fragment length polymorphisms of the mouse T-cell receptor gene families

We have studied the restriction fragment length polymorphisms (RFLPs) found in the germline T-cell receptor genes of 25 inbred Mus musculus strains and 8 wild Mus species. Included in the inbred mice tested were several strains which spontaneously develop systemic autoimmune disease. Extensive polymorphism was evident for the variable (V) gene segments of the alpha gene family for both the inbred strains and wild mouse species. Changes in the total number of bands hybridizing with probes for V alpha gene segments suggest that members of a V alpha gene segment subfamily are not closely linked, but are interspersed with members of other subfamilies; that expansion and contraction of the multimembered subfamilies may be an important diversifying factor. Our data obtained with beta gene probes revealed genomic diversity that is much more limited than that seen for the alpha locus. Analysis of inbred mice with probes for the gamma gene locus revealed some RFLPs, but little evidence of expansion or contraction in the numbers of gene segments. Among the autoimmune mice, NZW, NZB, and BXSB/MpJ all display distinctive differences with alpha gene probes. NZW mice have a large deletion of the beta gene family, which has been reported previously. We found no differences to distinguish the MRL/MpJ lpr/lpr mice from non-autoimmune strains.

Proximity of the CTLA-1 serine esterase and Tcr alpha loci in mouse and man

The serine esterase CTLA-1 gene was shown by in situ hybridization to map to the D segment of mouse chromosome 14, the same localization as a member of the immunoglobulin superfamily, Tcr alpha. To further demonstrate the proximity of CTLA-1 and Tcr alpha, genetic linkage was tested in mouse using restriction fragment length polymorphisms and a backcross progeny, and no recombination was observed in the 100 backcross products studied. Recombination events between Tcr alpha/CTLA-1 and the markers Gdh-X and NP-1 show that the most probable order of these loci in the mouse 14D region is NP-1-Tcr alpha/Ctla-1-Gdh-X. In man, the human homologue of CTLA-1 was shown by in situ hybridization to map on chromosome 14, at 14q11-q12, where Tcr alpha also maps. Using the human cell line SUP-T1, bearing the inversion inv(14) (q11;q32), we further demonstrated the loci order in man to be centromere-NP-1-Tcr alpha-CTLA-1. To complement the cytogenetic and genetic mapping data, we tried to determine the physical distance between the two genes by pulsed field gel electrophoresis (PFGE). DNA prepared from various cell types, both mouse and human, were digested with a panel of rare cutter enzymes and hybridized first with CTLA-1, then with Tcr alpha probes. None of the bands identified hybridized with both Tcr alpha and CTLA-1 probes for either mouse or human cells. Although the physical mapping by PFGE is inconclusive, the cytogenetic and genetic data support close linkage of the Tcr alpha and CTLA-1 genes in both mouse and man, suggesting homology between the D region of mouse chromosome 14 and the q11-q12 region of human chromosome 14, encompassing the Tcr alpha and CTLA-1 loci. These findings also provide another example of proximity of genes coding for a member of the Ig super-family and a serine esterase.

Greig cephalopolysyndactyly syndrome: a possible mouse homologue (Xt-extra toes)

Greig cephalopolysyndactyly syndrome is an autosomal dominant form of complex polydactyly in man. Attention is called to the evidence that, on both morphological and comparative gene mapping grounds, this defect is homologous to Xt-extra toes in the mouse. The pattern of polydactyly in both species is very similar. In addition, both conditions probably map close to the T-cell receptor gamma polypeptide at 13 A2-3 in mouse and 7p15 in humans.

Chromosomal localisation of a developmental gene in man: direct DNA analysis demonstrates that Greig cephalopolysyndactyly maps to 7p13

Greig cephalopolysyndactyly syndrome (GCPS) is a rare autosomal dominant form of complex polydactyly. GCPS has been tentatively assigned to chromosome 7 on the basis of association of the condition with balanced translocations involving the short arm of chromosome 7 (7p13) in two families. Seven GCPS pedigrees with no chromosome abnormality were studied, and linkage was demonstrated between GCPS and the DNA sequence coding for the receptor for epidermal growth factor (localised to 7p12-13) (Z = 3.17; O = theta).

Fim-1, Fim-2/c-fms, and Fim-3, three common integration sites of Friend murine leukemia virus in myeloblastic leukemias, map to mouse chromosomes 13, 18, and 3, respectively

Three common proviral integration sites, Fim-1, Fim-2/c-fms, and Fim-3, have been described in mouse myeloid leukemias induced by the Friend murine leukemia virus. The nature and function of Fim-1 and Fim-3 are still unknown since no transcript from these loci has been detected so far. To identify these two loci, we undertook their chromosomal localization using restriction fragment length polymorphism detected between C57BL/6 mice and the wild-derived inbred strain of Mus spretus. Using interspecific backcross analysis, we mapped Fim-1 to mouse chromosome 13 and Fim-3 to mouse chromosome 3. Interestingly, Fim-3 is tightly linked to Evi-1, another common integration site of ecotropic virus involved in another model of mouse myeloid leukemogenesis. Fim-2 spans the 5' end of the c-fms gene, which encodes for the macrophage-colony-stimulating factor receptor. We located the c-fms gene on the D band of chromosome 18 by in situ hybridization.

Murine thymomas induced by fractionated-X-irradiation have specific T-cell receptor rearrangements and characteristics associated with day-15 to -16 fetal thymocytes

We report here that specific T-cell receptor rearrangements were observed in fractionated-X-irradiation-induced murine leukemias. Consistent gamma-chain rearrangements, limited beta-chain rearrangements, and no detectable alpha-chain rearrangements were observed. Gene expression studies revealed that, in comparison with normal thymus tissue, expression of alpha T-cell receptor genes was lower in the thymomas, beta expression was much higher but approximately equal to that of normal thymocytes, and gamma expression was significantly increased. After coupling these data with those from analyses using reagents against other surface markers, such as Lyt-2, L3T4, H-2, IL-2R and MEL-14, we concluded that the target T cells for fractionated-X-irradiation-induced transformation resemble fetal thymocytes from days 15 and 16 of gestation.

Murine thymomas induced by fractionated-X-irradiation have specific T-cell receptor rearrangements and characteristics associated with day-15 to -16 fetal thymocytes

We report here that specific T-cell receptor rearrangements were observed in fractionated-X-irradiation-induced murine leukemias. Consistent gamma-chain rearrangements, limited beta-chain rearrangements, and no detectable alpha-chain rearrangements were observed. Gene expression studies revealed that, in comparison with normal thymus tissue, expression of alpha T-cell receptor genes was lower in the thymomas, beta expression was much higher but approximately equal to that of normal thymocytes, and gamma expression was significantly increased. After coupling these data with those from analyses using reagents against other surface markers, such as Lyt-2, L3T4, H-2, IL-2R and MEL-14, we concluded that the target T cells for fractionated-X-irradiation-induced transformation resemble fetal thymocytes from days 15 and 16 of gestation.

T-cell gamma gene is allelically but not isotypically excluded and is not required in known functional T-cell subsets

The T-cell gamma genes, structurally related to immunoglobulin genes and the T-cell antigen-receptor alpha- and beta-chain genes, undergo somatic rearrangement in T-lineage cells. However, the role of the T-cell gamma genes has not yet been determined. To determine the potential for gamma gene expression in a set of well-characterized, cloned T-cell lines, we cloned all of the rearranged gamma genes from each cell line. The genes were sequenced to determine if the junction of the variable and joining regions maintained the proper translational reading frame. We then attempted to correlate the presence of an in-frame gamma gene with a T-cell subset. We were unable to establish such a correlation. We found evidence, however, that allelic exclusion influences the rearrangement of the gamma gene. This is consistent with the idea that the gamma gene product participates in establishing a clonally diverse population of T cells recognizing a polymorphic ligand. Isotypic exclusion does not apply to the gamma gene, however, suggesting different roles for the different gamma gene isotypes.

Relationship of the genes for Chediak-Higashi syndrome (beige) and the T-cell receptor gamma chain in mouse and man

The genetic linkage of Chediak-Higashi syndrome and its murine analog, beige (bg), to the T-cell receptor (TCR-gamma) gamma chain gene is further defined. Previous studies using recombinant inbred strains of mice demonstrated that the murine bg gene is genetically linked to a murine TCR-gamma gene. We report that in the mouse the frequency of recombination between these two markers is 0.025. Further, we tested the hypothesis that these two genes are linked in the human genome by analyzing restriction fragment length polymorphisms (RFLPs) in five families with children afflicted with Chediak-Higashi syndrome. In three families, RFLPs in TCR-gamma genes were inherited discordantly from Chediak-Higashi syndrome, demonstrating nonlinkage. We postulate that there is an evolutionary chromosomal breakpoint between the bg gene and the TCR-gamma gene.

Chromosome maps of man and mouse, III

Data on loci whose positions are known in both man and mouse are presented in the form of chromosomal displays, a table, and autosomal and X-chromosomal grids. At least 40 conserved autosomal segments with two or more loci, as well as 17 homologous X-linked loci, are now known in the two species, in which mitochondrial DNA is also highly conserved. Apart from the Y, the only chromosome now lacking a conserved group is human 13. Human 17 has a single conserved group which includes both short and long arms, and so may have remained largely intact in mammalian evolution. Human and mouse chromosomal maps show the approximate locations of homologous genes while the mouse map also shows the positions of translocations used in gene location.

Genomic organization of the mouse T-cell receptor beta-chain gene family

We have combined three different methods, deletion mapping of T-cell lines, field-inversion gel electrophoresis, and the restriction mapping of a cosmid clone, to construct a physical map of the murine T-cell receptor beta-chain gene family. We have mapped 19 variable (V beta) gene segments and the two clusters of diversity (D beta) and joining (J beta) gene segments and constant (C beta) genes. These members of the beta-chain gene family span approximately equal to 450 kilobases of DNA, excluding one potential gap in the DNA fragment alignments.

Mammalian T-lymphocyte antigen receptor genes: genetic and nongenetic potential to generate variability

T lymphocytes of higher vertebrates are able to specifically recognize a seemingly unlimited number of foreign antigens via their receptors, the T cell antigen receptors (TCRs). T lymphocytes mature by passing through the thymus and acquire antigen specificity by expressing the TCR molecules on their cell surface. Genetic and somatic diversification mechanisms give rise to the enormous degree of TCR variability observed in mature T cells: germline and combinatorial diversity as well as junctional and the so-called N-region diversity. In contrast to the situation in immunoglobulin genes somatic hypermutation does not seem to play a significant role in TCR diversification. It is argued here that the enzyme terminal nucleotidyl-transferase is potentially a major factor in generating the immense diversity. We propose furthermore that this enzyme ensures the flexibility of T cell responses to novel antigens by random insertion of so-called N-region nucleotides. Apart from the physiological functions of TCR genes any involvement in the etiology of T cell neoplasia remains to be proven.

Chromosomal locations of the gene coding for the CD3 (T3) gamma subunit of the human and mouse CD3/T-cell antigen receptor complexes

The gene coding for the Mr 26000 gamma chain of the human CD3 (T3) antigen/T-cell antigen receptor complex was mapped to chromosome band 11q23 by using a cDNA clone (pJ6T3 gamma-2), by in situ hybridization to metaphase chromosomes and by Southern blot analysis of a panel of human-rodent somatic cell hybrids. The mouse homolog, here termed Cdg-3, was mapped to chromosome 9 using the mouse gamma cDNA clone pB10.AT3 gamma-1 and a panel of mouse-hamster somatic cell hybrids. Similar locations for the CD3 delta genes have been described previously. Thus, the corporate results indicate that the CD3 gamma and delta genes have remained together since they duplicated about 200 million years ago.