Molecular genetic analysis of 178 I-Abm12-reactive T cells

Increased frequency of 2,4,6-trinitrophenyl (TNP)-specific, H-2b-restricted cytotoxic T lymphocyte precursors in transgenic mice expressing a T cell receptor beta chain gene from an H-2b-restricted, TNP-specific cytolytic T cell clone

T cell antigen receptors (TcR) expressing V alpha 10/J alpha BBM142 genes in association with beta chains containing J beta 2.6 elements were found to be predominant among 2,4,6-trinitrophenyl (TNP)-specific, H-2b-restricted cytolytic T cell lines (CTL). To assess the relative contribution of the TcR beta chain to the TNP specificity as well as to the selection of the respective TcR alpha chain elements we generated transgenic mice expressing the TcR beta chain of the H-2b/TNP-specific CTL clone BT7.4.1. The TcR of this clone does not belong to the type predominant among H-2b/TNP-specific CTL, as it consists of an alpha chain encoded by a V alpha 8/J alpha DO gene rearrangement and a V beta 2/J beta 1.1-containing beta chain. In the transgenic mice almost all T cells exclusively express the transgenic V beta 2 gene, as a result of allelic exclusion. TNP-specific, H-2b-restricted precursors were found at 7- to 8-fold higher frequency in these mice as compared with non-transgenic littermates. In H-2b/d heterozygous transgenic mice, an increased frequency of TNP-specific precursors was found only in H-2b, but not in H-2d-restricted CTL. Analysis of H-2b/TNP-specific CTL lines derived from V beta 2-transgenic mice indicated a preferential association of the transgenic TcR beta chain with endogenous alpha chains encoded by V alpha 8 and J alpha BBM142 genes. This suggests that the hapten TNP is recognized like typical peptide antigens by combinatorial TcR alpha and beta contact sites.

Mouse autoreactive gamma/delta T cells. II. Molecular characterization of the T cell receptor

A panel of dendritic epidermal T cell (DETC) lines, and hybridomas derived from them, has been shown to spontaneously secrete lymphokines in the absence of added stimuli, which suggests that these cells are autoreactive. These cell lines are characterized by the expression of a V gamma 1.1C gamma 4/V delta 6 type T cell receptor (TcR), but several of the DETC lines also express a second TcR. Sequence analyses of these gamma/delta TcR revealed that the gamma chains were identical and that the delta chains, while not identical, were quite restricted in diversity, indicating that these receptors may recognize a common or closely related group of antigens. Analysis of hybridomas derived from newborn thymocytes identified six hybridomas that spontaneously secrete lymphokines. Five hybrids expressed a V gamma 1.1C gamma 4/V delta 6 receptor and one hybrid a V gamma 1.1C gamma 4/V delta 4 receptor that had a close structural relationship to the DETC gamma/delta TcR associated with spontaneous lymphokine secretion. gamma/delta TcR of the C gamma 4 type expressed by splenic hybridomas that did not spontaneously secrete lymphokines revealed no such relationship. Curiously, like the DETC, several of the thymocyte hybridomas that spontaneously secreted lymphokines expressed a second TcR, V gamma 2C gamma 1 or V gamma 3C gamma 1, apparently in association with the same delta chain that paired with the C gamma 4 chain. The presence of spontaneous lymphokine-secreting gamma/delta T cells with such highly homologous TcR in both the thymus and skin suggests a thymic origin for the autoreactive DETC and that these cells recognize a common or closely related group of self-antigens.

The T cell receptor/CD3 complex is composed of at least two autonomous transduction modules

Recent studies have demonstrated that the CD3-zeta subunit of the T cell antigen receptor (TCR) complex is involved in signal transduction. However, the function of the remaining invariant subunits, CD3-gamma, -delta, and epsilon, is still poorly understood. To examine their role in TCR function, we have constructed TCR/CD3 complexes devoid of functional zeta subunit and showed that they are still able to trigger the production of interleukin-2 in response to antigen or superantigen. These data, together with previous results, indicate that the TCR/CD3 complex is composed of at least two parallel transducing units, made of the gamma delta epsilon and zeta chains, respectively. Furthermore, the analysis of partially truncated zeta chains has led us to individualize a functional domain that may have constituted the building block of most of the transducing subunits associated with antigen receptors and some Fc receptors.

T-cell receptor V beta selectivity in T-cell clones alloreactive to HLA-Dw14

The HLA-DR4 subtypes Dw14 and Dw4 are T-cell-defined allospecificities encoded by the DRB1*0404 and DRB1*0401 genes, respectively. Although these allelic subtypes differ in only two amino acids, allorecognition between Dw14 and Dw4-positive individuals is brisk. This provides an opportunity to analyze T-cell receptor (TCR) usage in a very limited and specifically targeted case, namely the Dw4 anti-Dw14 allogeneic T-cell response. The variable (V), diversity (D), and joining (J) region sequences of the TCR beta chain from two different Dw14-specific alloreactive T-cell clones derived from a Dw4 donor were examined. Clone EMO25 recognized the Dw14.1, Dw14.2, and Dw15 subtypes, which share a DRB1 polymorphism at codon 71 on a DR4 background, while clone EMO36 reacted with only the Dw14.1 subtype associated with polymorphisms at codons 71 and 86. TCR beta cDNA from each clone was amplified using an anchored polymerase chain reaction (PCR) and subsequently expanded with V beta- and C beta-specific primers for asymmetric PCR and direct DNA sequencing. Both clones were found to express the same TCR V beta 8.2 gene segment; however, they have several different residues within the V beta-D beta-J beta junctional regions. V beta 8 usage was also enriched in polyclonal cells obtained from mixed lymphocyte cultures performed between the Dw4 and Dw14 responder-stimulator combination from which EMO25 and EMO36 were derived.

Retroviral super-antigens and T cells

For many years immunologists have been intrigued by a series of potent antigens encoded in the murine genome. These antigens, originally termed minor lymphocyte stimulating (Mls) antigens, are capable of inducing extremely strong T cell proliferative responses when presented in the context of MHC class II molecules. Recently, Mls antigens have been shown to stimulate T cells bearing particular T cell receptor V beta elements, leading to the designation of super-antigens. The endogenous expression of these super-antigens in mice results in the clonal elimination of large numbers of T cells in order to maintain self-tolerance. In this review we discuss the recent identification of endogenous super-antigens as retroviral gene products. In addition, we analyze the role of class II MHC molecules in the presentation of endogenous super-antigens to T cells. Finally, we discuss the dramatic effect of retroviral super-antigens on the T cell repertoire.

Endogenous superantigen expression is controlled by mouse mammary tumor proviral loci

Superantigens are defined by their ability to stimulate T cells based predominantly on their V beta expression and ability to delete T cells in the thymus when expressed endogenously. We show here that the expression of one endogenous superantigen, Etc-1, is controlled by the expression of the open reading frame region of the 3' long terminal repeat of the mouse mammary tumor proviral gene, Mtv-9. We show that Mtv-8 controls a superantigen with similar specificity, and that both Mtv-8 and Mtv-9 stimulate some V beta 17+ T cells. A third provirus, Mtv-6, controls a superantigen with specificity for V beta 3. Data presented raise the possibility that endogenous superantigens may compete for class II molecules in a single B cell.

Limitations in plasticity of the T-cell receptor repertoire

How constrained is T-cell recognition? Is a truncated T-cell receptor (TCR) repertoire, missing half of its V beta components (where V indicates variable), still broad enough to produce an antigen-specific T-cell response to all determinants? These questions can be answered for certain T-cell antigenic determinants whose response in the wild type is limited to specific gene segments. Our results show that mice with such a deletion in their TCR V beta genes (V beta truncated haplotype, Va beta) are unable to respond to two antigen determinants (sperm whale myoglobin 111-121/I-Ed and myelin basic protein 1-11/I-Au) whose response in the wild type is restricted to the missing V beta (V beta 8.2 in the case of 111-121/I-Ed and V beta 8.2 and V beta 13 in the case of 1-11/I-Au) gene segments. Fundamentally, this restriction could have been attributed to another aspect of immunodominance--that a favored TCR with high affinity would dominate the response, but in its absence, a hierarchy of T cells with lesser efficiency and expressing alternate TCR V genes could take over. However, from our experiments it has become evident that there is an absolute limit to the flexibility inherent in the TCR repertoire. Since it is clear that mouse populations have many ambient deletion ligands (such as self-superantigens) that can result in the loss of multiple V beta gene segments during normal T-cell development, these deletions can have serious consequences, such as unresponsiveness to the antigen as a whole--a hole in the repertoire--if a dominant determinant of that antigen normally shows restricted TCR V beta gene usage.

Extensive conservation of alpha and beta chains of the human T-cell antigen receptor recognizing HLA-A2 and influenza A matrix peptide

The major histocompatibility complex class I molecule HLA-A2.1 presents the influenza A virus matrix peptide 57-68 to cytotoxic T lymphocytes in all individuals with this common HLA type and is among the most thoroughly studied immune responses in humans. We have studied the T-cell receptor (TCR) heterogeneity of T cells specific for HLA-A2 and influenza A matrix peptide using the polymerase chain reaction. The usage of V alpha and V beta sequences seen on these T cells is remarkably conserved as are certain junctional sequences associated with alpha and beta chains. Furthermore, two unrelated HLA-A2 individuals have a similar pattern of TCR usage, implying that this is a predominant response in HLA-A2 populations. Analysis in one individual showed that the conserved TCR V alpha and V beta genes are minor members of the peripheral blood TCR repertoire. The sequences provide important information on the TCR necessary for the final structural analysis of this ternary complex.

The impact of naturally occurring DR3 microvariants, DRw17 and DRw18, on T-cell allorecognition

The limited amino acid sequence differences between the DR3 microvariants, DRw17 and DRw18, are found in the second variable region of the DR beta chain (residues 26 and 28) as well as in framework residues 47 and 86. Using selected responder/stimulator combinations, alloproliferative T-lymphocyte clones (TLC) were generated which recognize either a supertypic DR3-related determinant(s) or only those T-cell recognition determinants created by the four amino acids which differ between DRw17 and DRw18. Results indicate that the microvariation creates potent T-cell recognition determinants while leaving the DR3-related determinant(s) unaffected. Several TLC were generated which recognize the DRw18 molecule strongly and the DRw52c molecule weakly reflecting the sequence similarity between these molecules. In addition, one TLC was generated which recognizes DRw18 and DRw14,Dw9 but not DRw14,Dw16 molecules, a result not predicted by linear amino acid sequence comparisons. The intricate and sometimes unpredictable allorecognition patterns observed demonstrate that the molecular context of a specific amino acid sequence is as important as the actual sequence in forming a T-cell recognition site and, thus, in shaping the immune response profile of a given allele.

Recent advances in the polymerase chain reaction

The polymerase chain reaction (PCR) has dramatically altered how molecular studies are conducted as well as what questions can be asked. In addition to simplifying molecular tasks typically carried out with the use of recombinant DNA technology, PCR has allowed a spectrum of advances ranging from the identification of novel genes and pathogens to the quantitation of characterized nucleotide sequences. PCR can provide insights into the intricacies of single cells as well as the evolution of species. Some recent developments in instrumentation, methodology, and applications of the PCR are presented in this review.

An endogenous retrovirus mediating deletion of alpha beta T cells?

A special class of self-antigens (endogenous superantigens) is capable of deleting many murine T cells on the basis of their expression of particular T-cell receptor V beta gene segments. In mice that endogenously express these antigens, tolerance is mediated in part by the clonal deletion of the relevant V beta-bearing T cells. The deletion of I-E-reactive V beta 5.2-bearing T cells is dependent on the coexpression of an I-E tolerogenic coligand (Etc)14 and the gene for one of these coligands, Etc-1, maps to chromosome 12, near the mouse mammary tumour viral integrant, Mtv-9. Here we report a perfect genetic linkage between Etc-1 and Mtv-9 and show that Etc-1 is also involved in the I-E-dependent deletion of T cells bearing V beta 5.1 and V beta 11 domains. We also demonstrate that Mtv-9 transcripts are present in B cells expressing Etc-1 and suggest that the coligand recognized by roughly 15% of all T lymphocytes is encoded by the Mtv-9 genome.

No recombinations between Tcra-V and Tcra-C gene segments in 669 backcross mice

Because T-cell receptor (Tcr) genes may possibly function as non-major histocompatibility complex (MHC) immune response genes or predispose for autoimmune diseases, it is important to know how these genes are inherited. We found that Bgl I-digested DNA of BALB/c, C3H, DBA/2, and C57BL/6 exhibited restriction enzyme fragment length polymorphisms (RFLPs) for the Tcra-V1, Tcra-V2, Tcra-V4, Tcra-V6, Tcra-V7, Tcra-V8, Tcra-V11, Tcra-V12, Tcra-V13, and Tcra-C gene segments. Inheritance of these RFLPs in 669 offspring from (BALB/c x C57BL/6) x BALB/c, (BALB/c x C57BL/6) x C57BL/6, (C57BL/6 x DBA2) x DBA/2, and (C57BL/6 x C3H) x C3H backcrosses was studied. Since we did not find any recombinations in the offspring, Tcra-V and Tcra-C gene segments are tightly linked and inherited as a haplotype. A peculiar finding was that 22 out of 103 (BALB/c x C57BL/6) x BALB/c offspring, heterozygous for Tcra-C, had deleted a C57BL/6 Tcra-V1 band as well as Tcra-V2 and Tcra-V4 bands. As will be discussed, this deletion is probably caused by heterogeneity in the C57BL/6 breeding stock of a commercial supplier. In seven BXD and BXH recombinant inbred strains with known recombinations between the Tcra-C and Es-10 loci, all Tcra-V RFLPs cosegregated with the Tcra-C RFLP. This finding agrees with the conclusion from our backcross studies; namely that Tcra-V and Tcra-C gene segments are tightly linked.

Participation of a dominant cytotoxic T cell population defined by a monoclonal antibody in syngeneic anti-tumor responses

Cytotoxic T lymphocyte (CTL) clones against a syngeneic Friend virus-induced erythroleukemia (FBL-3) were generated in C57BL/6 (B6) mice. A monoclonal antibody (mAb, N9-127) was then raised from spleen cells of a B6 mouse immunized syngenically against one of these CTL clones. This mAb detected the epitope (127Ep) of the T cell antigen receptor (TcR) on the immunizing CTL clone in tests of immunoprecipitation, specific blocking and proliferation, and induction of TcR-mediated nonspecific lysis of the clone. In addition, more than 10% of the FBL-3-specific CTL clones isolated independently from B6 mice were 127Ep+. Further investigations revealed that up to 30% of B6 anti-FBL-3 T cell blasts from mixed lymphocyte tumor cell cultures were positive for this epitope, and that its expression was confined to CD8+ T cells. This epitope was not detected in naive lymphoid cells from the spleen, lymph nodes or thymus or in T cell clones specific for tumors other than FBL-3. The FBL-3-specific CTL clones were next grouped into 127Ep+ and 127Ep- clones. Sequence analyses of the CTL clone used for immunization showed the rearrangements of V alpha 1J alpha 112-2 and V beta 10D beta 2.1J beta 2.7. Southern blot analysis of all the 127Ep+ CTL clones examined showed the same DNA rearrangement bands of both the TcR alpha and beta genes. These findings suggested that mAb N9-127 recognized the shared determinant of the TcR molecule which was expressed by the dominant CTL population in the response to FBL-3.

T cell receptor V beta gene usage in a human alloreactive response. Shared structural features among HLA-B27-specific T cell clones

A strategy, based on using V beta family-specific oligonucleotides, was developed for specific amplification and direct sequencing of human TCR V beta genes. With this strategy, it was possible to undertake a structural analysis of TCRs from human T cell clones in specific responses. 12 HLA-B27-specific cytotoxic clones were examined. The results reveal a nonrandom use of V beta gene diversity in this alloreactive response in that: (a) the clones express a restricted number of V beta segments, including a subset of V beta families that are significantly more related to one another than to most other V beta families; (b) five of seven clones having a particular reaction pattern with HLA-B27 subtypes possess Alanine at the D-J junction; and (c) identical J beta segments are found associated in several instances with identical or highly homologous V beta gene segments. In addition, two new V beta 13 members are reported.

Preferential usage of V alpha 4 and V beta 10 T cell receptor genes by lymphocytic choriomeningitis virus glycoprotein-specific H-2Db-restricted cytotoxic T cells

Correlations between the T cell receptor (TcR) V gene usage and the specificity of T cells have been primarily described for major histocompatibility complex (MHC) class II-restricted helper T cell responses. In the present study the TcR genes expressed by MHC class I-restricted murine cytotoxic T cells (CTL) specific for a major epitope of the lymphocytic choriomeningitis virus (LCMV), LCMV-GP2(275-289), were investigated. The TcR primary structure of an LCMV-GP2(275-289) specific H-2Db-restricted CTL clone has been determined. It uses a member of the V alpha 4 family joined to J alpha AN14.4 for the alpha chain and V beta 10 rearranged to D beta 2.1 and J beta 2.4 for its beta chain. Four other independent LCMV-GP2(275-289) specific H-2Db-restricted CTL clones also expressed V alpha 4 and V beta 10 gene elements. Furthermore, V alpha 4 and V beta 10 were preferentially expressed by polyclonal CTL of C57BL/6 origin specific for LCMV. These results suggest that both TcR V alpha and V beta regions are important for the recognition of the LCMV-GP2(275-289) epitope on H-2Db molecules.

Limited receptor repertoire in a mycobacteria-reactive subset of gamma delta T lymphocytes

The physiological role of lymphocytes bearing the gamma delta T-cell receptor (TCR) is still unclear. A function for a subset of these cells, however, is inferred from the finding that certain gamma delta chain-bearing lymphocytes are stimulated in a receptor-dependent fashion by mycobacterial antigens. We found that hybridomas derived from such cells in newborn murine thymus not only responded to mycobacterial purified protein derivative (PPD), but also exhibited an apparent autoreactivity. In neither response was haplotype-specific major histocompatibility (MHC) restriction demonstrable. To investigate the nature of antigen recognition by these gamma delta+ cells, we sequenced the gamma- and delta-chains from 28 PPD-reactive hybridomas, and found that a specific gamma-chain, together with one of a limited set of delta-chains, was needed to generate the PPD specificity. The reactive gamma delta pairs exhibited considerable junctional diversity, which may act to produce differences in the fine specificities of the responding cells.

The contribution of mutant amino acids to alloantigenicity

The I-Abm12 mutation has been used extensively to study the relationship between structure and function of murine class II major histocompatibility molecules. I-Abm12 differs from I-Ab by three amino acid replacements in the A beta chain, and the proposed structural model of the I-Abm12 molecule places these three amino acid substitutions along one of the alpha-helices where they may affect both antigen and TCR binding. Two of the substitutions, Ile----Phe67 and Thr----Lys71, are thought to point into the binding site, whereas the third substitution, Arg----Gln70, is thought to point up and hence, be available for binding to the TCR. These predicted orientations are consistent with serologic analysis of the bm12 molecule, which demonstrates that residue 70 is uniquely accessible to mAbs distinguishing I-Ab from I-Abm12. In this study we have determined the influence of each of these amino acid substitutions on the ability of the resulting molecules to stimulate a panel of I-Abm12 (allo) reactive T cell hybridomas. Our experiments indicate that reversion of the amino acid at position 70 from Gln (I-Abm12) to Arg (I-Ab) interferes with allorecognition by 33 of 35 I-Abm12-reactive hybridomas. On the other hand, many hybrids can tolerate amino acid substitutions at positions 67 or 71. Single amino acid substitutions at position 67, 70, or 71 are recognized by only a minority of I-Abm12-specific hybrids and usually the reactivity is greatly diminished. These data are most consistent with the idea that the amino acid at position 70 directly interacts with the TCR during allorecognition. The additional effects of residues 67 and 71 are consistent with a contribution by bound peptide to the allorecognition process.