Immunodominance in the TCR repertoire of a [corrected] TCR peptide-specific CD4+ Treg population that controls experimental autoimmune encephalomyelitis

Immunodominance in self-Ag-reactive pathogenic CD4(+) T cells has been well established in several experimental models. Although it is clear that regulatory lymphocytes (Treg) play a crucial role in the control of autoreactive cells, it is still not clear whether immunodominant CD4(+) Treg clones are also involved in control of autoreactivity. We have shown that TCR-peptide-reactive CD4(+) and CD8(+) Treg play an important role in the spontaneous recovery and resistance from reinduction of experimental autoimmune encephalomyelitis in B10.PL mice. We report, by sequencing of the TCR alpha- and beta-chain associated with CD4(+) Treg, that the TCR repertoire is limited and the majority of CD4(+) Treg use the TCR Vbeta14 and Valpha4 gene segments. Interestingly, sequencing and spectratyping data of cloned and polyclonal Treg populations revealed that a dominant public CD4(+) Treg clonotype expressing Vbeta14-Jbeta1.2 with a CDR3 length of 7 aa exists in the naive peripheral repertoire and is expanded during the course of recovery from experimental autoimmune encephalomyelitis. Furthermore, a higher frequency of CD4(+) Treg clones in the naive repertoire correlates with less severity and more rapid spontaneous recovery from disease in parental B10.PL or PL/J and (B10.PL x PL/J)F(1) mice. These findings suggest that unlike the Ag-nonspecific, diverse TCR repertoire among the CD25(+)CD4(+) Treg population, TCR-peptide-reactive CD4(+) Treg involved in negative feedback regulation of autoimmunity use a highly limited TCR V-gene repertoire. Thus, a selective set of immunodominant Treg as well as pathogenic T cell clones can be targeted for potential intervention in autoimmune disease conditions.     

Oligoclonality of rat intestinal intraepithelial T lymphocytes: overlapping TCR beta-chain repertoires in the CD4 single-positive and CD4/CD8 double-positive subsets

Previous studies in humans and mice have shown that gut intraepithelial lymphocytes (IELs) express oligoclonal TCR beta-chain repertoires. These studies have either employed unseparated IEL preparations or focused on the CD8+ subsets. Here, we have analyzed the TCR beta-chain repertoire of small intestinal IELs in PVG rats, in sorted CD4+ as well as CD8+ subpopulations, and important differences were noted. CD8alphaalpha and CD8alphabeta single-positive (SP) IELs used most Vbeta genes, but relative Vbeta usage as determined by quantitative PCR analysis differed markedly between the two subsets and among individual rats. By contrast, CD4+ IELs showed consistent skewing toward Vbeta17 and Vbeta19; these two genes accounted collectively for more than half the Vbeta repertoire in the CD4/CD8 double-positive (DP) subset and were likewise predominant in CD4 SP IELs. Complementarity-determining region 3 length displays and TCR sequencing demonstrated oligoclonal expansions in both the CD4+ and CD8+ IEL subpopulations. These studies also revealed that the CD4 SP and CD4/CD8 DP IEL subsets expressed overlapping beta-chain repertoires. In conclusion, our results show that rat TCR-alphabeta+ IELs of both the CD8+ and CD4+ subpopulations are oligoclonal. The limited Vbeta usage and overlapping TCR repertoire expressed by CD4 SP and CD4/CD8 DP cells suggest that these two IEL populations recognize restricted intestinal ligands and are developmentally and functionally related.     

Frequent contribution of T cell clonotypes with public TCR features to the chronic response against a dominant EBV-derived epitope: application to direct detection of their molecular imprint on the human peripheral T cell repertoire

In an attempt to provide a global picture of the TCR repertoire diversity of a chronic T cell response against a common Ag, we performed an extensive TCR analysis of cells reactive against a dominant HLA-A2-restricted EBV epitope (hereafter referred to as GLC/A2), obtained after sorting PBL or synovial fluid lymphocytes from EBV-seropositive individuals using MHC/peptide multimers. Although TCR beta-chain diversity of GLC/A2+ T cells was extensive and varied greatly from one donor to another, we identified in most cell lines several recurrent Vbeta subsets (Vbeta2, Vbeta4, and Vbeta16 positive) with highly conserved TCRbeta complementarity-determining region 3 (CDR3) length and junctional motifs, which represented from 11 to 98% (mean, 50%) of GLC/A2-reactive cells. While TCR beta-chains expressed by these subsets showed limited CDR1, CDR2, and CDR3 homology among themselves, their TCR alpha-chains comprised the same TCRAV region, thus suggesting hierarchical contribution of TCR alpha-chain vs TCR beta-chain CDR to recognition of this particular MHC/peptide complex. The common occurrence of T cell clonotypes with public TCR features within GLC/A2-specific T cells allowed their direct detection within unsorted PBL using ad hoc clonotypic primers. These results, which suggest an unexpectedly high contribution of public clonotypes to the TCR repertoire against a dominant epitope, have several implications for the follow-up and modulation of T cell-mediated immunity.     

The TCR repertoire of an immunodominant CD8+ T lymphocyte population

The TCR repertoire of an epitope-specific CD8(+) T cell population remains poorly characterized. To determine the breadth of the TCR repertoire of a CD8(+) T cell population that recognizes a dominant epitope of the AIDS virus, the CD8(+) T cells recognizing the tetrameric Mamu-A*01/p11C(,CM) complex were isolated from simian immunodeficiency virus (SIV)-infected Mamu-A*01(+) rhesus monkeys. This CD8(+) T cell population exhibited selected usage of TCR V beta families and complementarity-determining region 3 (CDR3) segments. Although the epitope-specific CD8(+) T cell response was clearly polyclonal, a dominance of selected V beta(+) cell subpopulations and clones was seen in the TCR repertoire. Interestingly, some of the selected V beta(+) cell subpopulations and clones maintained their dominance in the TCR repertoire over time after infection with SIV of macaques. Other V beta(+) cell subpopulations declined over time in their relative representation and were replaced by newly evolving clones that became dominant. The present study provides molecular evidence indicating that the TCR repertoire shaped by a single viral epitope is dominated at any point in time by selected V beta(+) cell subpopulations and clones and suggests that dominant V beta(+) cell subpopulations and clones can either be stable or evolve during a chronic infection.     

Circulating activated and effector memory T cells are associated with calcification and clonal expansions in bicuspid and tricuspid valves of calcific aortic stenosis

We sought to delineate further the immunological significance of T lymphocytes infiltrating the valve leaflets in calcific aortic stenosis (CAS) and determine whether there were associated alterations in circulating T cells. Using clonotypic TCR β-chain length and sequence analysis we confirmed that the repertoire of tricuspid CAS valves contains numerous expanded T cell clones with varying degrees of additional polyclonality, which was greatest in cases with severe calcification. We now report a similar proportion of clonal expansions in the much younger bicuspid valve CAS cases. Peripheral blood flow cytometry revealed elevations in HLA-DR(+) activated CD8 cells and in the CD8(+)CD28(null)CD57(+) memory-effector subset that were significantly greater in both bicuspid and tricuspid CAS cases with more severe valve calcification. Lesser increases of CD4(+)CD28(null) T cells were identified, principally in cases with concurrent atherosclerotic disease. Upon immunostaining the CD8 T cells in all valves were mainly CD28(null), and CD8 T cell percentages were greatest in valves with oligoclonal repertoires. T cell clones identified by their clonotypic sequence as expanded in the valve were also found expanded in the circulating blood CD28(null)CD8(+) T cells and to a lesser degree in the CD8(+)CD28(+) subset, directly supporting the relationship between immunologic events in the blood and the valve. The results suggest that an ongoing systemic adaptive immune response is occurring in cases with bicuspid and tricuspid CAS, involving circulating CD8 T cell activation, clonal expansion, and differentiation to a memory-effector phenotype, with trafficking of T cells in expanded clones between blood and the valve.     

Influence of the route of infection on development of T-cell receptor beta-chain repertoires of reovirus-specific cytotoxic T lymphocytes

It is well established that the route of infection affects the nature of the adaptive immune response. However, little is known about the effects of the route of exposure on development of cytotoxic T-lymphocyte (CTL) responses. Alternative antigen-presenting cell populations, tissue-restricted expression of class I major histocompatibility complex-encoded molecules, and unique T-cell receptor (TCR)-bearing cells in mucosal tissues could influence the selection and expansion of responder T cells. This study addresses the question of whether the route of virus infection affects the selection and expansion of subpopulations of virus-specific CTLs. Mice were infected orally or in the hind footpads with reovirus, and the repertoires of TCR beta-chains expressed on virus-specific CD8(+) T cells in Peyer's patches or lymph nodes and spleens were examined. CD8(+) cells expressing the variable gene segment of the TCR beta-chain 6 (Vbeta6) expanded in the spleens of mice infected by either route and in CTL lines established from the spleens and draining lymphoid tissues. Adoptively transferred Vbeta6(+) CD8(+) T cells from orally or parenterally infected donors expanded in reovirus-infected severe combined immunodeficient recipient mice and mediated cytotoxicity ex vivo. Furthermore, recovered Vbeta6(+) cells were enriched for clones utilizing uniform complementarity-determining region 3 (CDR3) lengths. However, sequencing of CDR3beta regions from Vbeta6(+) CD8(+) cells indicated that Jbeta gene segment usage is significantly more restricted in CTLs from orally infected mice, suggesting that the route of infection affects selection and/or subsequent expansion of virus-specific CTLs.     

Anti-TCR antibody treatment activates a novel population of nonintestinal CD8 alpha alpha+ TCR alpha beta+ regulatory T cells and prevents experimental autoimmune encephalomyelitis

CD8alphaalpha+CD4-TCRalphabeta+ T cells are a special lineage of T cells found predominantly within the intestine as intraepithelial lymphocytes and have been shown to be involved in the maintenance of immune homeostasis. Although these cells are independent of classical MHC class I (class Ia) molecules, their origin and function in peripheral lymphoid tissues are unknown. We have recently identified a novel subset of nonintestinal CD8alphaalpha+CD4-TCRalphabeta+ regulatory T cells (CD8alphaalpha Tregs) that recognize a TCR peptide from the conserved CDR2 region of the TCR Vbeta8.2-chain in the context of a class Ib molecule, Qa-1a, and control- activated Vbeta8.2+ T cells mediating experimental autoimmune encephalomyelitis. Using flow cytometry, spectratyping, and real-time PCR analysis of T cell clones and short-term lines, we have determined the TCR repertoire of the CD8alphaalpha regulatory T cells (Tregs) and found that they predominantly use the TCR Vbeta6 gene segment. In vivo injection of anti-TCR Vbeta6 mAb results in activation of the CD8alphaalpha Tregs, inhibition of the Th1-like pathogenic response to the immunizing Ag, and protection from experimental autoimmune encephalomyelitis. These data suggest that activation of the CD8alphaalpha Tregs present in peripheral lymphoid organs other than the gut can be exploited for the control of T cell-mediated autoimmune diseases.     

CTL recognition of a protective immunodominant influenza A virus nucleoprotein epitope utilizes a highly restricted Vbeta but diverse Valpha repertoire: functional and structural implications

To investigate protective immunity conferred by CTL against viral pathogens, we have analyzed CD8(+) T cell responses to the immunodominant nucleoprotein epitope (NP(366-374)) of influenza A virus in B6 mice during primary and secondary infections in vivo. Unlike the highly biased TCR Vbeta repertoire, the associated Valpha repertoire specific for the NP(366-374)/D(b) ligand is quite diverse. Nonetheless, certain public and conserved CDR3alpha clonotypes with distinct molecular signatures were identified. Pairing of public Valpha and Vbeta domains creates an alphabeta TCR heterodimer that binds efficiently to the NP(366-374)/D(b) ligand and stimulates T cell activation. In contrast, private TCRs, each comprising a distinct alpha chain paired with the same public beta chain, interact very differently. Molecular dynamics simulation reveals that the conformation and mobility of the shared Vbeta CDR loops are governed largely by the associated Valpha domains. These results provide insight into molecular principles regarding public versus private TCRs linked to immune surveillance after infection with influenza A virus.     

V beta 6+ T cells are obligatory for vaccine-induced immunity to Histoplasma capsulatum

We examined TCR usage to a protective fragment of heat shock protein 60 from the fungus, Histoplasma capsulatum. Nearly 90% of T cell clones from C57BL/6 mice vaccinated with this protein were Vbeta6+; the remainder were Vbeta14+. Amino acid motifs of the CDR3 region from Vbeta6+ cells were predominantly IxGGG, IGG, or SxxGG, whereas it was uniformly SFSGG for Vbeta14+ clones. Short term T cell lines from Vbeta6+-depleted mice failed to recognize Ag, and no T cell clones could be generated. To determine whether Vbeta6+ cells were functionally important, we eliminated them during vaccination. Depletion of Vbeta6+ cells abrogated protection in vivo and upon adoptive transfer of cells into TCR alphabeta(-/-) mice. Transfer of a Vbeta6+, but not a Vbeta14+, clone into TCR alphabeta(-/-) mice prolonged survival. Cytokine generation by Ag-stimulated splenocytes from immunized mice depleted of Vbeta6+ cells was similar to that of controls. The efficacy of the Vbeta6+ clone was associated with elevated production of IFN-gamma, TNF-alpha, and GM-CSF compared with that of the Vbeta14+ clone. More Vbeta6+ cells were present in lungs and spleens of TCR alphabeta(-/-) on day 3 postinfection compared with Vbeta14+ cells. Thus, a single Vbeta family was essential for vaccine-induced immunity. Moreover, the mechanism by which Vbeta6+ contributed to protective immunity differed between unfractionated splenocytes and T cell clones.     

Reconstitution of CD8+ T cells by retroviral transfer of the TCR alpha beta-chain genes isolated from a clonally expanded P815-infiltrating lymphocyte

Gene transfer of TCR alphabeta-chains into T cells may be a promising strategy for providing valuable T lymphocytes in the treatment of tumors and other immune-mediated disorders. We report in this study the reconstitution of CD8(+) T cells by transfer of TCR alphabeta-chain genes derived from an infiltrating T cell into P815. Analysis of the clonal expansion and Vbeta subfamily usage of CD8(+) TIL in the tumor sites demonstrated that T cells using Vbeta10 efficiently infiltrated and expanded clonally. The TCR alpha- and beta-chain sequences derived from a tumor-infiltrating CD8(+)/Vbeta10(+) single T cell clone (P09-2C clone) were simultaneously determined by the RT-PCR/single-strand conformational polymorphism method and the single-cell PCR method. When P09-2C TCR alphabeta-chain genes were retrovirally introduced into CD8(+) T cells, the reconstituted T cells positively lysed the P815 tumor cells, but not the A20, EL4, or YAC-1 cells, in vitro. In addition, the CTL activity was blocked by the anti-H2L(d) mAb. Furthermore, T cells containing both TCR alpha- and beta-chains, but not TCR beta-chain alone, accumulated at the tumor-inoculated site when the reconstituted CD8(+) T cells were adoptively transferred to tumor-bearing nude mice. These findings suggest that it is possible to reconstitute functional tumor-specific CD8(+) T cells by transfer of TCR alphabeta-chain genes derived from TIL, and that such T cells might be useful as cytotoxic effector cells or as a vehicle for delivering therapeutic agents.     

Psoriatic arthritis joint fluids are characterized by CD8 and CD4 T cell clonal expansions appear antigen driven

The CD8 alphabetaT cell receptor repertoire in joint fluid of individuals with active psoriatic arthritis contained an average of 32 major oligoclonal expansions in many variable genes of the TCR beta chain (BV) families, as shown by beta-chain CDR3 length analysis. Interestingly, a small number of oligoclonal expansions were shared between simultaneous samples of joint fluid and blood; however, most expansions found in joint fluid were not identifiable in blood emphasizing the immunologic specificity of the clonal events for the inflamed joint at a given point of time. The CD4 T cell joint fluid repertoire contained fewer and smaller oligoclonal expansions also largely restricted to the joint, suggesting that CD4 T cells participate perhaps by interacting cognitively to generate the CD8 clones. The inferred amino acid sequence of a single CD8 oligoclonal expansion revealed that they usually are composed of one or a few structurally related clones at the amino acid sequence level with beta-chains that encode identical or highly homologous CDR3 motifs. These were not shared among patients. Moreover, several clones that encoded the same amino acid sequence were found to be structurally distinct at the nucleotide level, strongly implying clonal selection and expansion is operating at the level of specific TCR-peptide interactions. The findings support a model of psoriatic arthritis inflammation involving extensive and selective Ag, likely autoantigen, driven intra-articular CD4, and CD8 T cell clonal expansions.     

Public T cell receptor beta-chains are not advantaged during positive selection

Studies of human and murine T cells have shown that public TCR beta-chain rearrangements can dominate the Ag-specific and naive repertoires of distinct individuals. We show that mouse T cells responding to the minor histocompatibility Ag HYDbSmcy share an invariant Vbeta8.2-Jbeta2.3 TCR gene rearrangement. The dominance of this rearrangement shows that it successfully negotiated thymic selection and was highly favored during clonal expansion in all animals examined. We hypothesized that such beta-chains are advantaged during thymic and/or peripheral selection and, as a result, may be over-represented in the naive repertoire. A sequencing study was undertaken to examine the diversity of Vbeta8.2-Jbeta2.3 CDR3 loops from naive T cell repertoires of multiple mice. Public TCR beta-chain sequences were identified across different repertoires and MHC haplotypes. To determine whether such public beta-chains are advantaged during thymic selection, individual chains were followed through T cell development in a series of novel bone marrow competition chimeras. We demonstrate that beta-chains were positively selected with similar efficiency regardless of CDR3 loop sequence. Therefore, the establishment and maintenance of public beta-chains in the periphery is predominantly controlled by post-thymic events through modification of the primary, thymus-derived TCR repertoire.     

Valpha24-JalphaQ-independent,CD1d-restricted recognition of alpha-galactosylceramide by human CD4(+) and CD8alphabeta(+) T lymphocytes

Human CD1d molecules present an unknown ligand, mimicked by the synthetic glycosphingolipid alpha-galactosylceramide (alphaGC), to a highly conserved NKT cell subset expressing an invariant TCR Valpha24-JalphaQ paired with Vbeta11 chain (Valpha24(+)Vbeta11(+) invariant NK T cell (NKT(inv))). The developmental pathway of Valpha24(+)Vbeta11(+)NKT(inv) is still unclear, but recent studies in mice were consistent with a TCR instructive, rather than a stochastic, model of differentiation. Using CD1d-alphaGC-tetramers, we demonstrate that in humans, TCR variable domains other than Valpha24 and Vbeta11 can mediate specific recognition of CD1d-alphaGC. In contrast to Valpha24(+)Vbeta11(+)NKT(inv) cells, Valpha24(-)/CD1d-alphaGC-specific T cells express either CD8alphabeta or CD4 molecules, but they are never CD4 CD8 double negative. We show that CD8alphabeta(+)Valpha24(-)/CD1d-alphaGC-specific T cells exhibit CD8-dependent specific cytotoxicity and have lower affinity TCRs than Valpha24(+)/CD1d-alphaGC-specific T cells. In conclusion, our results demonstrate that, contrary to the currently held view, recognition of CD1d-alphaGC complex in humans is not uniformly restricted to the Valpha24-JalphaQ/Vbeta11 NKT cell subset, but can be mediated by a diverse range of Valpha and Vbeta domains. The existence of a diverse repertoire of CD1d-alphaGC-specific T cells in humans strongly supports their Ag-driven selection.     

A NK1.1+ thymocyte-derived TCR beta-chain transgene promotes positive selection of thymic NK1.1+ alpha beta T cells

As a consequence of the peptide specificity of intrathymic positive selection, mice transgenic for a rearranged TCR beta-chain derived from conventional alphabeta T lymphocytes frequently carry mature T cells with significant skewing in the repertoire of the companion alpha-chain. To assess the generality of such an influence, we generated transgenic (Tg) mice expressing a beta-chain derived from nonclassical, NK1.1+ alphabeta T cells, the thymus-derived, CD1. 1-specific DN32H6 T cell hybridoma. Results of the sequence analysis of genomic DNA from developing DN32H6 beta Tg thymocytes revealed that the frequency of the parental alpha-chain sequence, in this instance the Valpha14-Jalpha281 canonical alpha-chain, is specifically and in a CD1.1-dependent manner, increased in the postselection thymocyte population. In accordance, we found phenotypic and functional evidence for an increased frequency of thymic, but interestingly not peripheral, NK1.1+ alphabeta T cells in DN32H6 beta Tg mice, possibly indicating a thymic determinant-dependent maintenance. Thus, in vivo expression of the rearranged TCR beta-chain from a thymus-derived NK1.1+ Valpha14+ T cell hybridoma promotes positive selection of thymic NK1.1+ alphabeta T cells. These observations indicate that the strong influence of productive beta-chain rearrangements on the TCR sequence and specificity of developing thymocytes, which operates through positive selection on self-determinants, applies to both classical and nonclassical alphabeta T cells and therefore represents a general phenomenon in intrathymic alphabeta T lymphocyte development.     

Large and dissimilar repertoire of Melan-A/MART-1-specific CTL in metastatic lesions and blood of a melanoma patient

It is widely accepted that the repertoire of Melan-A-specific T cells naturally selected in melanoma patients is diverse and mostly nonoverlapping among different individuals. To date, however, no studies have addressed the TCR profile in different tumor sites and the peripheral blood from the same patient. We compared the TCR usage of Melan-A-specific T cells from different compartments of a single melanoma patient to evaluate possible clonotype expansion or preferential homing over a 4-mo follow-up period. Using HLA-A2 peptide tetramers, CD8(+) T cells recognizing the modified Melan-A immunodominant ELAGIGILTV peptide were isolated from four metastatic lesions resected from a single melanoma patient, and their TCR repertoire was studied. A panel of T cell clones was generated by cell cloning of tetramer-positive cells. Analysis of the TCR beta-chain V segment and the complementarity-determining region 3 (CDR3) length and sequence revealed a large diversity in the TCR repertoire, with only some of the clones showing a partial conservation in the CDR3. A similar degree of diversity was found by analyzing a number of T cell clones obtained after sorting a Melan-A-specific population derived from PBLs of the same patient after in vitro culture with the immunodominant epitope. Moreover, clonotypes found at one site were not present in another, suggesting the lack of expansion and circulation of one or more clonotypes. Taken together, these results buttress the notion that the CTLs recognizing the immunodominant Ag of Melan-A comprise a high number of different clonotypic TCR, of which only some exhibit common features in the CDR3.     

Contribution of T-cell receptor repertoire breadth to the dominance of epitope-specific CD8+ T-lymphocyte responses

Dominant epitope-specific CD8(+) T-lymphocyte responses play a central role in controlling viral spread. We explored the basis for the development of this focused immune response in simian immunodeficiency virus (SIV)- and simian-human immunodeficiency virus (SHIV)-infected rhesus monkeys through the use of two dominant (p11C and p199RY) and two subdominant (p68A and p56A) epitopes. Using real-time PCR to quantitate T-cell receptor (TCR) variable region beta (Vbeta) family usage, we show that CD8(+) T-lymphocyte populations specific for dominant epitopes are characterized by a diverse Vbeta repertoire, whereas those specific for subdominant epitopes employ a dramatically more focused Vbeta repertoire. We also demonstrate that dominant epitope-specific CD8(+) T lymphocytes employ TCRs with multiple CDR3 lengths, whereas subdominant epitope-specific cells employ TCRs with a more restricted CDR3 length. Thus, the relative dominance of an epitope-specific CD8(+) T-lymphocyte response reflects the clonal diversity of that response. These findings suggest that the limited clonal repertoire of subdominant epitope-specific CD8(+) T-lymphocyte populations may limit the ability of these epitope-specific T-lymphocyte populations to expand and therefore limit the ability of these cell populations to contribute to the control of viral replication.     

Oligoclonality of CD8+ T cells in breast cancer patients.

Substantial evidence has suggested that T cells play an important role in antitumor immunity. T cells with cytotoxic activity against tumors have been isolated from in vitro culture of tumor-infiltrated lymphocytes of cancer patients. In addition, clonal expansions of T cells have been identified in lesions of tumors by using a PCR-based CDR3 analysis of T cell receptors (TCR). Since the CDR3 region of the T cell receptor directly interacts with the antigen-MHC complex and is thus highly polymorphic, a dominant CDR3 length in a particular TCR V beta population will indicate the clonal expansion of a specific T cell clone. Utilizing this technique, we have analyzed the T cell repertoire in lymph nodes (LNs) and peripheral blood of 20 breast cancer patients. Our results show that in most cases, peripheral blood mononuclear cells (PB-MCs) and LN express dominant CD8+ T cell clones in different V beta gene families, and the number of dominant clones is higher in PBMC than in the LN. Furthermore, in 7 out of 16 patients' lymph nodes, there is a dominant V beta 18 T cell clonal expansion in the CD8+ T cell subset. The frequency of an oligoclonal expansion of V beta 18 CD8+ T cells in non-breast cancer lymph nodes is 1 out of 9, but no obvious motif in the CDR3 region of V beta 18 TCR can be identified. The prevalence of the clonal dominance found in breast cancer is discussed in the context of a possible tumor-related antigen stimulation.     

Effective control of chronic gamma-herpesvirus infection by unconventional MHC Class Ia-independent CD8 T cells

Control of virus infection is mediated in part by major histocompatibility complex (MHC) Class Ia presentation of viral peptides to conventional CD8 T cells. Although important, the absolute requirement for MHC Class Ia-dependent CD8 T cells for control of chronic virus infection has not been formally demonstrated. We show here that mice lacking MHC Class Ia molecules (K(b-/-)xD(b-/-) mice) effectively control chronic gamma-herpesvirus 68 (gammaHV68) infection via a robust expansion of beta2-microglobulin (beta2-m)-dependent, but CD1d-independent, unconventional CD8 T cells. These unconventional CD8 T cells expressed: (1) CD8alphabeta and CD3, (2) cell surface molecules associated with conventional effector/memory CD8 T cells, (3) TCRalphabeta with a significant Vbeta4, Vbeta3, and Vbeta10 bias, and (4) the key effector cytokine interferon-gamma (IFNgamma). Unconventional CD8 T cells utilized a diverse TCR repertoire, and CDR3 analysis suggests that some of that repertoire may be utilized even in the presence of conventional CD8 T cells. This is the first demonstration to our knowledge that beta2-m-dependent, but Class Ia-independent, unconventional CD8 T cells can efficiently control chronic virus infection, implicating a role for beta2-n-dependent non-classical MHC molecules in control of chronic viral infection. We speculate that similar unconventional CD8 T cells may be able to control of other chronic viral infections, especially when viruses evade immunity by inhibiting generation of Class Ia-restricted T cells.