Skewed TCR Repertoire Research Articles

CD4 depletion potentiates anti-tumor immunity in adoptive immunotherapy by increasing IL-18Rαhi endogenous CD8+ T cells

Abstract Adoptive T cell therapy (ACT) requires lympho-depletion pre-conditioning to eliminate immune-suppressive elements to allow for the efficient engraftment of adoptively transferred tumor-reactive T cells. Because anti-CD4 monoclonal antibody depletes CD4+ immune-suppressive cells to enhance anti-tumor immunity, combinations of anti-CD4 treatment and ACT have synergistic potential in cancer therapy. We designed a post-ACT conditioning regimen that involves weekly treatment with anti-CD4 (CD4post). Using murine melanoma, cyclophosphamide and tumor-reactive CD8+ T cell infusion were included to represent an ACT model. We evaluated anti-tumor effects and immunologic changes of T cells. CD4post in ACT markedly increased tumor suppression and survival. Remarkably, CD4post worked differently on ex vivo primed CD8+ T cells versus endogenous CD8+ T cells. CD4post substantially increased the proliferation of ex vivo primed CD8+ T cells, while increasing endogenous CD8+ T cell differentiation and effector function. Endogenous CD8+ T cells upregulated activation/exhaustion markers and exhibited a skewed TCR repertoire, implying that CD4post boosted tumor-reactivity. Accordingly, CD4post-experienced endogenous CD8+ T cells showed enhanced intra-tumoral infiltration and exhibited greater anti-tumor activity against melanoma in vitro. Importantly, enrichment of the IL-18Rαhi subset was critical for boosting anti-tumor responses, as IL-18Rα+ cell-depletion CD8+ T cells resulted in diminished anti-tumor activity. This study highlights the clinical relevance of CD4post to ACT and gives insights into the characteristics of the immunological components that drive the augmented cancer–immunity cycle in ACT.

Tumoral PD-1hiCD8+ T cells are partially exhausted and predict favorable outcome in triple-negative breast cancer.

Tumor-infiltrating PD-1hi dysfunctional CD8+ T cells have been identified in several tumors but largely unexplored in breast cancer (BC). Here we aimed to extensively explore PD-1hiCD8+ T cells in BC, focusing on the triple-negative BC (TNBC) subtype. Flow cytometry was used to study the phenotypes and functions of CD8+ T-cell subsets in peripheral blood and surgical specimens from treatment-naive BC patients. RNA-seq expression data generated to dissect the molecular features of tumoral PD-1neg, PD-1lo and PD-1hi CD8+ T cells. Further, the associations between tumoral PD-1hi CD8+ T cells and the clinicopathological features of 503 BC patients were explored. Finally, multiplexed immunohistochemistry (mIHC) was performed to evaluate in situ PD-1hiCD8+ T cells on the tissue microarrays (TMAs, n=328) for prognostic assessment and stratification of TNBC patients. PD-1hiCD8+ T cells found readily detectable in tumor tissues but rarely in peripheral blood. These cells shared the phenotypic and molecular features with exhausted and tissue-resident memory T cells (TRM) with a skewed TCR repertoire involvement. Interestingly, PD-1hiCD8+ T cells are in the state of exhaustion characterized by higher T-BET and reduced EOMES expression. PD-1hiCD8+ T cells found preferentially enriched within solid tumors, but predominant stromal infiltration of PD-1hiCD8+ T subset was associated with improved survival in TNBC patients. Taken together, tumoral PD-1hiCD8+ T-cell subpopulation in BC is partially exhausted, and their abundance signifies 'hot' immune status with favorable outcomes. Reinvigorating this population may provide further therapeutic opportunities in TNBC patients.

A novel simplified method of generating cytomegalovirus-specific cytokine-induced killer cells of high specificity and superior potency with GMP compliance

We describe a method of rendering polyclonal cytokine-induced killer cells (CIK) specific against cytomegalovirus (CMV), focusing on GMP compliance. Peripheral blood mononuclear cells (PBMNC) are stimulated with pooled CMV peptides pp65 and IE-1 for 16–24 h and the reactive T cell subset which up-regulate CD137 is further co-stimulated with anti-CD137, followed by expansion in G-Rex flasks under standard CIK culture condition. This method generates a large number CMV-specific CIK with superior potency compared to published method currently in clinical trials. The cytotoxicity as measured by chromium release assay correlates with the upregulation of CD107a upon peptide re-challenge as measured by flow cytometry. CMV-CIK at maturity consist of mainly late effector memory CD8 T cells and have a skewed TCR repertoire with preferential expansion of a few families. Such CMV-CIK retain their function after freezing and thawing. CMV-CIK thus generated is ready for clinical trial against drug-resistant CMV disease.

Alemtuzumab in Multiple Sclerosis: Short- and Long-Term Effects of Immunodepletion on the Peripheral Treg Compartment.

Treatment with alemtuzumab is followed by an early increase in Treg frequencies. Whether naïve and memory subsets are differentially affected and how depletion influences dysfunctional MS-Treg is unclear. In this study, we analyzed the effect of alemtuzumab on regulatory T-cells (Treg) in patients with multiple sclerosis (MS). For this purpose 182 blood samples from 25 MS patients were taken shortly before treatment and serially for up to 24 months after two alemtuzumab cycles. We studied Treg by flow cytometry (quantitation, phenotypical characterization), real-time polymerase chain reaction (T-cell receptor (TCR) excision circles [TREC] content), CDR3-spectratyping (clonal distribution), and proliferation assays (suppressive function). CD52-mediated cytolysis of Treg and conventional T-cells was determined by a complement-dependent cytolysis assay. Our studies revealed that 1 week post-alemtuzumab, Treg were depicted at constant frequencies among CD4+ T-cells. In contrast, Treg frequencies were massively increased at month 1. Post-depletional Treg exhibited a CD45RO+ memory phenotype, a skewed TCR repertoire, and contained minimum TREC numbers. Naïve Treg, thymic markers, and TCR-variability commenced to rise after 6 months but did not attain baseline levels. In vitro, Treg exhibited higher susceptibility to lysis than Tcon. Treg suppressive function constantly increased within 1 year when co-cultured with syngeneic T-cells, but remained stable against allogeneic T-cells from normal donors. Our findings suggest that (1) Treg are not spared from alemtuzumab-mediated depletion and thymopoiesis does not considerably contribute to long-term recovery, (2) either homeostatic proliferation and/or conversion from residual Tcon contributes to Treg expansion during the early post-treatment phase (3) the enhanced inhibitory effect of Treg following alemtuzumab is due to altered composition and reactivity of post-depletional Tcon.

Significant IFNγ responses of CD8+ T cells in CMV-seropositive individuals with autoimmune arthritis

BackgroundLatent Cytomegalovirus (CMV) infection accelerates immunosenescence in elderly with reactivations reported in Rheumatoid Arthritis (RA) and abnormal responses towards CMV in Juvenile Idiopathic Arthritis (JIA). ObjectivesConsidering the signs of premature T-cell immunosenescence in arthritis patients, the known effect of CMV latency on speeding up many of these signs in an age-dependent manner and the role of CMV on IFNγ-mediated inflammation in healthy elderly and RA, we hypothesized that latent CMV infection accelerates TCR repertoire restriction, loss of CD28, peripheral T-cell proliferation and aberrant IFNγ responses in arthritis patients. Study designUnspecific and CMVpp65-specific IFNγ responses were investigated in peripheral CD8+ T-cells in RA or JIA patients and healthy, age-matched controls. ResultsDespite higher prevalence and concentrations of IgG-anti-CMV, arthritis patients showed lower unspecific IFNγ production, lower CD69-mediated activation and lower CD8+ T-cell proliferation. CMV-seropositive RA patients showed higher intracellular IFNγ production and increased proportions of CD28-CD8+ T-cells after specific CMVpp65 long-term stimulation which was not altered by in vitro blockade of TNFα or IL-6. A skewed TCR repertoire towards oligoclonality and less polyclonality was found in JIA. DiscussionCMVpp65-specific IFNγ production with expansion of CD28-CD8+ T-cells suggests an efficient control of latent CMV regardless of immunosuppressive therapy or in vitro blockade of TNFα or IL-6 in CMV-seropositive arthritis patients. Increased IgG-anti-CMV antibody concentrations and increased proportions of intracellular IFNγ-producing CMVpp65-specific CD8+ T-cells in long-term cultures propose a possibly role of endogenous CMV reactivations boosting antibody levels and a higher possibly CMV-driven IFNγ-mediated inflammatory potential of CD8+ T-cells in arthritis patients.

Reduced and skewed TCR Vβ repertoire in CD8 compared to Foxp3+ regulatory T cells in acute gastrointestinal graft versus host disease (TRAN1P.947)

Abstract It is unclear if skewing of TCR repertoire in CD4, CD8 and Foxp3+Tregs plays a role in acute gastrointestinal (GI) GVHD. This prospective clinical study examined the TCR Vβ diversity among CD4, CD8 and Foxp3+Tregs from 18 adult patients (median age 53) post allogeneic stem cell transplant (SCT) at day 80 with acute GI GVHD (giGVHD, >grade 1, n=9) vs. nonGVHD (n=9). Fresh PBMC were analyzed by FACS using IOTest Beta Mark 24 TCR Vβ and Foxp3 (236A/E7)/Helios eBioscience kits. Mann Whitney test was used. Mean %CD4 was lower in giGVHD vs. nonGVHD (44vs72%, p=0.02) while no difference in %CD8 (51vs55%), %Tregs (16vs16%) and %Helios+Tregs (72vs76%). %Total Vβ were similar for CD4 (60), CD8 (60) and Tregs (64) in nonGVHD. In giGVHD, %CD8 (40) was lower than %Tregs (69), p<0.001 and %CD4 (56), p=0.08. Between giGVHD vs. nonGVHD, there was a difference for %TCR in CD8 (p=0.02) but none for CD4 or Tregs. In nonGVHD, there was a direct correlation between %CD8 TCR vs. %CD8 and %CD4 TCR vs. %CD4 but no correlation for %Treg TCR vs. %Tregs. In giGVHD, there was an inverse correlation between %CD8 TCR vs. %CD8 and %CD4 TCR vs. %CD4 but no correlation for %Treg TCR vs. %Tregs. These results indicate a restricted, reduced and skewed TCR repertoire within the CD8 as compared to Tregs and CD4 in giGVHD. These CD8 might be the pathogenic cells escaping Treg suppression. In conclusion, a reduced and skewed TCR diversity in CD8 at day 80 might be predictive for the development of chronic GVHD.

Helios+ FoxP3+ naturally occurring regulatory T cells are peripherally expanded in active systemic lupus erythematosus

BackgroundNaturally occurring FoxP3+ regulatory T cells (Tregs) are pivotal in induction and maintenance of tolerance to self and foreign antigens. Even though intensively studied, their role in systemic lupus erythematosus...

TCR Bias of In Vivo Expanded T Cells in Pancreatic Islets and Spleen at the Onset in Human Type 1 Diabetes

Autoreactive T cells, responsible for the destruction of pancreatic β cells in type 1 diabetes, are known to have a skewed TCR repertoire in the NOD mouse. To define the autoreactive T cell repertoire in human diabetes, we searched for intraislet monoclonal expansions from a recent onset in human pancreas to then trace them down to the patient's peripheral blood and spleen. Islet infiltration was diverse, but five monoclonal TCR β-chain variable expansions were detected for Vβ1, Vβ7, Vβ11, Vβ17, and Vβ22 families. To identify any sequence bias in the TCRs from intrapancreatic T cells, we analyzed 139 different CDR3 sequences. We observed amino acid preferences in the NDN region that suggested a skewed TCR repertoire within infiltrating T cells. The monoclonal expanded TCR sequences contained amino acid combinations that fit the observed bias. Using these CDR3 sequences as a marker, we traced some of these expansions in the spleen. There, we identified a Vβ22 monoclonal expansion with identical CDR3 sequence to that found in the islets within a polyclonal TCR β-chain variable repertoire. The same Vβ22 TCR was detected in the patient's PBMCs, making a cross talk between the pancreas and spleen that was reflected in peripheral blood evident. No other pancreatic monoclonal expansions were found in peripheral blood or the spleen, suggesting that the Vβ22 clone may have expanded or accumulated in situ by an autoantigen present in both the spleen and pancreas. Thus, the patient's spleen might be contributing to disease perpetuation by expanding or retaining some autoreactive T cells.

Analysis of the peripheral T‐cell repertoire in kidney transplant patients

The long-term stability of renal grafts depends on the absence of chronic rejection. As T cells play a key role in rejection processes, analyzing the T-cell repertoire may be useful for understanding graft function outcomes. We have therefore investigated the power of a new statistical tool, used to analyze the peripheral blood TCR repertoire, for determining immunological differences in a group of 229 stable renal transplant patients undergoing immunosuppression. Despite selecting the patients according to stringent criteria, the patients displayed heterogeneous T-cell repertoire usage, ranging from unbiased to highly selected TCR repertoires; a skewed TCR repertoire correlating with an increase in the CD8(+) /CD4(+) T-cell ratio. T-cell repertoire patterns were compared in patients with clinically opposing outcomes i.e. stable drug-free operationally tolerant recipients and patients with the "suspicious" form of humoral chronic rejection and were found significantly different, from polyclonal to highly selected TCR repertoires, respectively. Moreover, a selected TCR repertoire was found to positively correlate with the Banff score grade. Collectively, these data suggest that TCR repertoire categorization might be included in the calculation of a composite score for the follow-up of patients after kidney transplantation.

Developing NKT cells need their (E) protein

Developing NKT cells need their (E) protein

Chronic Inflammatory Bowel Disease as Key Manifestation of Atypical ARTEMIS Deficiency

We describe a girl presenting at age 6 years with a history of chronic ulcerating intestinal inflammation since 9 months of age. She exhibited a severe, steroid-dependent clinical course of intestinal inflammation over several years in the absence of serious infections. Immunodeficiency was first considered at 6 years of age due to chronic lymphopenia. Immunophenotyping revealed low B and T cell counts with few naïve T cells, a skewed TCR repertoire, and TCR gamma/delta T cell predominance, suggesting a defect of lymphocyte development. Genetic and functional analyses identified a hypomorphic mutation in the DCLRE1C (ARTEMIS) gene compromising V(D)J recombination efficiency, but allowing residual T and B cell development. Hematopoetic stem cell transplantation reconstituted the lymphocyte compartment and cured the inflammatory bowel disease. This report illustrates that a genetic disorder of lymphocyte development can present with chronic inflammatory bowel disease as the dominant phenotype in the absence of severe infection susceptibility.

OP9-DL1 Cell Line Supports the Development of Phenotypically and Functionally Mature Tcrαβ And Tcrγδ T Cells, through Both Conventional and Aberrant Developmental Pathways

In vitro generation of mature T cells from human hematopoietic stem and progenitor cells (HSPC) could fulfill two existing needs. First, it could enhance and quicken T cell immune reconstitution after stem cell transplantation, which is very slow and generates a skewed TCR repertoire. Second, by generation of tumour antigen specific T cells it could provide an efficient therapy for numerous malignancies and could enhance GVT effect in the context of allogeneic SCT, without aggravating GVHD. T cells can be generated from human HSPC by culturing them on the murine stromal cell line OP9-transduced with the Notch ligand Delta-like-1 (OP9-DL1). Notch receptor activation is essential for T cell development. However, it is unclear whether Notch activation is sufficient for end maturation into functionally and phenotypically mature TCR positive cells. It was shown that human CD34+ cells cultured on OP9-DL1 differentiate to T cells which can proliferate and produce interferon-g upon polyclonal stimulation. The nature of the mature cells generated in these cultures, however, has not been well studied. CD34+ HSPC from postnatal thymus (PNT) or cord blood were cocultured with OP9-DL1, in the presence of the cytokines Flt-3L (5 ng/ml), SCF (2.5 ng/ml) and IL-7 (5 ng/ml). Every 3–5 days cells were harvested and transferred to fresh OP9-DL1 cells. At repetitive timepoints, an aliquot of the cells was analysed phenotypically. In some experiments, IL-15 was added to the culture. For some experiments, cells harvested from OP9-DL1 at the timepoint mature T cells were observed (usually about d 40 of culture), were transferred to feeder cells, consisting of JY cell line (5.104 cells/ml irradiated with 50 Gy and PBMC (5.105/ml irradiated with 40 Gy), in the presence of PHA (1 mg/ml). After 7 days, IL-2 (50 IU/ml) was added to the culture. Every 14 days, cells were restimulated with new feeders (irradiated JY and PBMC) and new addition of PHA. After 3 weeks of stimulation cells were stimulated overnight with 15 ng/ml PMA and 1500 ng/ml ionomycin, and 18 hours later cells were checked for intracellular presence of cytokines. We investigated whether the T cell population generated in these cultures contains mature cells with the characteristics of TCRγδ cells and of positively selected CD8 or CD4 single positive (SP) TCRαβ cells as observed in the human thymus. We found that under the described conditions, HSPC mature into CD1-CD27+ phenotypically mature T cells, with the TCRγδ fraction maturing faster and more efficiently compared to the TCRαβ fraction. Consistent with a mature phenotype, TCRγδ cells were mostly CD8αα or double negative (DN). No mature CD4 SP TCRαβ cells were observed and the mature CD8 SP cells co-expressed variable ratios of CD8αβ and CD8αα dimers, suggesting that these cells are not conventional positively selected TCRαβ cells. In support of this hypothesis, both mature CD1- TCRαβ and TCRγδ cells expressed the IL2Rβ receptor consitutively and both populations proliferated on IL-15 without prior antigen stimulation, CD8αα (TCRαβ and TCRγδ) cells being the most IL-15 responsive. Mature activated T cells secreted IFN-γ and TNFα, little or no IL-2 and IL-4, with no difference observed between TCRαβ and TCRγδ cells. These data suggest that CD8 TCRαβ cells generated in these cultures are unconventional CD8 cells possibly maturated through agonist selection. However, when cells harvested after 40 days of culture on OP9-DL1 were stimulated with PHA and IL-2 for 3 weeks, conventional appearing CD8αβ cells emerged, with a cytokine production profile similar to that of thymic CD8αβ TCRαβ T cells, with the majority of cells secreting IFN-γ and IL-2. We can conclude from these data that OP9-DL1 supports the development of both unconventional and conventional CD8+ TCRαβ cells, of which the generation and selection process are currently being investigated. Also the in vitro anti-tumor capacities of both populations need to be addressed.

Human TCR α/β+ CD4−CD8− Double-Negative T Cells in Patients with Autoimmune Lymphoproliferative Syndrome Express Restricted Vβ TCR Diversity and Are Clonally Related to CD8+ T Cells

The peripheral expansion of alpha/beta+-CD4-CD8- double negative (DN) T cells in patients with autoimmune lymphoproliferative syndrome (ALPS) is a consistent feature of this disease, and part of the diagnostic criteria of ALPS. The origin of these cells remains undetermined. They could derive from mature T cells that have lost coreceptor expression, or represent a special minor cell lineage. To investigate relationship of DN and single positive (SP) T cells in ALPS, we used Immunoscope technology to analyze the TCRVbeta repertoire diversity of sorted DN and SP T cells, and we performed CDR3 sequence analyses of matching clonotypes. We show that DN T cells express all the Vbeta gene families that are used by their SP counterparts, though they dominantly use some Vbeta genes. Analysis of CDR3 length distribution revealed a diverse polyclonal TCR repertoire for sorted CD4+ T cells, whereas both DN and CD8+ T cells showed a skewed TCR repertoire with oligoclonal expansions throughout most of the Vbeta families. CDR3 sequencing of matching clonotypes revealed a significant sharing of CDR3 sequences from selected Vbeta-Jbeta transcripts between DN and CD8+ T cells. Altogether, these data strongly argue for a CD8 origin of DN T cells in ALPS.

Maintenance of memory CD8+ T cell diversity and proliferative potential by a primary response upon re-challenge

Memory CD8+ T cells generated during an immune response are long lived and self-renewing, offering enhanced host protection against re-infection. However, how an antigen-specific population of memory T cells is maintained, throughout repetitive infections over potentially a lifetime, is not known. Here we show that a primary response during re-challenge significantly contributes to memory T cell pool both qualitatively and quantitatively. Upon re-challenge, the skewed Vbeta usage and TCR repertoire of pre-existing memory T cells is partly corrected by diversity in a newly primed (primary) T cell population. Importantly, this primary population expands more vigorously in a subsequent antigen encounter. These findings indicate that memory T cell populations evolve over multiple challenges, favoring memory T cells generated in more recent encounters, and suggest that these primary populations have essential roles in the perpetuation of antigen-specific T cell populations.

Skewed TCR Repertoire of Vδ1+ γδT Cells in Recipients of Allogeneic Hematopoietic Stem Cell Grafts and Possible Involvement of Epstein-Barr Virus in Clonal Expansion of Vδ1+ T Cells.

Background: We previously demonstrated that stable clonal expansion of Vδ1+ γδT lymphocytes persisted for several years after human allogeneic hematopoietic stem cell transplantation (allo-HSCT). These Vδ1+ T cells are derived from mature T cells in the graft. In the present study, we have extended our observation to learn whether oligoclonal expansions of Vδ1+ γδT lymphocytes might be associated with clinical outcome and GVHD, and whether consensus sequences of the CDR3 region of clonally expanded Vδ1+ T cells would be observed among different individuals. We also examined the possible role for Epstein-Barr virus (EBV) in clonal expansion of Vδ1+ T cells.Methods: Forty-two patients receiving allo-HSCT for hematological malignancies were included in this study. Grafts included bone marrow (n=33), G-CSF mobilized peripheral blood stem cells (n=7) and cord blood (n=2). Clonality of the Vδ1+ T cell subset was determined by CDR3 size spectratyping analysis. Junctional sequences were determined by DNA sequencing. In some experiments, PBMCs from healthy volunteer donors were stimulated with autologous EBV-LCL and were analyzed for clonality of TCRs.Results: CDR3 size spectratyping analysis revealed that twenty-three out of forty-two patients had highly skewed TCR repertoires of the Vδ1+ T cells. There was no apparent association between the oligoclonality of Vδ1+ TCRs and clinical outcome such as GVHD and leukemia relapse. In eight out of seventeen patients examined, the -WGI- amino acid sequence was observed in the CDR3 region of TCRs of clonally expanded Vδ1+ T cells. The -YWG- sequence was observed in four patients. All recipients examined were serologically positive for EBV-VCA IgG and EBNA. Bacterial or fungal components failed to stimulate Vδ1+ T cells to proliferate in vitro, but autologous EBV transformed B cells could induce the expansion of Vδ1+ T cells. The CDR3 size distribution patterns of Vδ1+ TCRs became skewed after stimulation with autologous EBV-LCL, and the T cell clone with the -LEEYWGLPH- CDR3 sequence predominated in the culture with autologous EBV-LCL, whereas this clone was not detectable before culture. Moreover, allogeneic EBV-positive Raji cells also induced the oligoclonal expansion of Vδ1+ T cells carrying the -WGI- or -YWG- junctional sequence. These results suggest the CDR3 structure may contribute to recognition of EBV-associated antigens by Vδ1+ T cellsConclusion: Skewing of the Vδ1+ TCR after allo-HSCT may be the result of the response to infectious antigens widely existing in humans such as EBV.Table 1. Junctional diversity of Vδ1 TCR of γδ T cells expanded in response to autologous EBV-LCL and allogeneic Burkitt lymphoma cellsStimulationδV1N-D-NJδColony frequencyNilCALGEGLPHALIMWGDLAYTDKLIFGKG3/20EBV-LCLCALGELEEYWGLPHTDKLIFGKG10/27CALGEGLPHALIMWGDLAYTDKLIFGKG7/27CALGGVLYWGIRRTDKLIFGKG2/27CALGESLWGIRYTDKLIFGKG2/27CALGELGETTPLLGGYSFALTAQLFFGKG2/27RajiCALGVSGLARGGSLKLIFGKG6/25CALGEADWGIRARILYTDKLIFGKG4/25CALGEPRAILGDTRIKRMYTDKLIFGKG4/25CALGELEEYWGLPHTDKLIFGKG3/25CALGEDPGLPFLWYTDKLIFGKG2/25CALGDLNLLWGIRSILPGTDKLIFGKG2/25T cell clones appearing more than once are presented.

Identification of the T cell clones expanding within both CD8(+)CD28(+) and CD8(+)CD28(-) T cell subsets in recipients of allogeneic hematopoietic cell grafts and its implication in post-transplant skewing of T cell receptor repertoire.

We have previously reported that skewed repertoires of T cell receptor-beta chain variable region (TCRBV) and TCR-alpha chain variable region (TCRAV) are observed at an early period after allogeneic hematopoietic cell transplantation. Furthermore, we found that T lymphocytes using TCRBV24S1 were increased in 28% of the recipients of allogeneic grafts and an increase of TCRBV24S1 usage was shown to result from clonal expansions. Interestingly, the arginine residue was frequently present at the 3' terminal of BV24S1 segment and was followed by an acidic amino acid residue within the CDR3 region. These results suggest that these clonally expanded T cells are not randomly selected, but are expanded by stimulation with specific antigens. This study was undertaken to elucidate the mechanisms of the post-transplant skewing of TCR repertoires. Since the CD8(+)CD28(-)CD57(+) T cell subset has been reported to expand in the peripheral blood of patients receiving allogeneic hematopoietic cell grafts, we examined the TCRAV and TCRBV repertoires of the CD8(+)CD28(-) T cell and CD8(+)CD28(+) T cell subsets, and also determined the clonality of both T cell populations. In all three recipients examined, the CD8(+)CD28(-) T cell subset appeared to define the post-transplant TCR repertoire of circulating blood T cells. Moreover, the CDR3 length of TCRBV imposed constraints in both CD8(+)CD28(-) T cell and CD8(+)CD28(+) T cell subsets. The DNA sequences of the CDR3 region were determined, and the same clones were identified within both CD8(+)CD28(-) and CD8(+)CD28(+) T cell subsets in the same individuals. These results suggest that the clonally expanded CD8(+)CD28(-) T cells after allogeneic hematopoietic cell transplantation derive from the CD8(+)CD28(+) T cell subset, possibly by an antigen-driven mechanism, resulting in the skewed TCR repertoire.

Biased TCR Repertoire in HIV-1-Infected Patients Due to Clonal Expansion of HIV-1-Reverse Transcriptase-Specific CTL Clones

To study whether an expansion of HIV-1-specific CTL is contributing to the skewed TCR repertoire in HIV-1-infection, we characterized the TCR usage of CTL clones specific for a conserved epitope in HIV-1 reverse transcriptase (RT/476-484). CTL clones from three HIV-1-infected patients displayed highly similar TCR usage and used the identical Vbeta6.1 and Valpha2.5 gene segments. CTL clones from two patients showed a very high degree of similarity within the TCR complementarity-determining region-3 (CDR-3). In accordance with the similar molecular structure, all three CTL clones also exhibited a similar functional activity with regard to recognition of variant peptides and cytokine secretion pattern. In one subject clonal expansion of a single CTL specificity could be shown over a 10-mo period. TCR spectratyping of PBMC from two patients revealed a marked expansion of CDR-3 segments of a certain length within the Vbeta6-family. Sequence analysis of these CDR-3 yielded sequences identical to the RT/476-484-specific CTL previously isolated from the same patients. This analysis demonstrates that clonal expansion of HIV-1-specific CTL is contributing to the skewed TCR repertoire in HIV-1-infected patients.

Absolute requirement for the pre-T cell receptor alpha chain during NK1.1+ TCRalphabeta cell development.

Most natural killer T (NKT) cells express a highly skewed alphabeta TCR repertoire, consisting of an invariant V alpha14-J alpha281 chain paired preferentially with a polyclonal Vbeta8.2 chain. This repertoire is positively selected by the monomorphic CD1d molecule expressed on cells of hematopoietic origin. The origin of NKT cells and their lineage relationship to conventional T cells is controversial. We show here that the development of NKT cells is absolutely dependent on expression of the pre-TCRalpha chain, in marked contrast to conventional T cells which arise in significant numbers even in the absence of a functional pre-TCR. Distinct developmental requirements for pre-TCR expression in the NKT and T cell lineages may reflect differences in the ability of the TCRalphabeta to substitute functionally for the pre-TCR in immature precursor cells.

Expression of an ovalbumin-specific V beta 8.2 TCR transgene inhibits collagen arthritis in B10.Q mice.

Previous studies have illustrated the importance of T cells bearing alpha beta TCRs in the induction and development of collagen induced arthritis (CIA) in mice. However, the scope of TCR usage in CIA has yet to be clearly defined. Given the inherent diversity of the TCR repertoire, the relative flexibility of the arthritogenic TCR repertoire specific for type II collagen (CII) is not clear. Therefore, we chose to examine the influence of a highly skewed TCR repertoire on CIA. Arthritis susceptible B10.Q (H-2q) mice were mated with C57L (H-2b) animals expressing an ovalbumin-specific V beta 8.2 TCR transgene (Tg) and Tg+ offspring were further backcrossed to B10.Q. Homozygous H-2q/q, V beta 8.2 Tg+ mice displayed a high level of V beta 8.2+ T cells in peripheral blood. However, expression of some endogenous V beta TCR, such as V beta 14, was still detected. Upon immunization with bovine CII in adjuvant, V beta 8.2 Tg+ mice were highly resistant to CIA when compared with Tg- littermates. Analysis of sera demonstrated a marked reduction in antibody specific for homologous mouse CII as well as heterologous bovine CII in Tg+ animals. Interestingly, V beta 8.2 Tg+ mice still mounted good antibody responses following immunization with human thyroglobulin, indicating that the skewed TCR repertoire affected anti-CII but not antithyroglobulin responses. Thus, our findings show that constraints placed on the TCR repertoire inhibit pathogenic responses against CII and suggest that in H-2q mice the arthritogenic TCR repertoire bears only limited flexibility.

The fate of CD4-8- T cell receptor-alpha beta+ thymocytes.

CD4-8- TCR-alpha beta+ thymocytes represent a distinct population whose fate and function have remained a mystery. We show here that this thymocyte subset bears NK1, a surface Ag previously thought to be expressed exclusively by TCR- NK cells. Analysis of peripheral lymphocytes for the coexpression of TCR-alpha beta and NK1 revealed a subset with similar characteristics to the NK1+ thymocytes: a large fraction that are CD4-8- and a skewed TCR repertoire in which V beta 8 is overrepresented. Thymus transplant experiments into congenically marked athymic (nude) mice revealed that the NK1+TCR alpha beta+ subset was exclusively thymus derived and represented a distinct subset from the thymus-independent NK1+TCR- population. Finally, the NK1+TCR alpha beta+ population preferentially localizes to the bone marrow. These results demonstrate that this T cell subset is exported to the periphery after developing in the thymus. Their unique surface Ag expression and tissue localization suggest an immune function distinct from classical T cells.