Altered T-cell Receptor Research Articles

Comparison of T-cell receptor diversity of people with myalgic encephalomyelitis versus controls

ObjectiveMyalgic Encephalomyelitis (ME; sometimes referred to as Chronic Fatigue Syndrome) is a chronic disease without laboratory test, detailed aetiological understanding or effective therapy. Its symptoms are diverse, but it is distinguished from other fatiguing illnesses by the experience of post-exertional malaise, the worsening of symptoms even after minor physical or mental exertion. Its frequent onset after infection suggests autoimmune involvement or that it arises from abnormal T-cell activation.ResultsTo test this hypothesis, we sequenced the genomic loci of α/δ, β and γ T-cell receptors (TCR) from 40 human blood samples from each of four groups: severely affected people with ME; mildly or moderately affected people with ME; people diagnosed with Multiple Sclerosis, as disease controls; and, healthy controls. Seeking to automatically classify these individuals’ samples by their TCR repertoires, we applied P-SVM, a machine learning method. However, despite working well on a simulated data set, this approach did not allow statistically significant partitioning of samples into the four subgroups. Our findings do not support the hypothesis that blood samples from people with ME frequently contain altered T-cell receptor diversity.

Altered T-cell receptor β repertoire in adults with SARS CoV-2 inactivated vaccine of BBIBP-CorV

ObjectiveSevere acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused the prolonged and widespread epidemic of coronavirus disease 2019 (COVID-19). The inactivated BBIBP-CorV vaccine has shown safety, efficacy and immunogenicity against COVID-19 in in-vitro studies and clinical trials. However, the characteristics changes of the TCRβ repertoire in patients receiving BBIBP-CorV remain unclear. MethodsTCRβ repertoire difference were analyzed between 54 uninfected subjects who received a third dose of the enhanced BBIBP-CorV vaccine and the 16 healthy donors who did not receive the vaccine and 44 COVID-19 patients with different courses of disease (asymptomatic, symptomatic and convalescent). Furthermore, antibody response, anti-inflammatory and pro-inflammatory cytokines also were examined. ResultsWe found that the third dose inactivated coronavirus vaccine induced widespread changes including the increased TCRβ repertoire diversity, a much shorter CDR3 length and high usage of V-J genes segments. Meanwhile, the vaccine-responding clones were also predicted. The results of the antibody response showed that 90.7 % of the vaccinated individuals were positive for NAb seroconversion and 88.9 % for IgG antibody about 60 days after the third dose. The concentration of IL-2 increased significantly compared to baseline inoculation. ConclusionAltered TCRβ repertoire in adults with SARS CoV-2 inactivated vaccine of BBIBP-CorV clarified the specific immunity induced by inactivated vaccines. Our research provides insights into the adaptive immune response induced by the new inactivated SARS-CoV-2 vaccine and strengthens the development of immunotherapy.

The Wiskott-Aldrich syndrome protein is required for positive selection during T-cell lineage differentiation.

The Wiskott-Aldrich syndrome (WAS) is an X-linked primary immune deficiency caused by a mutation in the WAS gene. This leads to altered or absent WAS protein (WASp) expression and function resulting in thrombocytopenia, eczema, recurrent infections, and autoimmunity. In T cells, WASp is required for immune synapse formation. Patients with WAS show reduced numbers of peripheral blood T lymphocytes and an altered T-cell receptor repertoire. In vitro, their peripheral T cells show decreased proliferation and cytokine production upon aCD3/aCD28 stimulation. It is unclear whether these T-cell defects are acquired during peripheral activation or are, in part, generated during thymic development. Here, we assessed the role of WASp during T-cell differentiation using artificial thymic organoid cultures and in the thymus of humanized mice. Although CRISPR/Cas9 WAS knockout hematopoietic stem and progenitor cells (HSPCs) rearranged the T-cell receptor and differentiated to T-cell receptor (TCR)+ CD4+ CD8+ double-positive (DP) cells similar to wild-type HSPCs, a partial defect in the generation of CD8 single-positive (SP) cells was observed, suggesting that WASp is involved in their positive selection. TCR repertoire analysis of the DP and CD8+ SP population, however, showed a polyclonal repertoire with no bias toward autoreactivity. To our knowledge, this is the first study of the role of WASp in human T-cell differentiation and on TCR repertoire generation.

Hypersensitivity reactions to small molecule drugs.

Drug hypersensitivity reactions induced by small molecule drugs encompass a broad spectrum of adverse drug reactions with heterogeneous clinical presentations and mechanisms. These reactions are classified into allergic drug hypersensitivity reactions and non-allergic drug hypersensitivity reactions. At present, the hapten theory, pharmacological interaction with immune receptors (p-i) concept, altered peptide repertoire model, and altered T-cell receptor (TCR) repertoire model have been proposed to explain how small molecule drugs or their metabolites induce allergic drug hypersensitivity reactions. Meanwhile, direct activation of mast cells, provoking the complement system, stimulating or inhibiting inflammatory reaction-related enzymes, accumulating bradykinin, and/or triggering vascular hyperpermeability are considered as the main factors causing non-allergic drug hypersensitivity reactions. To date, many investigations have been performed to explore the underlying mechanisms involved in drug hypersensitivity reactions and to search for predictive and preventive methods in both clinical and non-clinical trials. However, validated methods for predicting and diagnosing hypersensitivity reactions to small molecule drugs and deeper insight into the relevant underlying mechanisms are still limited.

Homologous recombination repair deficient prostate cancer represents an immunologically distinct subtype

ABSTRACT Homologous recombination repair deficiency (HRD) is observed in 10% of patients with castrate-resistant prostate cancer (PCa). Preliminary data suggest that HRD-PCa might be more responsive to immune checkpoint inhibitors (ICIs). In this study, we compare the tumor immune landscape and peripheral T cell receptor (TCR) repertoire of patients with and without HRD-PCa to gain further insight into the immunogenicity of HRD-PCa. Immunohistochemistry was performed on tumor tissue of 81 patients, including 15 patients with HRD-PCa. Peripheral TCR sequencing was performed in a partially overlapping cohort of 48 patients, including 16 patients with HRD-PCa. HRD patients more frequently had intratumoral CD3+, CD3+CD8−FoxP3− or Foxp3+ TILs above median compared to patients without DNA damage repair alterations (DDRwt; CD3+ and Foxp3+: 77% vs 35%, p = .013; CD3+CD8−FoxP3−: 80% vs 44%, p = .031). No significant difference in CD8+ TILs or PD-L1 expression was observed. In peripheral blood, HRD patients displayed a more diverse TCR repertoire compared to DDRwt patients (p = .014). Additionally, HRD patients shared TCR clusters with low generation probability, suggesting patient-overlapping T cell responses. A pooled analysis of clinical data from 227 patients with molecularly characterized PCa suggested increased efficacy of ICIs in HRD-PCa. In conclusion, patients with HRD-PCa display increased TIL density and an altered peripheral TCR repertoire. Further research into the efficacy of ICIs and the presence of shared neoantigens in HRD-PCa is warranted.

1268-P: Underlying T Cell Receptor Methylation Defects in Type 1 Diabetes Associated with Quantitative Defects

The T cell receptor (TCR) is a central regulator of the adaptive immune system. Efficient structural organization and signaling of TCR/CD3 underlies the development and function of T cells. T cell maturation defects are associated with autoimmunity, suggesting an underlying defect in TCR selection. To explore quantitative defects as a cause for altered TCR selection at the level of the TCR/CD3 protein complex, we compared TCR expression densities on CD4 T cells from subjects with type 1 diabetes (T1D) (n=80) and nondiabetes controls (n=37) . We also investigated a quantitative defect in genes in the TCR/CD3 genome for possible underlying overmethylation in T1D. All 13 gene regions of the TCR segments and all 4 versions of CD3 proteins were studied for methylation and protein differences in T1D vs. controls. Significant quantitative defects in TCR and CD3 proteins were observed in CD4+ T cells of patients with T1D vs. controls. As a cause for these defects, the TCR complex genes and associated CD3 genes were overmethylated, resulting in downregulated cell surface expression. Evaluation of TCRαβ expression in CD4+ T cells at the protein level confirmed methylation patterns, showing that the population of TCRαβ+ cells was significantly reduced in T1D vs. controls (p=0.005) . The MFI density of TCRαβ antibody in T1D was also significantly decreased vs. controls (p=0.01) . All CD3 genes except CD3ε had hypermethylated patterns in T1D, confirmed by RNAseq analysis. The percentage CD3+ T cells in the CD4+ T cell population was reduced in T1D vs. controls (p=0.04) , as was the MFI of CD3+ T cells (p=0.02) . Patients with T1D have quantitative defects in the TCR/CD3 protein complex, resulting in decreased expression. It is recognized that TCR triggering is affected by intermolecular distance between TCR proteins and that activation diminishes when proximity is increased between TCR surface proteins. In T1D, this might be a novel mechanism for failed T cell selection leading to autoimmunity. Disclosure W.Kuhtreiber: None. A.H.Lee: None. A.Aristarkhova: None. H.F.Dias: None. N.Ng: None. S.A.Bien: Employee; Adaptive Biotechnologies. D.L.Faustman: None.

Altered T-Cell Receptor β-Chain and Lactate Dehydrogenase Are Associated With the Immune Pathogenesis of Biliary Atresia.

Background: Biliary atresia (BA) is considered to be an autoimmune-mediating inflammatory injury. The pathogenesis of BA has been proposed with the clonal transformation of T cells expressing analogous T-cell receptor β-chain variable regions (TRBVs).Methods: The TRBV profile of the peripheral blood mononuclear cells (PBMCs) in infants with BA and control infants (healthy donors, HDs), respectively, were characterized by using high-throughput sequencing (HTS). The diversity of T cells was analyzed based on the frequency of complementarity-determining region 3 (CDR3) or V(CDR3)J. Moreover, the correlation between absolute lymphocyte count (ALC) and lactate dehydrogenase (LDH) or diversity (clonality) indices, respectively, were analyzed for subjects with BA and HD.Results: The diversity indices of CDR3, V(CDR3)J in BA are lower than those in subjects with HD, in addition, there are significantly different levels of neutrophile, neutrophile/lymphocyte ratio (NLR), and LDH between groups of BA and HD. The correlation between ALC and diversity index is significant in subjects with HD but is not for subjects with BA. Conversely, the relationship between ALC and LDH is significant in subjects with BA but is not for subjects with HD. Moreover, 12 CDR3 motifs are deficient or lower expression in BA compared with that in the HD group.Conclusion: Our results demonstrate that the profile of TRBV repertoire is significantly different between subjects with BA and HD, and suggest that the immune imbalance and elevated LDH level are associated with the pathogenesis of BA. Moreover, the values of neutrophile, NLR, and LDH could be used for the differential diagnosis of BA.

MutT Homolog 1 Inhibitor Karonudib Attenuates Autoimmune Hepatitis by Inhibiting DNA Repair in Activated T Cells.

Autoimmune hepatitis (AIH) is an inflammatory liver disease driven by the hyperactivation of various intrahepatic antigen‐specific T cells due to a breach of immune tolerance. Studies in immunometabolism demonstrate that activated T cells harbor increased levels of reactive oxygen species that cause oxidative DNA damage. In this study, we assessed the potential of DNA damage repair enzyme MutT homolog 1 (MTH1) as a therapeutic target in AIH and karonudib as a novel drug for patients with AIH. We report herein that MTH1 expression was significantly increased in liver samples from patients with AIH compared to patients with chronic hepatitis B and nonalcoholic fatty liver disease and from healthy controls. In addition, the expression of MTH1 was positively correlated with AIH disease severity. We further found abundant T cells that expressed MTH1 in AIH. Next, we found that karonudib significantly altered T‐cell receptor signaling in human T cells and robustly inhibited proliferation of human T cells in vitro. Interestingly, our data reflected a preferential inhibition of DNA damage repair in activated T cells by karonudib. Moreover, MTH1 was required to develop liver inflammation and damage because specific deletion of MTH1 in T cells ameliorated liver injury in the concanavalin A (Con A)‐induced hepatitis model by inhibiting T‐cell activation and proliferation. Lastly, we validated the protective effect of karonudib on the Con A‐induced hepatitis model. Conclusion: MTH1 functions as a critical regulator in the development of AIH, and its inhibition in activated T cells reduces liver inflammation and damage.

Influenza A virus-induced thymus atrophy differentially affects dynamics of conventional and regulatory T-cell development in mice.

Foxp3+ Treg cells, which are crucial for maintenance of self-tolerance, mainly develop within the thymus, where they arise from CD25+ Foxp3- or CD25- Foxp3+ Treg cell precursors. Although it is known that infections can cause transient thymic involution, the impact of infection-induced thymus atrophy on thymic Treg (tTreg) cell development is unknown. Here, we infected mice with influenzaA virus (IAV) and studied thymocyte population dynamics post infection. IAV infection caused a massive, but transient thymic involution, dominated by a loss of CD4+ CD8+ double-positive (DP) thymocytes, which was accompanied by a significant increase in the frequency of CD25+ Foxp3+ tTreg cells. Differential apoptosis susceptibility could be experimentally excluded as a reason for the relative tTreg cell increase, and mathematical modeling suggested that enhanced tTreg cell generation cannot explain the increased frequency of tTreg cells. Yet, an increased death of DP thymocytes and augmented exit of single-positive (SP) thymocytes was suggested to be causative. Interestingly, IAV-induced thymus atrophy resulted in a significantly reduced T-cell receptor (TCR) repertoire diversity of newly produced tTreg cells. Taken together, IAV-induced thymus atrophy is substantially altering the dynamics of major thymocyte populations, finally resulting in a relative increase of tTreg cells with an altered TCR repertoire.

Extensive proteomic and transcriptomic changes quench the TCR/CD3 activation signal of latently HIV-1 infected T cells.

The biomolecular mechanisms controlling latent HIV-1 infection, despite their importance for the development of a cure for HIV-1 infection, are only partially understood. For example, ex vivo studies have recently shown that T cell activation only triggered HIV-1 reactivation in a fraction of the latently infected CD4+ T cell reservoir, but the molecular biology of this phenomenon is unclear. We demonstrate that HIV-1 infection of primary T cells and T cell lines indeed generates a substantial amount of T cell receptor (TCR)/CD3 activation-inert latently infected T cells. RNA-level analysis identified extensive transcriptomic differences between uninfected, TCR/CD3 activation-responsive and -inert T cells, but did not reveal a gene expression signature that could functionally explain TCR/CD3 signaling inertness. Network analysis suggested a largely stochastic nature of these gene expression changes (transcriptomic noise), raising the possibility that widespread gene dysregulation could provide a reactivation threshold by impairing overall signal transduction efficacy. Indeed, compounds that are known to induce genetic noise, such as HDAC inhibitors impeded the ability of TCR/CD3 activation to trigger HIV-1 reactivation. Unlike for transcriptomic data, pathway enrichment analysis based on phospho-proteomic data directly identified an altered TCR signaling motif. Network analysis of this data set identified drug targets that would promote TCR/CD3-mediated HIV-1 reactivation in the fraction of otherwise TCR/CD3-reactivation inert latently HIV-1 infected T cells, regardless of whether the latency models were based on T cell lines or primary T cells. The data emphasize that latent HIV-1 infection is largely the result of extensive, stable biomolecular changes to the signaling network of the host T cells harboring latent HIV-1 infection events. In extension, the data imply that therapeutic restoration of host cell responsiveness prior to the use of any activating stimulus will likely have to be an element of future HIV-1 cure therapies.

Abstract B060: Commensal bacteria Bifidobacterium stimulates an antitumor response via cross-reactivity

Abstract While recent studies have shown an important role of the microbiome in modulating anti-tumor immune responses, its mechanism remains unclear. One proposed mechanism is due to cross-reactivity between antigens expressed in commensal bacteria and neoepitopes found in tumors. We have identified a cross-reactive antigen expressed in commensal bacteria Bifidobacterium (Bifido.) “SVYRYYGL” (henceforth called SVY) and show that it conveys a neoantigen-specific cross-reactivity to the classic neoantigen “SIY.” The SVY-specific response was analyzed through biophysical experiments and molecular dynamics simulations, which showed that the SVY peptide bound the H2-Kb MHC (Kb) with an altered peptide configuration leading to a cross-reactivity but at a lower overall affinity for the transgenic, SIY-specific 2C T-cell receptor (TCR). By T-cell expansion studies, commensal bacteria SVY-specific T-cells populations have a cross-reactive SIY specific T-cell response and those T-cell populations can recognize tumors expressing the “SIY” antigen. Mice lacking Bifido. have a decreased commensal bacteria specific T-cell response and an altered TCR repertoire compared to Bifido. colonized animals. Moreover, Bifido. colonization not only shapes the SVY commensal bacteria-specific T-cell repertoire but selects for clones that are represented in the SIY T-cell repertoire. Cross-reactive SVY-specific T-cells recognize tumors bearing SIY in vivo in an adoptive T-cell transfer model and a murine melanoma model. Animals treated with cross-reactive SVY-specific T-cells had decreased tumor growth and extended survival. Our work demonstrates that commensal bacteria can directly stimulate antitumor immune responses via T-cell cross-reactivity and provides a proof of principle for how bacterial antigens can shape the T-cell landscape. Citation Format: Catherine Ami Bessell. Commensal bacteria Bifidobacterium stimulates an antitumor response via cross-reactivity [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr B060.

FcγRIIIa-Syk Co-signal Modulates CD4+ T-cell Response and Up-regulates Toll-like Receptor (TLR) Expression

CD4(+) T-cells in systemic lupus erythematosus (SLE) patients show altered T-cell receptor signaling, which utilizes Fc-receptor γ-chain FcRγ-Syk. A role for FcγRIIIa activation from immune complex (IC) ligation and sublytic terminal complement complex (C5b-9) in CD4(+) T-cell responses is not investigated. In this study, we show that the ICs present in SLE patients by ligating to FcγRIIIa on CD4(+) T-cells phosphorylate Syk and provide a co-stimulatory signal to CD4(+) T-cells in the absence of CD28 signal. This led to the development of pathogenic IL-17A(+) and IFN-γ(high) CD4(+) T-cells in vitro. Cytokines IL-1β, IL-6, TGF-β1, and IL-23 were the only requirement for the development of both populations. SLE patients CD4(+) T-cells that expressed CD25, CD69, and CD98 bound to ICs showed pSyk and produced IFN-γ and IL-17A. This FcγRIIIa-mediated co-signal differentially up-regulated the expression of IFN pathway genes compared with CD28 co-signal. FcγRIIIa-pSyk up-regulated several toll-like receptor genes as well as the HMGB1 and MyD88 gene transcripts. ICs co-localized with these toll-like receptor pathway proteins. These results suggest a role for the FcγRIIIa-pSyk signal in modulating adaptive immune responses.

Oligoclonal CD8+ T cells play a critical role in the development of hypertension.

Recent studies have emphasized a role of adaptive immunity, and particularly T cells, in the genesis of hypertension. We sought to determine the T-cell subtypes that contribute to hypertension and renal inflammation in angiotensin II-induced hypertension. Using T-cell receptor spectratyping to examine T-cell receptor usage, we demonstrated that CD8(+) cells, but not CD4(+) cells, in the kidney exhibited altered T-cell receptor transcript lengths in Vβ3, 8.1, and 17 families in response to angiotensin II-induced hypertension. Clonality was not observed in other organs. The hypertension caused by angiotensin II in CD4(-/-) and MHCII(-/-) mice was similar to that observed in wild-type mice, whereas CD8(-/-) mice and OT1xRAG-1(-/-) mice, which have only 1 T-cell receptor, exhibited a blunted hypertensive response to angiotensin II. Adoptive transfer of pan T cells and CD8(+) T cells but not CD4(+)/CD25(-) cells conferred hypertension to RAG-1(-/-) mice. In contrast, transfer of CD4(+)/CD25(+) cells to wild-type mice receiving angiotensin II decreased blood pressure. Mice treated with angiotensin II exhibited increased numbers of kidney CD4(+) and CD8(+) T cells. In response to a sodium/volume challenge, wild-type and CD4(-/-) mice infused with angiotensin II retained water and sodium, whereas CD8(-/-) mice did not. CD8(-/-) mice were also protected against angiotensin-induced endothelial dysfunction and vascular remodeling in the kidney. These data suggest that in the development of hypertension, an oligoclonal population of CD8(+) cells accumulates in the kidney and likely contributes to hypertension by contributing to sodium and volume retention and vascular rarefaction.

Altered T-cell receptor signaling in the pathogenesis of allergic disease

Mounting evidence from animal models has demonstrated that alterations in T-cell receptor (TCR) signaling alone can lead to dramatically skewed differentiation of naive T cells into T(H)2 cells, to T(H)2 effector functions, and to T(H)2-related diseases. There is significant potential relevance of these observations to human disease. Specifically, a number of immunodeficiencies associated with atopic disease might have atopy as a manifestation because of aberrant TCR signaling. It is therefore important to attempt to identify a role for defects in TCR signaling in the pathogenesis of common atopic diseases.

T-cell receptor signals direct the composition and function of the memory CD8+ T-cell pool

AbstractSH2 domain-containing leukocyte phosphoprotein of 76 kDa (SLP-76) nucleates a signaling complex critical for T-cell receptor (TCR) signal propagation. Mutations in the tyrosines of SLP-76 result in graded defects in TCR-induced signals depending on the tyrosine(s) affected. Here we use 2 strains of genomic knock-in mice expressing tyrosine to phenylalanine mutations to examine the role of TCR signals in the differentiation of effector and memory CD8+ T cells in response to infection in vivo. Our data support a model in which altered TCR signals can determine the rate of memory versus effector cell differentiation independent of initial T-cell expansion. Furthermore, we show that TCR signals sufficient to promote CD8+ T-cell differentiation are different from those required to elicit inflammatory cytokine production.

Natural viral suppressors of HIV-1 have a unique capacity to maintain γδ T cells

To evaluate Vgamma2Vdelta2 T cells in a group of HIV-infected patients who suppress HIV replication without antiretroviral therapy (natural viral suppressors, NVSs). : It is a cross-sectional study. We compared Vgamma2Vdelta2 T-cell frequency, T-cell repertoire, and responses to isopentenyl pyrophosphate stimulation between NVSs (n = 21) and HIV-uninfected controls (n = 27) and between NVSs and HIV-infected patients taking HAART with suppressed viral replication (HIV-P; n = 25). NVSs had a mean frequency of 1.06 +/- 0.82% CD3Vdelta2+ cells among total lymphocytes, which was significantly higher than both control groups (HIV-negative: 0.50 +/- 0.53%, P = 0.042; HIV-P: 0.34 +/- 0.37%, P = 0.002). The proportion of Vgamma2 chains correlating with the Vgamma2-Jgamma1.2 rearrangement was reduced among NVSs compared with HIV-negative controls (0.57 +/- 0.06 vs. 0.32 +/- 0.04; P = 0.016) but was increased compared with HIV-P patients (0.32 +/- 0.04 vs. 0.22 +/- 0.03; P = 0.03). NVSs had a similar baseline frequency of CD27/CD45RA effector cells (19.6 +/- 4.2%) compared with HIV-negative controls (20.8 +/- 12.9%; P = 0.35). The altered gammadelta T-cell receptor repertoire among NVS was consistent with the known effect of HIV-1 on these cells. Uniquely among all HIV-infected groups, NVS reconstituted the gammadelta T-cell population, eventually reaching levels significantly above controls. This capacity to recover gammadelta T-cell numbers and function distinguishes individuals who control HIV-1 with and without HAART.

Immune system derived from homeostatic proliferation generates normal CD8 T-cell memory but altered repertoires and diminished heterologous immune responses

AbstractThe host responds to lymphopenic environments by acute homeostatic proliferation of T lymphocytes, which acquire phenotypes similar to memory cells. Using T-cell knockout (KO) mice adoptively reconstituted with splenocytes from immunologically naive mice, we examined the immune responses of an immune system derived from homeostatically proliferating (HP) T cells. HP cells mounted relatively normal acute CD8 T-cell responses to lymphocytic choriomeningitis virus (LCMV), but with altered T-cell receptor (TCR) repertoires, and they became functional memory cells capable of recall responses. Although homeostatic proliferation does not normally fully restore T-cell numbers, the CD8+ T-cell pool was completely restored in T-cell KO mice after LCMV infection. CD4 T-cell responses were lower and not fully restored but seemed sufficient to allow for complete differentiation of CD8 memory T cells. The LCMV-immune HP mouse had an immune repertoire heavily biased with LCMV epitope-specific T cells with oligoclonal expansions. LCMV-immune HP mice had reduced cross-reactive and non–cross-reactive CD8 T-cell responses when challenged with a T cell–cross-reactive virus. Thus, whereas an HP immune system is capable of mounting relatively normal acute and memory CD8 T-cell responses, the narrowing of the T-cell repertoire may reduce immune responses to subsequently encountered pathogens.

Individual Response to Low Dose Radiation Exposure as Determined by TCR Assay

The aim of the work was to study the level of somatic gene mutagenesis in various human contingents exposed to ionizing radiation at doses up to 200 mSv. Flow cytometry was used to determine frequency of variant CD4+ T-lymphocytes with altered T-cell receptor (TCR) /CD3 expression as result of mutations at TCR locus. The TCR-mutant cell frequency was assessed in 250 unexposed control donors and 1198 exposed persons, including employees of Nuclear Power Engineering (mean dose (±SE) 100,0±6,6 MSv was accumulated within 27,4±1,1 years), cleanup workers of the Chernobyl accident (mean dose 100,0±9,1 MGy, analysis was performed 9-19 years after the irradiation) and persons living in radiation contaminated areas (137 Cs density 37- 555 kBq/m2 ) during 15-19 years. Results of group analysis demonstrated an increase in frequency of the TCR-mutant cells in NPE employees and the Chernobyl cleanup workers compared to that in age-matched control groups (p Cs density over 100 kBq/m2 in comparison to less contaminated areas: 14,5% vs 8,8% accordingly (p=0,02, Fisher’s test). In conclusion, relatively small proportion of persons was found to react to low dose radiation exposure by elevation of the TCR-mutant cell frequency in all groups excluding irradiation in utero. The work was supported by Russian Foundation of Basic Research (# 08-04-00790).

Altered activation of AKT is required for the suppressive function of human CD4+CD25+ T regulatory cells

AbstractSuppression by T regulatory cells (Treg cells) is a major mechanism by which the immune system controls responses to self and nonharmful foreign proteins. Although there are many different types of Treg cells, the best characterized are those that constitutively express cell-surface IL-2Rα (CD25). We investigated whether altered T-cell–receptor (TCR)–mediated signaling in pure populations of ex vivo human CD4+CD25+ Treg cells might underlie their unique phenotype, including hyporesponsiveness to TCR–mediated activation and lack of cytokine production. CD4+CD25+ Treg cells displayed a consistent defect in phosphorylation of AKT at serine 473 and reduced phosphorylation of the AKT substrates FOXO and S6. Restoration of AKT activity via lentiviral-mediated expression of an inducibly active form of the kinase revealed that reduced activity of this pathway was necessary for the suppressive function of CD4+CD25+ Treg cells. These data represent the first demonstration of a causal association between altered signaling and the function of CD4+CD25+ Treg cells. Moreover, we have created the first system allowing inducible abrogation of suppression through manipulation of the suppressor cells. This system will be a powerful tool to further study the mechanism(s) of suppression by CD4+CD25+ Treg cells.

Operationally Tolerant and Minimally Immunosuppressed Kidney Recipients Display Strongly Altered Blood T-Cell Clonal Regulation

Most kidney transplant recipients who discontinue immunosuppression reject their graft. Nevertheless, a small number do not, suggesting that allogeneic tolerance state (referred to operational tolerance) is achievable in humans. So far, however, the rarity of such patients has limited their study. Because operational tolerance could be linked to anergy, ignorance or to an active regulatory mechanism, we analyzed the blood T-cell repertoire usage of these patients. We report on comparison of T-cell selection in drug-free operationally tolerant kidney recipients (or with minimal immunosuppression), recipients with stable graft function, chronic rejection and healthy individuals. The blood T cells of operationally tolerant patients display two major characteristics: an unexpected strongly altered T-cell receptor (TCR) Vbeta usage and high TCR transcript accumulation in selected T cells. The cytokine transcriptional patterns of sorted T cells with altered TCR usage show no accumulation of cytokine transcripts (IL10, IL2, IL13, IFN-gamma), suggesting a state of hyporesponsiveness in these patients. Identification of such a potential surrogate pattern of operational tolerance in transplant recipients under life-long immunosuppression may provide a new basis and rationale for exploration of tolerance state. However, these data obtained in a limited number of patients require further confirmation on larger series.