T-cell Pool Research Articles

Therapeutic Potential of Targeting Malt1-Dependent TCR Downstream Signaling to Promote the Survival of MHC-Mismatched Allografts.

Strategies targeting T cells are the cornerstone of immunosuppression after solid organ transplantation. The transcription factor NF-κB is a key regulator of downstream T-cell activation and induction of inflammatory mediators; its full activation via antigen receptor engagement requires both the scaffold and the protease activity of the paracaspase Malt1. Experimental studies have highlighted that Malt1-deficient mice were resistant to experimental autoimmune encephalomyelitis, although they lacked peripheral regulatory T cells (Treg). Here, we compared targeting Malt1 versus using calcineurin inhibitors as immunosuppression in a stringent experimental transplantation model. We found that Malt1-deficiency impaired Th1-mediated alloresponses in vitro and in vivo and significantly prolonged MHC-mismatched skin allograft survival, compared to cyclosporine. However, it paradoxically enhanced Th17 differentiation in the transplantation setting. Interestingly, more selective inhibition of Malt1 protease activity in wild-type mouse and human peripheral T cells in vitro led to attenuation of alloreactive Th1 cells, while preserving preexisting Treg in the peripheral T-cell pool, and without promoting Th17 differentiation. Thus, there is a place for further investigation of the role of Malt1 signaling in the setting of transplantation.

Recipient-specific T-cell repertoire reconstitution in the gut following murine hematopoietic cell transplant

AbstractGraft-versus-host disease (GVHD) is a complication of hematopoietic cell transplantation (HCT) caused by alloreactive T cells. Murine models of HCT are used to understand GVHD and T-cell reconstitution in GVHD target organs, most notably the gastrointestinal (GI) tract where the disease contributes most to patient mortality. T-cell receptor (TCR) repertoire sequencing was used to measure T-cell reconstitution from the same donor graft (C57BL/6 H-2b) in the GI tract of different recipients across a spectrum of matching, from syngeneic (C57BL/6), to minor histocompatibility (MHC) antigen mismatch BALB.B (H-2b), to major MHC mismatched B10.BR (H-2k) and BALB/c (H-2d). Although the donor T-cell pools had highly similar TCR, the TCR repertoire after HCT was very specific to recipients in each experiment independent of geography. A single invariant natural killer T clone was identifiable in every recipient group and was enriched in syngeneic recipients according to clonal count and confirmatory flow cytometry. Using a novel cluster analysis of the TCR repertoire, we could classify recipient groups based only on their CDR3 size distribution or TCR repertoire relatedness. Using a method for evaluating the contribution of common TCR motifs to relatedness, we found that reproducible sets of clones were associated with specific recipient groups within each experiment and that relatedness did not necessarily depend on the most common clones in allogeneic recipients. This finding suggests that TCR reconstitution is highly stochastic and likely does not depend on the evaluation of the most expanded TCR clones in any individual recipient but instead depends on a complex polyclonal architecture.

Cellular and molecular profiling of T-cell subsets at the onset of human acute GVHD

AbstractThe cellular and molecular processes involved in acute graft-versus-host disease (aGVHD) development early after allogeneic hematopoietic cell transplantation (HCT) in humans remain largely unknown. We have performed multiparameter immunophenotyping and molecular profiling of CD4+and CD8+T cells in 2 independent cohorts of patients undergoing HCT, as well as in their HLA-identical sibling donors. Cellular profiling using spectral flow cytometry showed an incomplete reconstitution of the T-cell compartment in recipients without aGVHD early after transplantation, as well as a shift toward an effector memory phenotype, paralleled by depletion of the naive T-cell pool. Molecular profiling of T-cell populations in donors vs recipients without aGVHD revealed increased pathway activity of >40 gene modules in recipients. These pathways were associated in particular with T-cell activation, adhesion, migration, and effector functions. Cellular profiles from recipients developing aGVHD displayed an enrichment of cells with a T memory stem cell–like phenotype compared with recipients without aGVHD. Comparison of gene profiles from these recipients revealed that transforming growth factor-β (TGF-β) signaling was most significantly downregulated, whereas the pathway activity of NF-κB–associated transcription factors and signaling pathways were increased, at aGVHD onset. This study suggests that the integration of cellular and molecular profiles provides new insights into the development of aGVHD in humans.

Revisiting CD8 T-cell 'Memory Inflation': New Insights with Implications for Cytomegaloviruses as Vaccine Vectors.

Murine models of cytomegalovirus (CMV) infection have revealed an exceptional kinetics of the immune response. After resolution of productive infection, transient contraction of the viral epitope-specific CD8 T-cell pool was found to be followed by a pool expansion specific for certain viral epitopes during non-productive ‘latent’ infection. This phenomenon, known as ‘memory inflation’ (MI), was found to be based on inflationary KLRG1+CD62L− effector-memory T cells (iTEM) that depend on repetitive restimulation. MI gained substantial interest for employing CMV as vaccine vector by replacing MI-driving CMV epitopes with foreign epitopes for generating high numbers of protective memory cells specific for unrelated pathogens. The concept of an MI-driving CMV vector is questioned by human studies disputing MI in humans. A bias towards MI in experimental models may have resulted from systemic infection. We have here studied local murine CMV infection as a route that is more closely matching routine human vaccine application. Notably, KLRG1−CD62L+ central memory T cells (TCM) and conventional KLRG1−CD62L− effector memory T cells (cTEM) were found to expand, associated with ‘avidity maturation’, whereas the pool size of iTEM steadily declined over time. The establishment of high avidity CD8 T-cell central memory encourages one to pursue the concept of CMV vector-based vaccines.

Moderate physical activity associated with a higher naïve/memory T-cell ratio in healthy old individuals: potential role of IL15.

ageing is accompanied by impairments in immune responses due to remodelling of the immune system (immunesenescence). Additionally, a decline in habitual physical activity has been reported in older adults. We have recently published that specific features of immunesenescence, such as thymic involution and naïve/memory T-cell ratio, are prevented by maintenance of a high level of physical activity. This study compares immune ageing between sedentary and physically active older adults. a cross-sectional study recruited 211 healthy older adults (60-79years) and assessed their physical activity levels using an actigraph. We compared T- and B-cell immune parameters between relatively sedentary (n = 25) taking 2,000-4,500 steps/day and more physically active older adults (n = 25) taking 10,500-15,000 steps/day. we found a higher frequency of naïve CD4 (P = 0.01) and CD8 (P = 0.02) and a lower frequency of memory CD4 cells (P = 0.01) and CD8 (P = 0.04) T cells in the physically active group compared with the sedentary group. Elevated serum IL7 (P = 0.03) and IL15 (P = 0.003), cytokines that play an essential role in T-cell survival, were seen in the physically active group. Interestingly, a positive association was observed between IL15 levels and peripheral CD4 naïve T-cell frequency (P = 0.023). we conclude that a moderate level of physical activity may be required to give a very broad suppression of immune ageing, though 10,500-15,000 steps/day has a beneficial effect on the naïve T-cell pool.

Eomes broadens the scope of CD8 T-cell memory by inhibiting apoptosis in cells of low affinity.

The memory CD8 T-cell pool must select for clones that bind immunodominant epitopes with high affinity to efficiently counter reinfection. At the same time, it must retain a level of clonal diversity to allow recognition of pathogens with mutated epitopes. How the level of diversity within the memory pool is controlled is unclear, especially in the context of a selective drive for antigen affinity. We find that preservation of clones that bind the activating antigen with low affinity depends on expression of the transcription factor Eomes in the first days after antigen encounter. Eomes is induced at low activating signal strength and directly drives transcription of the prosurvival protein Bcl-2. At higher signal intensity, T-bet is induced which suppresses Bcl-2 and causes a relative survival advantage for cells of low affinity. Clones activated with high-affinity antigen form memory largely independent of Eomes and have a proliferative advantage over clones that bind the same antigen with low affinity. This causes high-affinity clones to prevail in the memory pool, despite their relative survival deficit. Genetic or therapeutic targeting of the Eomes/Bcl-2 axis reduces the clonal diversity of the memory pool, which diminishes its ability to respond to pathogens carrying mutations in immunodominant epitopes. Thus, we demonstrate on a molecular level how sufficient diversity of the memory pool is established in an environment of affinity-based selection.

Reconstitution of T-cell-mediated immunity in patients after allogeneic stem cell transplantation

Background. The timely reconstitution of the donor-derived immune system is a key factor in the prevention of such post-transplant complications as graft versus host disease, relapse or secondary tumours and various infections. These complications affect the long-term survival of patients after allogeneic stem cell transplantation.Aim — to describe the main stages of T Cell–mediated immune recovery in patients after allogeneic stem cell transplantation.General findings. T-cell–mediated immunity is responsible for anti-infective and anti-tumour immune response. The early post-transplant period is characterized by the thymus-independent pathway of T-cell recovery largely involving proliferation of mature donor T cells, which were transplanted to the patient together with hematopoietic stem cells. To a lesser extent, this recovery pathway is realized through the expansion of host naïve and memory T cells, which survived after conditioning. Thymus-dependent reconstitution involves generation of de novo naïve T cells and subsequent formation of a pool of memory T-cells providing the main immunological effects — graft versus tumour and graft versus host reactions. A better understanding of the T-cell immune reconstitution process is important for selecting optimized pre-transplant conditioning regimens and patient-specific immunosuppressive therapy approaches, thus reducing the risks of post-transplant complications and improving the long-term survival of patients after allogeneic stem cell transplantation.

РОЛЬ ОТДЕЛЬНЫХ СУБПОПУЛЯЦИЙ CD4+ Т-ЛИМФОЦИТОВ В ПАТОГЕНЕЗЕ ВИЧ-ИНФЕКЦИИ

CD4+ T-cell pool is composed of cells residing in different maturation stages. Naive CD4+ T-lymphocytes, CD4+ stem memory T-cells, CD4+ central and effector memory T-lymphocytes perform var-ious functions in maintaining the immune system homeostasis. Despite phenotypic differences, each of those cells can be infected with HIV. Specific features of distinct CD4+ T-lymphocyte subsets determine their role in HIV-infection pathogenesis. By analyzing changes of CD4+ T-lymphocyte subset composi-tion, one can estimate the degree of the immune system damage and make predictions of immune recov-ery under highly active antiretroviral therapy. The article summarizes the main events occurring with CD4+ T-cell subsets during HIV-infection.

Limited effect of duration of CMV infection on adaptive immunity and frailty: insights from a 27-year-long longitudinal study.

ObjectivesCytomegalovirus infection is thought to affect the immune system and to impact general health during ageing. Higher CMV‐specific antibody levels in the elderly are generally assumed to reflect experienced viral reactivation during life. Furthermore, high levels of terminally differentiated and CMV‐specific T cells are hallmarks of CMV infection, which are thought to expand over time, a process also referred to as memory inflation.MethodsWe studied CMV‐specific antibody levels over ~ 27 years in 268 individuals (aged 60–89 years at study endpoint), and to link duration of CMV infection to T‐cell numbers, CMV‐specific T‐cell functions, frailty and cardiovascular disease at study endpoint.ResultsIn our study, 136/268 individuals were long‐term CMV seropositive and 19 seroconverted during follow‐up (seroconversion rate: 0.56%/year). CMV‐specific antibody levels increased slightly over time. However, we did not find an association between duration of CMV infection and CMV‐specific antibody levels at study endpoint. No clear association between duration of CMV infection and the size and function of the memory T‐cell pool was observed. Elevated CMV‐specific antibody levels were associated with the prevalence of cardiovascular disease but not with frailty. Age at CMV seroconversion was positively associated with CMV‐specific antibody levels, memory CD4+ T‐cell numbers and frailty.ConclusionCytomegalovirus‐specific memory T cells develop shortly after CMV seroconversion but do not seem to further increase over time. Age‐related effects other than duration of CMV infection seem to contribute to CMV‐induced changes in the immune system. Although CMV‐specific immunity is not evidently linked to frailty, it tends to associate with higher prevalence of cardiovascular disease.

Modified Vaccinia Ankara-Vectored Vaccine Expressing Nucleoprotein and Matrix Protein 1 (M1) Activates Mucosal M1-Specific T-Cell Immunity and Tissue-Resident Memory T Cells in Human Nasopharynx-Associated Lymphoid Tissue.

BackgroundIncreasing evidence supports a critical role of CD8+ T-cell immunity against influenza. Activation of mucosal CD8+ T cells, particularly tissue-resident memory T (TRM) cells recognizing conserved epitopes would mediate rapid and broad protection. Matrix protein 1 (M1) is a well-conserved internal protein. MethodsWe studied the capacity of modified vaccinia Ankara (MVA)–vectored vaccine expressing nucleoprotein (NP) and M1 (MVA-NP+M1) to activate M1-specific CD8+ T-cell response, including TRM cells, in nasopharynx-associated lymphoid tissue from children and adults. ResultsAfter MVA-NP+M1 stimulation, M1 was abundantly expressed in adenotonsillar epithelial cells and B cells. MVA-NP+M1 activated a marked interferon γ–secreting T-cell response to M1 peptides. Using tetramer staining, we showed the vaccine activated a marked increase in M158–66 peptide-specific CD8+ T cells in tonsillar mononuclear cells of HLA-matched individuals. We also demonstrated MVA-NP+M1 activated a substantial increase in TRM cells exhibiting effector memory T-cell phenotype. On recall antigen recognition, M1-specific T cells rapidly undergo cytotoxic degranulation, release granzyme B and proinflammatory cytokines, leading to target cell killing. Conclusions MVA-NP+M1 elicits a substantial M1-specific T-cell response, including TRM cells, in nasopharynx-associated lymphoid tissue, demonstrating its strong capacity to expand memory T-cell pool exhibiting effector memory T-cell phenotype, therefore offering great potential for rapid and broad protection against influenza reinfection.

Immune Profiling of Relapsed/Refractory Multiple Myeloma Patients Treated with Venetoclax in Combination with Dexamethasone (VenDex), Daratumumab and Dexamethasone (VenDd), and Daratumumab, Bortezomib and Dexamethasone (VenDVd)

Background: The BCL-2 family of anti-apoptotic proteins (e.g., BCL-2, BCL-XL, MCL-1) are important regulators of lymphocyte development and are therapeutic targets for hematologic malignancies, including multiple myeloma (MM). Venetoclax (Ven) is a highly selective, potent, oral BCL-2 inhibitor that induces apoptosis in MM cells and has shown synergistic activity with bortezomib (Velcade; V) and dexamethasone (Dex or d). Combination of the CD38 monoclonal antibody (mAb) daratumumab (D) with Ven is hypothesized to further increase anti-myeloma activity based upon dual mechanisms of pro-apoptotic effects on tumor cells as well as enhanced immune stimulation. Pre-clinically and in healthy human subjects, Ven treatment leads to enrichment of CD8+ T effector memory cells, while resulting in loss of CD4+ and CD8+ naïve T-cells, however the potential immunomodulatory effect of Ven in MM is unknown. Results presented herein describe the pharmacodynamic changes observed in immune cell subsets in relapsed/refractory (R/R) MM patients (pts) treated with VenDex, VenDd, and VenDVd. Methods: Peripheral blood samples were collected at day 1 of cycles 1-5 to characterize pharmacodynamic changes in B- and T-cell sub-populations by multicolor flow cytometry in Ven MM clinical trials M13-367 (NCT01794520) and M15-654 (NCT03314181). M13-367 is a phase 1/2 study of VenDex in t(11;14) R/R MM, and M15-654 is a phase 1/2 study of VenDd in t(11;14) R/R MM (Part 1) and VenDVd in R/R MM (Part 2). As of 12 June 2019, 15 out of 31 pts treated with VenDex in phase 2 of M13-367, 19 out of 24 pts treated in Part 1 (VenDd), and 19 out of 24 pts treated in Part 2 (VenDVd) of M15-654 had baseline and post-treatment specimens available for analysis. Results: Consistent with previous findings that B-cells are highly dependent upon BCL-2 for cell survival, each Ven-containing regimen (VenDex, VenDd, and VenDVd) resulted in rapid and sustained reduction (~90% decrease from baseline by end of cycle 1) in peripheral B-cell (CD19+/CD5-) counts (Figure). In subgroup analyses, naïve B-cells (CD27-/IgM+) were significantly reduced in pts treated with each regimen, however regulatory B-cells (CD27+/CD24+) remained largely unaffected. In addition, a decrease in plasmablasts (CD27+CD38+CD20-) were only observed in pts treated with D-containing regimens (VenDd and VenDVd), which is consistent with expression of CD38 in this subgroup. In contrast to B-cells, CD3+ T-cells were minimally reduced (~20-30% reduction from baseline through end of cycle 4) with VenDex and VenDd treatment. A more prominent reduction was observed in pts treated with VenDVd (~50-60% reduction from baseline through end of cycle 4). CD4+ T-cells were more sensitive than CD8+ T-cells to VenDex and VenDd, while both CD4+ and CD8+ T-cells were reduced in VenDVd treated pts (Figure). T-cell subgroup analyses were also performed, including naïve T-cells (CD45RA+/CD197+), effector (CD45RA+/CD197-), effector memory (CD45RA-/CD197-), and central memory (CD45RA-/CD197+). Overall, there were no significant changes in the composition of the T-cell pool (Tnaive, TCM, TEM, TEMRA) or in Th1 (CD4+/CD183+/CD196-), Th2 (CD4+/CD183-/CD196-), and Th17 (CD4+/CD183-/CD196+) cells in pts treated with VenDex, VenDd, or VenDVd. Finally, a decrease in Tregs (CD4+/CD25+/CD127low/CD194+) was observed in VenDd and VenDVd treated pts, but not in VenDex treated pts (Figure). While no reduction in overall Tregs was observed with VenDex, a decrease in the relative proportion of activated Tregs (HLA-DR+/CD45RO+) to naïve (HLA-DR-/CD45RO-) and memory (HLA-DR-/CD45RO+) Tregs was observed. Conclusions: Comprehensive immunophenotyping studies were conducted to characterize the potential effects of Ven in B- and T-cell subsets when used in combination with standard of care anti-myeloma agents of various mechanisms of action (i.e. glucocorticoid, CD38 mAb and/or proteasome inhibitor). While each Ven combination regimen resulted in significant reductions in circulating B-cells, T-cell effects were largely dependent upon the combination regimen. Minimal reduction in total T-cell counts were observed with VenDex and VenDd, which were primarily due to reduction in CD4+ T-cells. However, the extent of T-cell depletion (CD4+ and CD8+ T-cells) was greatest in pts treated with the bortezomib-containing regimen VenDVd. Correlative studies between immune profiles and pt outcomes are ongoing. Disclosures Vishwamitra: AbbVie: Employment, Other: stock or other options. Mantis:AbbVie Inc: Employment, Other: Stock/stock options. Haribhai:AbbVie: Employment, Other: stock or other options. Uziel:AbbVie: Employment, Other: stock or other options. Leverson:AbbVie Inc: Employment, Other: Stock or options. Pauff:AbbVie Inc: Employment, Other: may own stock or stock options. Bueno:AbbVie: Employment, Other: Stock/stock options. Maciag:AbbVie: Employment, Other: Stock/stock options. Ross:AbbVie: Employment, Other: Stock/stock options.

Influence of congenital heart disease-caused hypoxia on intrathymic development of t-lymphocytes in children of first year of life

Aim. To study the influence of hypoxia, caused by congenital heart disease, on the intrathymic development of T-lymphocytes and provision of the organism with T-cellular resource in children with cardiac pathology of different degree of severity.
 Materials and methods. The paper presents the results of complex immunomorphological study of the thymus in children of the first year of life (n = 129) with congenital heart diseases. Hystochemical and immunological methods were used to assess the influence of congenital heart disease-caused hypoxia on the functional status of thymus regarding provision of a child with T-lymphocytes.
 Results. It was established that the degree of severity of congenital heart disease correlated with the degree of suppression of T-lymphocyte pool formation. During the first year of life, proliferative activity of thymocytes (assessed by Ki-67 expression) in the thymus falls, being the reason of decrease in the number of CD3+ thymocytes. In conditions of marked hypoxia (blue type of defect) the process of T-lymphocyte differentiation is inhibited that causes preservation of less mature forms of thymocytes. As a result, hypoxia is the reason of proliferation suppression and thymocyte differentiation, influencing subpopulation composition of the cells. Thus, insufficient quantity of thymic migrants enters the peripheral blood that confirms low functional activity of thymus regarding provision of the organism with T-cellular resource.
 Conclusions. No doubt, it can be the cause of immunodeficient state and reduced formation of adaptive immunity in this category of children.

Influence of violations of non-specific and systemic cell response to the efficiency of the chemotherapy of pulmonary multidrug-resistant tuberculosis

Objective — is to establish violations in the immune system that aggravate the course and reduce the effectiveness of the treatment of patients with multidrug­resistant pulmonary tuberculosis.Materials and methods. A comparative analysis of violations of the non­specific and systemic cellular immune response at the link was performed in 44 patients with a newly diagnosed destructive multidrug­resistant pulmonary tuberculosis (NDD MDR-TB) with effective, not very effective and ineffective antimycobacterial therapy (AMBT).Results and discussion. In patients with NDD MDR-TB inefficient and not very effective therapy, compared to patients treated efficiently, available pronounced humoral type immune response: increased by an average of 20—25 % content of ІgА (р < 0.05), ІgМ (р < 0.05), ІgЕ (р < 0.05) and the level of circulating immune complexes (p < 0.05); reduced content of cationic lysosomal proteins (CLP) of granulocytic leukocytes (р < 0.001), suppressed proliferative activity of T-lymphocytes on nonspecific (FSH, p < 0.05) and specific (PPD-L, p < 0.05) mytogens. In patients with treatment failure 2.0 times more frequently observed inhibition of 30 — 50.0 % or more proliferative activity of T-lymphocytes, the proportion of individuals with signs of tuberculin anergy of specific T-lymphocytes increased in 1.7 times and the proportion of patients with a decreased content of CLP granulocytes increased in 1.5 times. Significant disorders in the immune system were detected in 70 % of patients with ineffective and 29.4 % of patients with effective treatment.Conclusions. Progression specific process and reduce of the efficiency AMBT MDR-TB contribute: the presence of T-cell immunosuppression expressed by a decrease of more than 30.0 % of the T-lymphocyte pool and inhibition of their proliferative activity; tuberculin tolerance of specific T-lymphocytes, phago­cytic insufficiency is caused by a decrease of 30.0—50.0 % of the CLP content of granulocytic leukocytes.

Natural Tr1-like cells do not confer long-term tolerogenic memory.

IL-10-producing Tr1 cells promote tolerance but their contributions to tolerogenic memory are unclear. Using 10BiT mice that carry a Foxp3-eGFP reporter and stably express CD90.1 following IL-10 production, we characterized the spatiotemporal dynamics of Tr1 cells in a house dust mite model of allergic airway inflammation. CD90.1+Foxp3-IL-10+ Tr1 cells arise from memory cells and rejoin the tissue-resident memory T-cell pool after cessation of IL-10 production. Persistent antigenic stimulation is necessary to sustain IL-10 production and Irf1 and Batf expression distinguishes CD90.1+Foxp3-IL-10+ Tr1 cells from CD90.1+Foxp3-IL-10- 'former' Tr1. Depletion of Tr1-like cells after primary sensitization exacerbates allergic airway inflammation. However, neither transfer nor depletion of former Tr1 cells influences either Tr1 numbers or the inflammatory response during subsequent allergen memory re-challenge weeks later. Together these data suggest that naturally-arising Tr1 cells do not necessarily give rise to more Tr1 upon allergen re-challenge or contribute to tolerogenic memory. This phenotypic instability may limit efforts to re-establish tolerance by expanding Tr1 in vivo.

Characterization of memory T cells in individuals resistant to Schistosoma mansoni infection

To evaluate the frequency of memory CD4+ and CD8+ T cells from individuals resistant and susceptible to Schistosoma mansoni infection. We selected individuals with low (resistant) and high (susceptible) parasite burden using databases generated during previous studies carried out in the same endemic area. The cell surface markers were performed using flow cytometry. In this study, the resistant individuals showed an increase in the CD4+ memory T-cell pool associated with an increase in the central memory cell (TCM) and a decrease in the effector memory cell (TEM ). Individuals susceptible to infection had higher frequencies of effector memory cells compared to resistant individuals. These data suggest that resistance to Smansoni infection may be associated with an increase in the number of CD4+ memory T cells and susceptibility to infection is associated with a decrease in the central memory cell as well as high proportions of effector memory cells.

Reduced positive selection of a human TCR in a swine thymus using a humanized mouse model for xenotolerance induction.

Tolerance-inducing approaches to xenotransplantation would be optimal and may be necessary for long-term survival of transplanted pig organs in human patients. The ideal approach would generate donor-specific unresponsiveness to the pig organ without suppressing the patient's normal immune function. Porcine thymus transplantation has shown efficacy in promoting xenotolerance in humanized mice and large animal models. However, murine studies demonstrate that T cells selected in a swine thymus are positively selected only by swine thymic epithelial cells, and therefore, cells expressing human HLA-restricted TCRs may not be selected efficiently in a transplanted pig thymus. This may lead to suboptimal patient immune function. To assess human thymocyte selection in a pig thymus, we used a TCR transgenic humanized mouse model to study positive selection of cells expressing the MART1 TCR, a well-characterized human HLA-A2-restricted TCR, in a grafted pig thymus. Positive selection of T cells expressing the MART1 TCR was inefficient in both a non-selecting human HLA-A2- or swine thymus compared with an HLA-A2+ thymus. Additionally, CD8 MART1 TCRbright T cells were detected in the spleens of mice transplanted with HLA-A2+ thymi but were significantly reduced in the spleens of mice transplanted with swine or HLA-A2- thymi. [Correction added on October 15, 2019, after first online publication: The missing superscript values +, -, and bright have been included in the Results section.] CONCLUSIONS: Positive selection of cells expressing a human-restricted TCR in a transplanted pig thymus is inefficient, suggesting that modifications to improve positive selection of cells expressing human-restricted TCRs in a pig thymus may be necessary to support development of a protective human T-cell pool in future patients.

Quantitative characterization of T-cell repertoire alteration in Chinese patients with B-cell acute lymphocyte leukemia after CAR-T therapy.

Chimeric antigen receptor (CAR) T-cell therapy has displayed potent anti-leukemia activity in acute lymphocytic leukemia (ALL), acting as a new ray of hope to refractory/relapsed patients. However, the influence of CAR-T therapy on host immune system has not been well elucidated. Thus, We applied high-throughput T cell receptor β chain sequencing to track the dynamic change of T-cell repertoire induced by CAR-T therapy in B-cell ALL patients. Six Chinese patients achieving complete remission were under observation, whose blood samples, bone marrow samples and infused CAR-T samples were collected at serial time points before and after CAR-T therapy. We observed decreased TCR diversity and increased clonality of T-cell repertoire in both peripheral blood and bone marrow after CAR-T administration. The persistent T cell clones in blood and bone marrow expanded following leukemic cell destruction and were barely detected in CAR T-cell pool. For the first time, our results demonstrated CAR-T therapy could stimulate the clonal proliferation of CAR-negative T cells in patients. Considering other groups' animal results indicating that CAR-T therapy could facilitate the proliferation of tumor antigen-specific T cells and that the emergence of these T cell clones followed the destruction of leukemic cells, they are most likely tumor antigen-specific.

Six weeks of strength endurance training decreases circulating senescence-prone T-lymphocytes in cytomegalovirus seropositive but not seronegative older women

BackgroundAgeing is associated with a decline in immune function termed immunosenescence. This process is characterized amongst others by less naive T-cells and more senescent phenotypes, which have been implicated in the pathogenesis of many age-related diseases. Thus far, reports regarding the long-term adaptation effects of exercise on T-cell phenotypes are scant and largely equivocal. These inconsistencies may be due to potential contributors to immunosenescence, particularly cytomegalovirus infection, which is considered a hallmark of T-cell senescence. Therefore, we sought to investigate the impact of cytomegalovirus serostatus on the distribution of peripheral T-cell subsets following long-term exercise in older women.MethodsOne hundred women (aged 65 years and above) were randomized to 3 times/weekly training at either intensive strength training (3 × 10 repetitions at 80% of one-repetition maximum, n = 31), strength endurance training (2 × 30 repetitions at 40% of one-repetition maximum, n = 33), or control (passive stretching exercise, n = 36) for 6 weeks. All training sessions were supervised by trained instructors to minimize the risk of injury and to ensure that the participants adhered to the training protocol throughout the entire range of motion. The T-cell percentages and absolute blood counts were determined before and after 6 weeks (24 h–48 h after the last training session) using flow cytometry and a haematology analyser. Cytomegalovirus antibodies were measured in serum using Architect iSystem and cytomegalovirus serostatus was balanced in the three intervention groups. C-reactive protein was measured using immunonephelometry.ResultsWe report for the first time that 6 weeks of strength endurance training significantly decreased senescence-prone T-cells along with a small increase in the number of CD8– naive T-cells in blood. The absolute counts of senescent-like T-cells decreased by 44% (from 26.03 ± 35.27 to 14.66 ± 21.36 cells/μL, p < 0.01) and by 51% (from 6.55 ± 12.37 to 3.18 ± 6.83 cells/μL, p < 0.05) for the CD8+ and CD8– T-cell pools, respectively. Intriguingly, these changes were observed in cytomegalovirus seropositive, but not cytomegalovirus seronegative individuals.ConclusionsIn conclusion, the present study shows that strength endurance training leads to a reduction in circulating senescence-prone T-cells in cytomegalovirus seropositive older women. It remains to be established if monitoring of peripheral senescence-prone T-cells may have utility as cellular biomarkers of immunosenescence.

Adaptive immune response in residents of the Russian Arctic zone and South Ossetia

The human body in adverse living conditions, such as in the Arctic, goes through the risk of impairing functional systems including the immune system. These disturbances lead to appear states of weakness or hyperactivity of the organism protective function. This study investigates the state of the adaptive immune response of 40-60-year-old women living in the Russian Arctic and South Ossetia. The indirect immunoperoxidase assay with monoclonal antibodies was used to analyze the immune parameters of lymphoid subpopulations in 40-60-year-old women living in Nadym city in the Yamalo-Nenets Autonomous Okrug and in Tskhinval city in South Ossetia. After analyzing the received data, the deficiency of mature T-lymphocytes (CD3+) was found in 96-100% of the examined individuals. We also revealed a decrease in the concentration of T-helper (CD4+) and B-activated (HLA-DR+) cells in 30% of Arctic zone cases and in 50% of the southern zone cases on the background of increasing concentrations of cytotoxic T-lymphocytes. A deficiency of cells with apoptosis receptors (CD95+) was registered mainly in Tskhinval women (80%). Thus, it can be assumed that the deficiency of mature lymphoid cells with a receptor (CD3+) leads to disruption of the T-cell pool of the immune response and delay of the adaptive immune response overall. The increase in the cytotoxic T-lymphocyte count indicates the stress state of the adaptive immune component to compensate for the lack of T-helper and B-activated cells concentration. Additional comprehensive studies are needed to identify environmental factors having a significant impact on the mechanism of the adaptive immune response development.

Keratinocyte growth factor impairs human thymic recovery from lymphopenia.

BACKGROUNDThe lymphocyte-depleting antibody alemtuzumab is a highly effective treatment for relapsing-remitting multiple sclerosis (RRMS); however, 50% of patients develop novel autoimmunity after treatment. Most at risk are individuals who reconstitute their T cell pool by proliferating residual cells, rather than producing new T cells in the thymus, raising the possibility that autoimmunity might be prevented by increasing thymopoiesis. Keratinocyte growth factor (palifermin) promotes thymopoiesis in nonhuman primates.METHODSFollowing a dose tolerability substudy, individuals with RRMS (duration ≤10 years; expanded disability status scale ≤5.0, with ≥2 relapses in the previous 2 years) were randomized to placebo or 180 μg/kg/d palifermin, given for 3 days immediately before and after each cycle of alemtuzumab, with repeat doses at month 1 (M1) and M3. The interim primary endpoint was naive CD4+ T cell count at M6. Exploratory endpoints included number of recent thymic emigrants (RTEs) and signal joint T cell receptor excision circles/ml (sjTRECs/ml) of blood. The trial’s primary endpoint was incidence of autoimmunity at M30.RESULTSAt M6, individuals receiving palifermin had fewer naive CD4+ T cells (2.229 × 107/l vs. 7.733 × 107/l; P = 0.007), RTEs (16% vs. 34%), and sjTRECs/ml (1100 vs. 3396), leading to protocol-defined termination of recruitment. No difference was observed in the rate of autoimmunity between the 2 groups.CONCLUSIONIn contrast with animal studies, palifermin reduced thymopoiesis in our patients. These results offer a note of caution to those using palifermin to promote thymopoiesis in other settings, particularly in the oncology/hematology setting, where alemtuzumab is often used as part of the conditioning regime.TRIAL REGISTRATIONClinicalTrials.gov NCT01712945.FUNDINGMRC and Moulton Charitable Trust.