KLRG1+ Effector CD8+ T Cells Lose KLRG1, Differentiate into All Memory T Cell Lineages, and Convey Enhanced Protective Immunity.
ABSTRACT: Protective immunity against pathogens depends on the efficient generation of functionally diverse effector and memory T lymphocytes. However, whether plasticity during effector-to-memory CD8+ T cell differentiation affects memory lineage specification and functional versatility remains unclear. Using genetic fate mapping analysis of highly cytotoxic KLRG1+ effector CD8+ T cells, we demonstrated that KLRG1+ cells receiving intermediate amounts of activating and inflammatory signals downregulated KLRG1 during the contraction phase in a Bach2-dependent manner and differentiated into all memory T cell linages, including CX3CR1int peripheral memory cells and tissue-resident memory cells. "ExKLRG1" memory cells retained high cytotoxic and proliferative capacity distinct from other populations, which contributed to effective anti-influenza and anti-tumor immunity. Our work demonstrates that developmental plasticity of KLRG1+ effector CD8+ T cells is important in promoting functionally versatile memory cells and long-term protective immunity.
Project description:Killer cell lectin-like receptor subfamily G member 1 (KLRG1) has been found on human memory T lymphocytes. However, the roles of KLRG1 on human T cells especially in tumor microenvironment have not been fully understood. Our results showed KLRG1 expression on T cells significantly increased in tumor microenvironment. KLRG1+ T cells exhibited poor proliferative capacity with decreased effector cytokine production. Meanwhile, KLRG1+ T cells expressed abundant pro-inflammatory cytokines and demonstrated high level of Foxp3 expression. KLRG1+ T cells showed decreased expression of miRNA-101 and higher expression of CtBP2. Our results indicated KLRG1 might contribute to the impaired antitumor immunity of memory T cells in tumor microenvironment. Thus, repressing KLRG1 on human memory T cells might be a novel therapeutics against cancer.
Project description:CMV remains an important opportunistic pathogen in high-risk lung transplant recipients. We characterized the phenotype and function of CD8+ T cells from acute/primary into chronic CMV infection in 23 (donor+/recipient-; D+R-) lung transplant recipients and found rapid induction of both KLRG1+ and/or CD57+ CMV-specific CD8+ T cells with unexpected coexpression of CD27. These cells demonstrated maturation from an acute effector T cell (TAEFF) to an effector memory T cell (TEM) phenotype with progressive enrichment of KLRG1+CD57+CD27- cells into memory. CMV-specific KLRG1+ TAEFF were capable of in vitro proliferation that diminished upon acquisition of CD57, whereas only KLRG1+ expression correlated with T-bet expression and effector function. In contrast to blood TAEFF, lung mucosal TAEFF demonstrated reduced KLRG1/T-bet expression but similar CD57 levels. Additionally, increased KLRG1+TAEFF were associated with early immune viral control following primary infection. To our knowledge, our findings provide new insights into the roles of KLRG1 and CD57 expression in human T cells, forming the basis for a refined model of CD8+ T cell differentiation during CMV infection.
Project description:Intestinal tissue-resident memory CD8 T cells (Trm) are non-recirculating effector cells ideally positioned to detect and react to microbial infections in the gut mucosa. There is an emerging understanding of Trm cell differentiation and functions, but their implication in inflammatory bowel diseases, such as Crohn's disease (CD), is still unknown. Here, we describe CD8 cells in the human intestine expressing KLRG1 or CD103, two receptors of E-cadherin. While CD103 CD8 T cells are present in high numbers in the mucosa of CD patients and controls, KLRG1 CD8 T cells are increased in inflammatory conditions. Mucosal CD103 CD8 T cells are more responsive to TCR restimulation, but KLRG1 CD8 T cells show increased cytotoxic and proliferative potential. CD103 CD8 T cells originate mostly from KLRG1 negative cells after TCR triggering and TGF? stimulation. Interestingly, mucosal CD103 CD8 T cells from CD patients display major changes in their transcriptomic landscape compared to controls. They express Th17 related genes including CCL20, IL22, and IL26, which could contribute to the pathogenesis of CD. Overall, these findings suggest that CD103 CD8 T cells in CD induce a tissue-wide alert increasing innate immune responses and recruitment of effector cells such as KLRG1 CD8 T cells.
Project description:The graft-versus-leukemia effect reminds us to observe the allogeneic cell elicited anti-tumor immune responses. Here we immunized recipient B6 mice with different types of allogenic leukocytes and found that vaccination with allogenic dendritic cells (alloDC) elicited the most efficient protection against broad-spectrum tumors. The recipient lymphocytes were analyzed and the data showed that CD8 T cells increased significantly after immunization and expressed effector memory T cell marker KLRG1. Functional evaluation demonstrated that these KLRG1+CD8 T cells could kill tumor cells in vitro and in vivo in Granzyme B- and Fas/FasL-dependent manners with no tumor antigen specificity, and tend to migrate into tumor sites by high expression of heparanase. Adoptive transfer of these cells could provide antitumor protection against tumors. AlloDC could also treat mice with residual tumors and combination of anti-PD1 antibody could enhance this effects. Together, our study showed that alloDC-immunization could induce potent antitumor effect through the expansion of KLRG1+CD8 T cells, which can work as both preventive and therapeutic tumor vaccines.
Project description:Microsporidia, a latent opportunistic infection associated with mild inflammation, is characterized by a strong CD8 T cell response, which has been shown to be CD4 T cell dependent. In this manuscript, we demonstrate that CD4 help is provided via IL-21 production, a common ?-chain cytokine closely related to IL-2. The peak of IL-21 expression, observed during the acute infection, is associated with an elevated IL-21(+) CD4 T subset, and these cells bear a phenotypic resemblance to T follicular helper cells. We observed that, during per-oral microsporidial infection, IL-21 was critical for the generation of an optimal effector CD8 T cell immunity. Sharply decreased effector KLRG1(+) CD8 response was observed in IL-21R knockout mice, and although these cells exhibited reduced functional properties, they retained the ability to proliferate. The role of IL-21 in the generation of CD8 effectors was cell intrinsic, as stronger defects were observed in the IL-21-deficient compartment from the bone marrow chimeric mice (IL-21R knockout/wild-type). These findings are different from those reported for viral infections in which IL-21 has been primarily associated with the generation and maintenance of CD8 memory response. To the best of our knowledge, this report demonstrates a critical role for IL-21 in the generation of a primary effector CD8 T cell response to an infectious disease model.
Project description:During acute viral infections in mice, IL-7R? and KLRG1 together are used to distinguish the short-lived effector cells (SLEC; IL-7R?lo KLRGhi ) from the precursors of persisting memory cells (MPEC; IL-7R?hi KLRG1lo ). We here show that these markers can be used to define distinct subsets in the circulation and lymph nodes during the acute phase and in "steady state" in humans. In contrast to the T cells in the circulation, T cells derived from lymph nodes hardly contain any KLRG1-expressing cells. The four populations defined by IL-7R? and KLRG1 differ markedly in transcription factor, granzyme and chemokine receptor expression. When studying renal transplant recipients experiencing a primary hCMV and EBV infection, we also found that after viral control, during latency, Ki-67-negative SLEC can be found in the peripheral blood in considerable numbers. Thus, combined analyses of IL-7R? and KLRG1 expression on human herpes virus-specific CD8+ T cells can be used to separate functionally distinct subsets in humans. As a noncycling IL-7R?lo KLRG1hi population is abundant in healthy humans, we conclude that this combination of markers not only defines short-lived effector cells during the acute response but also stable effector cells that are formed and remain present during latent herpes infections.
Project description:<h4>Background</h4>KLRG1 is a lymphocyte co-inhibitory, or immune checkpoint, receptor expressed predominantly on late-differentiated effector and effector memory CD8+ T and NK cells. Targeting of KLRG1 neutralization in murine cancer models has not previously been reported.<h4>Methods</h4>We studied KLRG1 expression in human blood and tumor samples from available genomic datasets. Anti-KLRG1 neutralizing antibody was studied in the murine 4T1 breast cancer as monotherapy, and in the MC38 colon cancer and B16F10 melanoma models as combination therapy with anti-PD-1 antibody.<h4>Results</h4>In human blood and tumor samples, KLRG1 expression is aligned with cytotoxic T and NK cell differentiation, and upregulated in human tumor samples after a variety of therapies, potentially contributing to adaptive resistance. In <i>in vivo</i> murine models, anti-KLRG1 antibody monotherapy in the 4T1 breast cancer model reduced lung metastases (decreased lung weights p=0.04; decreased nodule count p=0.002), while anti-KLRG1 + anti-PD-1 combination therapy in the MC38 colon cancer and B16F10 melanoma models produced synergistic benefit greater than anti-PD-1 alone for tumor volume (MC38 p=0.01; B16F10 p=0.007) and survival (MC38 p=0.02; B16F10 p=0.002).<h4>Conclusions</h4>These studies provide the first evidence that inhibition of the KLRG1 pathway enhances immune control of cancer in murine models, and provide target validation for KLRG1 targeting of human cancer. The mechanism of efficacy of KLRG1 blockade in murine models remains to be determined.
Project description:Memory T cell inflation is a process in which a subset of cytomegalovirus (CMV) specific CD8 T cells continuously expands mainly during latent infection and establishes a large and stable population of effector memory cells in peripheral tissues. Here we set out to identify in vivo parameters that promote and limit CD8 T cell inflation in the context of MCMV infection. We found that the inflationary T cell pool comprised mainly high avidity CD8 T cells, outcompeting lower avidity CD8 T cells. Furthermore, the size of the inflationary T cell pool was not restricted by the availability of specific tissue niches, but it was directly related to the number of virus-specific CD8 T cells that were activated during priming. In particular, the amount of early-primed KLRG1- cells and the number of inflationary cells with a central memory phenotype were a critical determinant for the overall magnitude of the inflationary T cell pool. Inflationary memory CD8 T cells provided protection from a Vaccinia virus challenge and this protection directly correlated with the size of the inflationary memory T cell pool in peripheral tissues. These results highlight the remarkable protective potential of inflationary CD8 T cells that can be harnessed for CMV-based T cell vaccine approaches.
Project description:As acute infections resolve, most effector CD8(+) T cells die, whereas some persist and become memory T cells. Recent work showed that subsets of effector CD8(+) T cells, identified by reciprocal expression of killer cell lectin-like receptor G1 (KLRG1) and CD127, have different lifespans. Similar to previous reports, we found that effector CD8(+) T cells reported to have a longer lifespan (i.e., KLRG1(low)CD127(high)) have increased levels of Bcl-2 compared with their shorter-lived KLRG1(high)CD127(low) counterparts. Surprisingly, we found that these effector KLRG1(low)CD127(high) CD8(+) T cells also had increased levels of Bim compared with KLRG1(high)CD127(low) cells. Similar effects were observed in memory cells, in which CD8(+) central memory T cells expressed higher levels of Bim and Bcl-2 than did CD8(+) effector memory T cells. Using both pharmacologic and genetic approaches, we found that survival of both subsets of effector and memory CD8(+) T cells required Bcl-2 to combat the proapoptotic activity of Bim. Interestingly, inhibition or absence of Bcl-2 led to significantly decreased expression of Bim in surviving effector and memory T cells. In addition, manipulation of Bcl-2 levels by IL-7 or IL-15 also affected expression of Bim in effector CD8(+) T cells. Finally, we found that Bim levels were significantly increased in effector CD8(+) T cells lacking Bax and Bak. Together, these data indicate that cells having the highest levels of Bim are selected against during contraction of the response and that Bcl-2 determines the level of Bim that effector and memory T cells can tolerate.