Project description:We profiled the heterogeneity of virtual memory T cells and observed changes in virtual memory T cell subsets under conditions of IL-4 deficiency in mouse spleens using single-cell RNA sequencing.
Project description:The development of virtual memory CD8 T cells is dependent on IL-4, type I interferon, and IL-15. However, it remains unclear whether these cytokines individually contribute to the generation of specific subsets of virtual memory CD8 T cells. In this study, virtual memory CD8 T cells were categorized into four subsets based on Ly6C and Sca-1 expression, and their development was examined using knock-out mice lacking IFNAR1, IL-4, or IL-15Rα. Notably, both Ly6C+ Sca-1+ and Ly6C- Sca-1+ subsets were significantly reduced in the spleen of IFNAR1 knock-out mice, while the proportion of Ly6C+ Sca-1- VM CD8 T cells was reduced in IL-4-deficient mice. In IL-15Rα knock-out mice, both the Ly6C+ Sca-1- and Ly6C- Sca-1- subsets were significantly reduced. Bulk RNA sequencing analysis revealed distinct gene expression patterns in naïve cells, true memory cells, and four virtual memory cells subsets. Specifically, Ly6C+ subsets were enriched with IL-15 signal-related genes, whereas Ly6C- subsets and true memory cells were enriched for cell cycle-related genes. Functionally, the Ly6C+ subsets exhibited higher production of IFN-γ, TNF-α, and perforin compared to the Ly6C- subsets. Overall, this study demonstrates the heterogeneity of virtual memory CD8 T cells and highlights the cytokine-dependent nature for their development.
Project description:Virtual memory (VM) CD8+ T cells are cytokine-driven, memory-phenotype lymphocytes maintained independently of antigen exposure. However, their role in chronic hepatic inflammation remains poorly defined. Here, we examined whether signaling through the IL-15/Rα complex (IL-15C) modulates VM CD8+ T cell responses during chronic liver injury. Mice were pretreated with IL-15C prior to induction of chronic liver injury using thioacetamide (TAA). VM CD8+ phenotypes, transcriptional profiles, and hepatic accumulation were analyzed by flow cytometry and mRNA sequencing. Type I interferon-deficient and CD8-depleted mouse model were used to assess the contribution of cytokine signaling and CD8+ T cells to the observed responses. IL-15C induced robust expansion of VM CD8+ T cells in both the spleen and liver, with preferential enrichment of a Ly6C+Sca-1+ subsets. IL-15C reprogrammed VM CD8+ T cells toward an effector and migratory phenotype, characterized by increased expression of EOMES, T-bet, NKG2D, and inflammatory chemokine receptors, along with reduced tissue-residency signatures. During chronic TAA-induced liver inflammation, VM CD8+ T cells, particularly the Ly6C+Sca-1+ subsets, accumulated in the liver, and IL-15C pretreatment further enhanced hepatic immune cell infiltration and was associated with sustained liver injury and fibrotic responses. Notably, IL-15-induced VM T cells exhibited reduced PD-1 expression and sustained NKG2D expression, especially within CD62L+ and CD69+ VM T cell populations. These findings demonstrate that IL-15C drives the expansion and phenotypic reprogramming of VM CD8+ T cells toward an effector-like, migratory state and is associated with enhanced hepatic immune cell infiltration during chronic liver injury.
Project description:Parasitic helminths induce the production of interleukin (IL)-4 which causes the expansion of virtual memory CD8+ T cells (TVM), a cell subset contributing to the control of viral coinfection. However, the mechanisms regulating IL-4-dependent TVM activation and expansion during worm infection remain ill defined. We used single-cell RNA sequencing of CD8+ T cells to investigate IL-4-dependent TVM responses upon helminth infection in mice. Gene signature analysis of CD8+ T cells identified a cell cluster marked by CD22, a canonical regulator of B cell activation, as a specific and selective surface marker of IL-4-induced TVM cells. CD22+ TVM were enriched for IFN-γ and granzyme A and retained a diverse TCR repertoire, while enriched in CDR3 sequences with features of self-reactivity. Deletion of CD22 expression in CD8+ T cells enhanced TVM responses to helminth infection, indicating that this inhibitory receptor modulates TVM responses. Thus, helminth-induced IL-4 drives the expansion and activation of self-reactive TVM in the periphery that is counter-inhibited by CD22
Project description:Effects of IL-4 on CD8 T cells functions are largely unknown. IL-4 induces survival and proliferation of CD8 T cells, but several studies suggest that IL-4 could also affect several functions of CD8 T cells such as cytotoxicity. Our team has shown that IL-4 repress the expression of Ccl5 in vitro. To define more precisely the impact of IL-4 on CD8 T cells, we performed a whole genome expression microarray analysis of naive and memory CD8 T cells cultured in presence or absence of IL-4. This approach allowed us to define the IL4-gene-expression signature on CD8 T cells. 18 samples were processed. Two populations of F5 naive CD8 T cells were FACS-sorted: samples from each population were incubated 20 hours with IL-7 in presence or absence of IL-4. Thus, a total of 6 “Naive” samples were processed. In addition, 4 populations of F5 TIM memory CD8 T cells were FACS-sorted: samples from 2 of these populations were incubated 20 hours in presence of IL-7 and/or IL-4, or in medium alone. Thus, 12 “Memory” samples were processed.
Project description:Virtual memory T (TVM) cells are a T-cell subtype that exhibit a memory phenotype without prior exposure to a foreign antigen. Although several recent studies suggest that TVM cells exert anti-viral and anti-bacterial function, pathological roles of TVM cells causing inflammatory diseases have not been studied. Here, we identified a novel CD8+ T-cell subset (CD44s-hiCD49dlo CD8+ T cells), which is originated from TVM cells and can cause a chronic inflammatory disease, alopecia areata (AA). In the skin of alopecic mice, we detected a distinct TVM-cell subpopulation characterized by superior expression of CD44 and features of tissue residency, which was transcriptionally, phenotypically, and functionally distinct from conventional CD8+ TVM cells. Mechanistically, this cell population could be induced from conventional TVM cells by IL-12, IL-15, and IL-18 stimulation. Moreover, the pathological activity of CD44s-hiCD49dlo CD8+ T cells was mediated by NKG2D-depedent innate-like cytotoxicity against target cells, which was further augmented by IL-15 stimulation and triggered the onset of disease. Collectively, our results suggest a new immunological mechanism through which TVM cells can cause chronic inflammatory disease by innate-like cytotoxicity.
Project description:Virtual memory T (TVM) cells are a T-cell subtype that exhibit a memory phenotype without prior exposure to a foreign antigen. Although several recent studies suggest that TVM cells exert anti-viral and anti-bacterial function, pathological roles of TVM cells causing inflammatory diseases have not been studied. Here, we identified a novel CD8+ T-cell subset (CD44s-hiCD49dlo CD8+ T cells), which is originated from TVM cells and can cause a chronic inflammatory disease, alopecia areata (AA). In the skin of alopecic mice, we detected a distinct TVM-cell subpopulation characterized by superior expression of CD44 and features of tissue residency, which was transcriptionally, phenotypically, and functionally distinct from conventional CD8+ TVM cells. Mechanistically, this cell population could be induced from conventional TVM cells by IL-12, IL-15, and IL-18 stimulation. Moreover, the pathological activity of CD44s-hiCD49dlo CD8+ T cells was mediated by NKG2D-depedent innate-like cytotoxicity against target cells, which was further augmented by IL-15 stimulation and triggered the onset of disease. Collectively, our results suggest a new immunological mechanism through which TVM cells can cause chronic inflammatory disease by innate-like cytotoxicity.
Project description:Virtual memory CD8+ T (TVM) cells are a distinct subset of antigen-inexperienced cells with rapid effector potential, but their regulatory checkpoints remain elusive. Here, using bulk RNA sequencing, we found that DUSP2 intrinsically limits the differentiation of highly activated TVM cells, thereby constraining antiviral immunity.