NFAT2 Regulates Generation of Innate-Like CD8(+) T Lymphocytes and CD8(+) T Lymphocytes Responses

Nuclear factor of activated T cells (NFAT) 2 null mutant mice die in utero of cardiac failure, precluding analysis of the role of NFAT2 in lymphocyte responses. Only the NFAT2(−/−)/Rag-1(−/−) chimeric mice model gave insight into the role of NFAT2 transcription factor in T lymphocyte development, activation, and differentiation. As reports are mainly focused on the role of NFAT2 in CD4(+) T lymphocytes activation and differentiation, we decided to investigate NFAT2’s impact on CD8(+) T lymphocyte responses. We report that NFAT2 is phosphorylated and inactive in the cytoplasm of naive CD8(+) T cells, and upon TCR stimulation, it is dephosphorylated and translocated into the nucleus. To study the role of NFAT2 in CD8(+) T responses, we employed NFAT2(fl/fl)CD4-Cre mice with NFAT2 deletion specifically in T cells. Interestingly, the absence of NFAT2 in T cells resulted in increased percentage of non-conventional innate-like CD8(+) T cells. These cells were CD122(+), rapid producer of interferon gamma (IFN-γ) and had characteristics of conventional memory CD8(+) T cells. We also observed an expansion of PLZF(+) expressing CD3(+) thymocyte population in the absence of NFAT2 and increased IL-4 production. Furthermore, we found that CD8(+) T lymphocytes deficient in NFAT2 had reduced activation, proliferation, and IFN-γ and IL-2 production at suboptimal TCR strength. NFAT2 absence did not significantly influence differentiation of CD8(+) T cells into cytotoxic effector cells but reduced their IFN-γ production. This work documents NFAT2 as a negative regulator of innate-like CD8(+) T cells development. NFAT2 is required for complete CD8(+) T cell responses at suboptimal TCR stimulation and regulates IFN-γ production by cytotoxic CD8(+) T cells in vitro.