To examine the role of NFAT1 and NFAT2 in CD8+ T cell differentiation during acute viral infection, we used mice deficient in NFAT1 (NFAT1−/−, referred as NFAT1 KO) and mice with conditional T cell-specific deficiency of NFAT2 (NFAT2fl/fl CD4-Cre+, referred herein as NFAT2 TKO). Here, CD4 is linked to viral infectious disease.