This phenotype was confirmed by a significant increase of T-bet+CD44+ Th1 cell proportion, as well as IFN-γ-secreting activated CD4 T cells, among CD4 T cell population in IFNAR KO mice; however, the levels of CD4 T cell subsets were similarly decreased in both wild type and the mutant mice, potentially via cellular apoptosis, as we observed in scrub typhus patients previously (Figures 4B,C and Table S2) (20). Here, CD4 is linked to scrub typhus.