PRF1 and infection: Differential gene expression analysis also found that the signal of T cell exhausting markers, such as CTLA-4 (Ctla4) and Tim3 (Harvcr2), as well as granzyme B (Gzmb) and perforin (Prf1) were significantly downregulated in effector CD8+ T cells at the recurrence stage, as compared to the acute infection stage (Figure 4H).