CD4 and infection: When we compared the expression of CD84 on T cells in lung and spleen tissue taken from mice in the above-described experiment after infection with M. tuberculosis for 30 or 60 days to its expression in uninfected control mice, we found that CD84 mRNA levels (determined by qPCR) were significantly higher in CD4+ and CD8+ T cells in both tissues after M. tuberculosis infection (Fig. 2a).