CD4 and infection: However, the numbers of antigen-experienced T cells accumulating in the brain trended lower in PMCA4−/− mice on day 7 of infection (compared with WT littermate mice) and intracerebral antigen-experienced CD4+ and CD8+ T cells expressed slightly (but significantly) lower levels of GrB in infected PMCA4−/− mice than in WT littermate mice (Fig. 7A–F, with gating strategy as shown in Additional file 1: Fig. S1).