CD8A and infection: Surprisingly, CD8 T cells and macrophages were also detected in the brains of mice immunized with 107 IrrPb on day 6 after challenge, and their frequencies were not significantly different from those observed in naïve mice during infection (Figure 6B, 107 IrrPb Challenged, solid black and hatched bars, 3.3+/−0.2% and 2.0+/−0.6% of isolated cells, respectively).