CD4 and infection: Intriguingly, while microglia promote IFN-γ production by CD4+ T cells (Fig. 5c, d), they do not express I-A/1-E (MHC-II) or H2-Aa, H2-Ab1, H2-DMa and H2-Eb1 (MHC-II molecules) during infection (Fig. 6a, f).