However, mice depleted of CD8+ T-cells prior to secondary infection with P. murina had a significant increase in lung burden compared to either CD4-depleted or immune-intact animals at 2 and 4 days post-infection (DPI) (Figures 2A,B), despite similar amounts of Pneumocystis-specific IgG when compared to immune-intact animals. This evidence concerns the gene CD4 and infection.