Groups of IFrag−/− mice were intratracheally inoculated with either 107, 105, 103 live Pneumocystis (PC) nuclei, or 107 dead PC nuclei and bone marrow responses compared to animals either inoculated with clean lung homogenate at day 16 post infection and uninfected animals. Figure 3A shows Pneumocystis (PC) lung burden at day 16 post infection following microscopic enumeration. Figure 3 B shows total bone marrow counts of all IFrag−/− comparison groups at day 16 post infection. Antibiotic treatment was initiated in groups of IFrag−/− mice three days prior to (day -3) and at day 0, 3 and 7 post inoculations with 107 PC nuclei. Bone marrow cell numbers and PC lung burden were evaluated and compared to uninfected mice at day 16 post infection. Figure 3C shows PC lung burden and Figure 3D shows total bone marrow counts at day 16 post infection. Statistical analysis was performed using a 1-way ANOVA. All groups were compared to those mice receiving 107 PC nuclei. P values are marked as * p< 0.05, ** p<0.01, *** p<0.001.