CD40 and infection: There was no discernible difference in the proportions of lung macrophages according to route of infection, but there was a reduction in macrophages in the placebo animals compared to survivors (median value of 5%, range 0.6 to 9%, compared to a median of 12.5%, range 0.6 to 23.5%, P < 0.0001), but a mean increase of 38% in CD40+ expression (classical phagocytic activation) on the few present (P < 0.0001).