Analysis of Stat6 requirement for accumulation of macrophages during N brasiliensis infection. (A) Congenic mixed BM chimeras were generated with BM cells from wild-type (Ly5.1⁺) and Stat6^−/− (Ly5.1⁻) donor mice to analyze whether Stat6 expression in macrophages was required for survival and recruitment to the effector sites. The histogram demonstrates equal engraftment of both donor marrows at 8 weeks after reconstitution in the peripheral blood. (B) Peritoneal cells of naive mice (left dot plot) or of day 9 N brasiliensis-infected mice (right dot plot) that had been given BrdU for the past 36 hours were stained for F4/80, Ly5.1, and BrdU. Dot plots show F4/80-gated macrophages. (C-D) Macrophages in peritoneum (PEC), spleen (SP), BAL, and lung (LU) of wild-type (filled bars) and Stat6^−/− (hatched bars) mice that had been infected with N brasiliensis 9 days before (infected) or were left untreated (naive) were analyzed 36 hours after BrdU administration. Panel C shows the frequency of BrdU⁺ cells among total macrophages, and panel D shows the frequency of macrophages among total cells. Macrophages were identified by staining for F4/80 and CD11c (lung and BAL), F4/80 and CD11b (spleen), or F4/80 (PEC). The bars show mean ± SE of 7 individual mice from 4 independent experiments (**P ≤ .001; *P ≤ .05).