The vast majority of i. p. injected BCG is associated with mononuclear cells in CBA (A), but with PMN in CBA/N (B) mice, as demonstrated by auramine staining for mycobacteria with Gimsa counterstaining of cytospin preparations. Before challenge, BCG-vaccinated mice of the two strains did not differ by numbers of IFN-γ-producing CD4+ T cells in their lungs (C), but at week 3 post-infection the number of these cells in the lungs of the w. t. CBA mice was ~4 times (P < 0.01, Mann-Whitney U-test) higher (D). In the spleen, the numbers of IFN-γ-producing T cells differed ~10-fold (P < 0.001) after BCG vaccination in the absence of challenge (E). Magnetically sorted CD4+ lung T cells (C and D) or bulk spleen cells (E) from 3 individual mice in each group were analyzed using the ELISPOT assay; the results of one of two similar experiments are presented as mean ± SD. Neutrophil depletion prior to BCG vaccination resulted in significant (P < 0.01, Mann-Whitney U-test) ~8-fold reductions in CFU counts in lungs (F) and spleens (G) compared to control groups.