Figure 1.

Acid-sphingomyelinase-deficient mice are more susceptible to BCG infection. Wild-type (wt) mice and acid-sphingomyelinase-deficient (Asm^−/−) mice were intravenously infected with 10⁷ colony-forming units (CFU) of Mycobacterium bovis Bacillus Calmette-Guérin (BCG) for 1, 7, or 21 days. (A,B) Cryosections from liver tissues after 3 weeks of infection were stained with hematoxylin and eosin (H&E) and analyzed by light microscopy with a 20× lens. Arrows indicate granulomas. Pictures are representative of at least 3 independent experiments. The number of granulomas was determined by counting them in 10 serial sections. Shown is the mean ± SD of granuloma per section, n = 4, t-test. (C) The total number of BCG in liver tissue homogenates after 1, 7, or 21 days of infection was determined by CFU assays. (D) BCG inside liver tissues after 3 weeks of infection were visualized by Truant staining with a 100× lens. Scale bar = 50 µm. Shown are means ± SD of numbers of bacteria (C), n = 4, ANOVA, statistical significance was set as **** p < 0.0001, ** p < 0.01, * p < 0.05 or representative pictures of at least 3 independent experiments (D).