Infection of athymic mice with M. tuberculosis following transfer of splenocytes from euthymic mice. (A and B) Results for the lungs and spleen, respectively, of mice infected intravenously with approximately 106 CFU 21 days prior to harvest. Transfer of cells was carried out 24 h before infection. Data are the means ± the standard errors of the means for three to five mice. Mice received either no cells, total spleen cells, CD4 cells, or CD8 cells. All three groups of mice which received cells showed significantly reduced CFU counts compared to controls (P < 0.05 by Student’s t test).