Kinetics of mycobacterium-induced IL-8 secretion from U937 cells. (A) U937 cells were infected with M. tuberculosis (M. tbc) or M. marinum (MOI = 10) for 2 h. The cell culture supernatants were harvested 18, 48, and 96 h following infection, and IL-8 protein was measured by ELISA. Statistical differences were measured for cells infected with M. tuberculosis compared to cells infected with M. marinum. *, P < 0.05; **, P < 0.01. (B) Human monocytes and MDM were infected with M. tuberculosis or M. marinum (MOI = 10) for 2 h. IL-8 was measured by ELISA in the culture supernatants 48 (for MDM) or 96 (for monocytes) h following infection. The cells infected with M. tuberculosis and M. marinum were compared statistically. *, P < 0.05; **, P < 0.01. The error bars indicate SD.