Both wild-type and mutant bacteria trigger secretion of IL-1β and IL-8 from mononuclear phagocytes. MDM (A and B) and monocytes (C) were infected with LVS, the carA mutant (5H9), the carB mutant (3E10), or the single-iglC mutant (9H5) as described in Materials and Methods, and at 24 hpi, the amount of mature IL-1β (A and C) or IL-8 (B) present in the tissue culture medium was quantified by ELISA. In each case, error bars indicate the means ± standard errors of the means of the results for triplicate samples from one experiment that is representative of three. Uninf, uninfected.