Cell-specific intracellular cytokine production by adult MNC in response to GBS or PHA. PBMC were stimulated for 0, 6, 24, and 48 h with either PHA or HKGBS (1 × 108 CFU/ml), brefeldin A was added for the last 4 h of stimulation at each time point, and cells were stained for cytokine and cell lineage markers. Data shown are means ± SEM (n = 4 donors).