FIG. 4.
Flow cytometric analysis showing distribution of human PBMC containing IL-1β and/or TNF-α induced by STF or TT. PBMC from a volunteer immunized with the attenuated Ty21a S. typhi strain were incubated for 5 h with methylamine plus monensin in the absence or presence of TT (2 μg/ml) (left) or STF (4 μg/ml) (right). Cells were then stained intracellularly for IL-1β and TNF-α. Cytograms showing the distribution of cells within the monocyte region containing either IL-1β (lower right quadrants), TNF-α (upper left quadrants), or both cytokines (upper right quadrants) are presented. The percentage of positive cells in each of the quadrants is shown. These results are representative of those observed with cells obtained from three different individuals, one unvaccinated and two immunized with the attenuated Ty21a S. typhi strain.