FIG. 1.
Suppression of PHA-induced proliferation by whole-cell S. typhi and STF. PBMC were cultured in the presence of PHA (2 μg/ml) alone or with STF (4 μg/ml), whole-cell S. typhi (2 × 105 particles per well), or LPS (10 ng/ml) for 3 days. Proliferation was determined by incorporation of tritiated thymidine. The data are expressed as mean percent suppression (standard deviation [SD]) of PHA-induced proliferation in four volunteers vaccinated with the S. typhi Ty21a typhoid vaccine (A) or four unvaccinated individuals (B) evaluated in two independent experiments with similar results. ∗, P < 0.05 compared to PHA-stimulated cells.