FIG. 4.

LT-IIbB is a more potent cytokine inducer than LT-IIaB or CTB. THP-1 cells were incubated for 16 h in the absence or presence of LT-IIaB, LT-IIbB, or CTB (all at 2 μg/ml) or with E. coli LPS (10 ng/ml; positive control). Induction of TNF-α, IL-1β, or IL-6 release in culture supernatants was assayed by ELISA. Results are presented as means ± standard deviations of triplicate determinations. Values that are statistically significantly different (P < 0.05) from those of medium-only-treated controls are indicated by an asterisk.