FIG. 6.

Cytokine induction by the LT-IIb B pentamer is regulated by LT-IIb holotoxin. THP-1 cells were incubated for 16 h with medium only, LT-IIbB alone, LT-IIbB plus LT-IIb, or LT-IIb alone (all at 2 μg/ml). Culture supernatants were assayed for cytokine content by ELISA. Results are presented as means ± standard deviations of triplicate determinations. Cytokine responses in cells treated with both LT-IIbB and LT-IIb holotoxin that are statistically significantly different (P < 0.05) from those for treatment with LT-IIbB alone are indicated by asterisks.