Stimulation of primary human monocytes with superantigens enhances production of TNF-α in response to subsequent LPS challenge. Monocytes were exposed to 1 ng/mL SEB for 3 hours with coincubation with 1 ng/mL E coli LPS 0111:B4 for an additional 4 hours. (A) Composite box-plot to illustrate magnitude of enhanced induction of TNF-α by SEB-LPS (n = 10). ^*Denotes significant difference from “expected” cytokine production, derived from the sum of TNF-α produced from individual toxin stimulations; P = .002. (B) Enhancement of LPS-induced TNF-α production by SEB pre-exposure is restricted to the monocyte subset. Mean and SD of data from triplicate wells are shown. Data are representative of 3 separate experiments. (C) Enhanced production of TNF-α is not inhibited by neutralizing concentrations of anti–IFN-γ. ITMC indicates isotype-matched control antibody. Mean and SD of data from triplicate wells are shown. Results are representative of 3 separate experiments.