LPS induces the autocrine secretion of TNF-, which produces apoptosis.

(A) LPS induces the mRNA expression of TNF-α. Total RNA (20 μg per lane) from macrophages was treated with 100 ng/mL of LPS for the indicated times was analyzed by Northern blotting. (B) LPS induces the secretion of TNF-α. The concentration of TNF-α in the culture supernatants was analyzed by ELISA. Each experiment was performed 3 times and represented as the mean value ± SD. (C) TNF-α induces apoptosis in bone marrow macrophages. Macrophages were stimulated for 12 hours with the indicated concentrations of rmTNF-α. Induction of apoptosis was measured by ELISA. (D) Time course of rmTNF-α–induced apoptosis. Macrophages were treated with rmTNF-α (100 ng/mL) for the indicated periods of time. Each experiment was performed in triplicate and represented as the mean ± SD, and 1 of 3 independent experiments is shown in this figure.