FIG. 1.

Cytotoxic activity in S. flexneri culture supernatants and infected macrophages. (A) Culture supernatants of S. flexneri type 1A-infected J774 macrophages (black bar) and S. flexneri type 1A alone (striped bar) contain similar levels of cytotoxic activity. The culture supernatants of macrophages alone (white bar) were noncytotoxic. (B) Time course of the cytotoxic activity in commercial S. flexneri type 1A LPS preparations. THP-1 cells were incubated with 10 μg of S. flexneri type 1A PW-LPS (open squares) or TCA-endotoxin (open circles) per ml and assayed for cytotoxicity at the indicated time points. Percent cytotoxicity was determined by an LDH release assay.