FIG. 4.

Secreted Ipa proteins from S. flexneri in vitro. (a) Secreted Ipa proteins in response to different stimuli. Lanes 1, 3, 5, and 7, M90TS; lanes 2, 4, 6, and 8, Sh42; lanes 1 and 2, unactivated controls; lanes 3 and 4, Congo red-activated samples; lanes 5 and 6, fibronectin-activated samples; lanes 7 and 8, laminin-activated samples. IpaB and IpaC are indicated by arrows, and molecular mass markers are indicated. (b) Kinetics of the secretion of Ipa proteins in response to Congo red. Lane 1, secreted Ipa proteins from M90TS at 30 min; lanes 2, 3, 4, and 5, secreted Ipa proteins from Sh42 at 30, 60, 90, and 120 min, respectively; lanes 6 and 7, cell-associated Ipa proteins from M90TS and Sh42, respectively. (c) Semiquantitation of the secreted Ipa proteins shown in panel b (lanes 1 to 5) by image densitometry.