In vivo apoptosis in Shigella flexneri infections.

Shigella flexneri, an etiological agent of bacillary dysentery, causes apoptosis in vitro. Here we show that it also induces apoptosis in vivo. We were able to quantify the number of apoptotic cells in rabbit Peyer's patches infected with S. flexneri by detecting cells with fragmented DNA. Infection with virulent S. flexneri results in massive numbers of apoptotic cells within the lymphoid follicles. In contrast, neither an avirulent strain nor an avirulent strain capable of colonizing Peyer's patches increases the background level of apoptotic cells. Macrophages, T cells, and B cells are shown to undergo apoptosis in vivo. These results indicate that apoptosis may play a crucial role in the pathogenesis of shigellosis.