Apoptosis of Caco-2 intestinal cells invaded by Listeria monocytogenes: protective effect of lactoferrin.

The apoptosis of infected hepatocytes is a critical step in nonspecific defense against Listeria monocytogenes infection. We have observed that infection by L. monocytogenes in enterocyte-like cells (Caco-2) results in apoptosis. However, a large fraction of infected intestinal epithelial cells escape from cellular condensation and fragmentation, typical of programmed cell death, and become necrotic. The balance between apoptosis and necrosis seems to be influenced by the number of internalized bacteria. The presence of 1 mg/ml of bovine lactoferrin, an iron-binding protein, added to monolayers before the bacterial infection, decreases the number of internalized bacteria and therefore the overall number of dead cells, and, more importantly, all dead cells are killed by apoptosis and not necrosis.