In vitro study of Listeria monocytogenes infection to murine primary and human transformed B cells.

Immunity to Listeria monocytogenes is largely mediated by T lymphocytes. Recently, B lymphocytes or their secreted products are implicated to provide immunity against L. monocytogenes infection. To understand whether L. monocytogenes can infect and kill B cells as a possible strategy to initiate an infection, we examined the effects of L. monocytogenes on a human B lymphoma (Ramos RA-1) and mouse primary B cells in vitro. L. monocytogenes infection resulted in significantly (p<or=0.05) high cytotoxicity (58-79%) for Ramos and 39-68% cytotoxicity for mouse primary B cells. In contrast, non-pathogenic L. innocua caused only 1.2% cytotoxicity for Ramos and 19% for primary B cells. Bacterial cells were found frequently adhered to the B cell surfaces; however, active invasion was not a prerequisite for infection. L. monocytogenes caused loss of B cell surface molecules, pore formations, cell swelling, membrane damages and apoptosis. This study demonstrates that L. monocytogenes can infect and kill B cells as a possible strategy to initiate a successful infection.