Polyclonal activation of murine B lymphocytes in vitro by Salmonella typhimurium porins.

Porins were prepared from the outer membrane of Salmonella typhimurium and consisted of three polypeptides with similar molecular ratios around 40 kDa, and isoelectric points around 4.7. They constituted potent polyclonal activators for murine B lymphocytes. The compounds were mitogenic towards splenic lymphocytes of lipopolysaccharide responder Balb/c, non-responder (C3H/HeJ), and athymic (Balb/c nu/nu) mouse inbred strains, as measured by 3H-thymidine incorporation into DNA. Furthermore, porin-activated B cells differentiated into immunoglobulin-secreting cells, as was measured by an ELISA test. The porins will be valuable in elucidating the molecular mechanism of lymphocyte activation in bacterial infections.