Immune response in mice and effects on cells by outer membrane porins from Salmonella typhimurium.

In this study, we describe the role of porins extracted from the outer membrane of S. typhimurium on the interaction with the host organism. The tests were performed on CD-1 mice immunized both with whole S. typhimurium cells and with purified porins. The antibody titres obtained in mice treated with purified porins and in those treated with whole Salmonella are 1/320 and 1/80 respectively. Cell-mediated response was found to be stimulated in both mice groups: our results show that T lymphocytes determine an increase in H3-thymidine incorporation and MIF production. An increase in lymphocytes with membrane immunoglobulins was observed in the lymphocyte population from the spleens of the treated mice. Purified porins added to macrophages cultures exerted a toxic effect at concentrations between 10 and 20 micrograms/ml. Subinhibiting concentrations (5 micrograms/ml) led to modifications in the surface tension of macrophages layers adhering to the slides. Moreover, subinhibiting porins concentrations were found to modify macrophage functionality as shown by evaluation of the phagocytic index and of intracellular killing, both of which were found to have diminished with respect to controls. When purified porins were added in vitro to populations enriched with T and B lymphocytes, at concentrations between 1 and 5 micrograms/ml they were found to be mitogenic with respect to B lymphocytes. The results we obtained showed that lymphocytes with IgM increase in porins tests. Eventually, purified porins added to Hela and Hep-2 cells were shown to exert a toxic effect which became detectable in the final concentration of 5 micrograms/ml and 1 micrograms/ml for Hela and Hep-2 cells respectively.