INFECTION OF DIFFERENTIATED U937-CELLS BY SALMONELLA-TYPHIMURIUM - ABSENCE OF CORRELATION BETWEEN OXIDATIVE BURST AND ANTIMICROBIAL DEFENSE

The human histiocytic lymphoma cell line U937 can be induced to differentiate along the monocyte/macrophage pathway by either phorbol myristate acetate (PMA) or by the combination of retinoic acid (RA) and 1,25-dihydroxyvitamin D3 (VD). U937 cells treated with either PMA or RA/VD were able to phagocytose Salmonella typhimurium in the presence of non-immune human serum. However, only cells differentiated by RA/VD were capable of developing an oxidative metabolic burst in response to infection. Since the oxidative burst is considered to be a potent antimicrobial mechanism, we investigated its effect on S. typhimurium. The oxidative burst failed to affect either the viability or the multiplication of S. typhimurium suggesting that it plays only a minor role in the host defence against S. typhimurium.