ADHESION, INVASION AND INTRACELLULAR REPLICATION OF SALMONELLA-TYPHIMURIUM IN A MURINE HEPATOCYTE CELL-LINE - EFFECT OF CYTOKINES AND LPS ON ANTIBACTERIAL ACTIVITY OF HEPATOCYTES

Elimination of pathogenic microorganisms in the liver may be an import ant effector mechanism in host defenses. in this paper we describe the adhesion, invasion and multiplication of Salmonella typhimurium in a murine embryonic hepatocyte cell line (ATCC TIB-73). Monolayers of hep atocytes treated with recombinant IFN gamma, IL1 beta, and LPS exhibit antibacterial activity against intracellular Salmonella. The dynamic of the infection process in stimulated vs unstimulated hepatocytes was determined by counting the number of survival bacteria in the cell mo nolayers at 4 and 28 h after gentamicin was added to the infected cell s. Salmonella typhimurium is able to adhere, invade and replicate insi de the hepatocytes. The maximum number of cell-associated bacteria is approximately 15 bacteria per cell, whereas the invasive capacity of S almonella is 0.003 bacteria per hepatocyte. Stimulated cultures displa y antibacterial activity compared to unstimulated controls. The antiba cterial activity does not seem to be mediated by nitric oxide (NO) sin ce inhibition of NO production by using N-G-Monomethyl-L-Arginine did not revert the antibacterial activity. Also, high amounts of NO induce d by adding L-Arginine to the cell cultures did not enhance hepatocyte antibacterial activity. (C) 1996 Academic Press Limited