Beta-estradiol-induced decrease in IL-12 and TNF-alpha expression suppresses macrophage functions in the course of Listeria monocytogenes infection in mice

Mice treated with a contraceptive dose of beta-estradiol (E2) demonstrated changes in their macrophage (M phi) number and functions. While E2 increase d and decreased the M phi number in PBMC and PEC respectively, it enhanced the in vitro phagocytosis of FITC-labeled beads by both cells. E2 treatment also enhanced the phagocytic function of M phi as assessed by the in vivo carbon clearance assay. In contrast, the in vitro intracellular killing fun ction of adherent cells in peritoneal exudate cells (PEC) against Listeria monocytogenes decreased after E2 treatment. In line with the decrease in th e intracellular killing function, the E2-treated mice showed an impaired pr otection against L. monocytogenes infection. To clarify the mechanism of th e E2-mediated suppression of the protective response against L, monocytogen es infection, we next analyzed the cytokine expression by PEC in E2-treated L. monocytogenes-infected mice. On day 5 of the infection, the expression of IL-12, TNF-alpha and IL-10 by adherent PEC from the E2-treated mice was lower than that from the control-infected mice. The decrease in the cytokin e expression by adherent PEC of E2-treated mice coincided with the decrease of IFN-gamma expression, and the increase in the IL-4, IL-10 and TGF-beta expressions by non-adherent PEG. These results revealed two aspects of the effects of E2 on M phi. Even though E2 was found to enhance M phi phagocyto sis, the anti-bacterial function was suppressed. This suppression may be me diated by the inhibition of both IL-12 and TNF-alpha which play important r oles in the protective response against intracellular bacteria. (C) 1999 In ternational Society for Immunopharmacology. Published by Elsevier Science L td. All rights reserved.