SUPPRESSION OF MAJOR HISTOCOMPATIBILITY COMPLEX CLASS-I AND CLASS-II GENE-EXPRESSION IN LISTERIA MONOCYTOGENES-INFECTED MURINE MACROPHAGES

Macrophage cells play a central role during infection with Listeria mo nocytogenes bq both providing a major habitat for bacterial multiplica tion and presenting bacterial antigens to the immune system. In this s tudy, we investigated the influence of L. monocytogenes infection on t he expression of MHC class I and class II genes in two murine macropha ge cell lines. Steady-state levels of I-A beta chain mRNA were decreas ed in both resting J774A.1 and P388D(1) macrophages infected with L. m onocytogenes whereas reduction of H-2K mRNA was only observed in P388D (1) cells. In addition, L. monocytogenes suppressed induction of MHC c lass I and class II mRNAs in response to gamma-interferon as well as t he maintenance of the induced slate in activated P38SD(1) macrophages. Exposure to the non-pathogenic species L. innocua or a deletion mutan t of L. monocytogenes, which lacks the lecithinase operon, did not cau se a reduction in H-2K and I-A beta mRNA levels nor suppress expressio n of Ia antigens. Inhibition of MHC gene expression may represent an i mportant part of the cross-talk between L. monocytogenes and the macro phage that probably influences the efficiency of a T cell-mediated imm une response and thus the outcome of a listerial infection. (C) 1998 F ederation of European Microbiological Societies. Published by Elsevier Science B.V.