Expression of MHC-I and II by microglia and lymphocytes in the brain of diet-restricted mice

Abstract

Microglia are immunocompetent cells of the central nervous system whose function is to preserve nervous tissue homeostasis; however, under inflammatory conditions, they are associated with tissue damage. Dietary restriction is a nutritional intervention used to delay the onset of chronic disease and inflammation, in addition to improving the functions of the immune system. The aim of this study was to analyze the effect of dietary restriction on microglial expression of MHC molecules. Adult female and male BALB/c mice were fed ad libitum (controls) or kept under dietary restriction (30% reduction in food intake) for 4 wk. Purified brain mononuclear cells were analyzed by flow cytometry staining for CD45, CD11b, MHC-I and MHC-II. Our results show that female animals under dietary restriction had a significant increase in MHC-I expression in microglia (mean fluorescence intensity=7,854 (control) vs. 10,628 (diet-restricted), arbitrary units; p=0.0108), along with increased frequencies of lymphocytes compared to controls (1.39% (control) vs. 7.85% (diet-restricted); p=0.0175), whereas male animals did not show significant differences between groups. Our data suggest a differential effect for dietary restriction on female and male animals, with this nutritional regimen predominantly affecting females. Increased expression of MHC-I by diet-restricted microglia may play a role in maintaining tolerance in the absence of antigenic stimulation.