Cell-mediated immunity in genetically obese C57BL/6J ob/ob) mice.

The thymus and spleen of genetically obese (C57BL/6J ob/ob) mice weighed less and contained fewer mononuclear cells and Thy 1.2-positive lymphocytes compared with findings in lean controls. The number of splenic antibody forming cells, particularly IgG-producing lymphocytes, was reduced. There was a marked increase in natural killer cell activity and a slight increase in antibody-dependent cell-mediated cytotoxicity in the obese animals. Cytotoxic response of spleen cells of obese mice immunized in vivo was markedly lower than that of lean controls, whereas the generation of T killer cells against alloantigens after in vitro immunization was unimpaired, which points to a deleterious "microenvironment" in obesity. It is suggested that metabolic, nutritional, and endocrine changes in obesity may contribute to altered immunocompetence.