Immune response in overnutrition.

Nutritional modulation of the immune response can be demonstrated both in nutritional deficiency and in obesity. A proportion of obese adolescents and adults showed a variable impairment of cell-mediated immune responses in vivo and in vitro and reduction of intracellular bacterial killing by polymorphonuclear leukocytes. Immunological changes correlated with subclinical deficiencies of iron and zinc, and therapy with these micronutrients for 4 weeks resulted in improvement in immunological responses. In genetically obese mice, the number of mononuclear cells and Thy 1.2-positive lymphocytes in the thymus and the spleen is less compared with that in lean controls. The plaque-forming antibody response is reduced. Natural killer cell activity is increased. Cytotoxic response of spleen cells of obese animals immunized in vivo was markedly lower than that of lean controls, whereas the same response after in vitro sensitization was normal. These data point to the importance of metabolic and nutritional factors in the pathogenesis of altered immunocompetence.