Zinc and immunocompetence in protein-energy malnutrition.

Malnourished children have thymic atrophy which is reversed by zinc supplementation. To see if their defect in cell-mediated immunity was also associated with zinc deficiency ten children were skin-tested with Candida antigen on both arms. One test site was covered with local zinc sulphate and the other with placebo ointment. There was a highly significant increase in the typical delayed-hypersensitivity reaction at the site covered with zinc. The magnitude of the difference between the supplemented and unsupplemented arms correlated negatively with the plasma-zinc concentration. These data show that zinc deficiency is a cause of the immunoincompetence seen in malnutrition. The normal reactions of the zinc-supplemented side indicate that, of the many nutritional deficits of malnourished children, zinc deficiency specifically impairs the cell-mediated immune system. Local skin-testing with and without zinc may provide a measure of zinc status. Local application of zinc may enhance the reliability of tests to diagnose diseases such as tuberculosis in malnourished patients.