Impaired immunity in vitamin A-deficient mice.

Vitamin A deficiency was produced in mice and was used to investigate the role of vitamin A in immune function. Cellular immunity, as measured by delayed-type hypersensitivity, diminished in early deficiency before weight and appetite changes occurred and declined further as the deficiency progressed. Humoral immunity, as measured by serum immunoglobulin M (IgM) responses to a protein antigen (hemocyanin), also declined. The kinetics of antibody production were unaffected by the deficiency. The T-cell number remained unchanged, but B-cell and macrophage numbers were increased in vitamin A--deficient mice. Surface expression of membrane glycoproteins (Thy-1, Lyt-1, Lyt-2, L3T4, IgM, Mac-1) was unchanged by the deficiency, as were lymphocyte numbers and distribution. The results suggest that vitamin A deficiency is associated with a functional immune system defect.