Vitamin A status and the immune response to pneumococcal polysaccharide: effects of age and early stages of retinol deficiency in rats.

Production of antibodies to pneumococcal polysaccharide from Streptococcus pneumoniae, type III was determined in young rats at different ages and stages of vitamin A deficiency. At 30, 35 and 45 d of age, serum retinol concentrations of vitamin A-depleted rats were 46, 35 and 9%, respectively, of the serum retinol concentrations of pair-fed controls. Specific antibody production was low at 30 d of age for both vitamin A-depleted rats and control rats. Between 30 and 45 d of age, antibody production increased considerably in normal rats; however, the response of vitamin A-depleted rats was only 22% (P less than or equal to 0.001) that of controls at 35 d of age and 8% that of controls (P less than or equal to 0.001) for 45-d-old rats. Lymphocyte populations were examined by flow cytometry. The numbers of immunoglobulin M- and immunoglobulin D-positive cells changed with age, but not as a result of dietary treatment. The numbers of total T cells or helper and suppressor T cell subsets did not differ with age or with vitamin A status. These studies showed that the normal antibody response to pneumococcal polysaccharide develops rapidly after 30 d of age in the rat, that this antibody response is impaired even during the early stages of vitamin A deficiency, and that impaired antibody production does not seem to be accompanied by quantitative differences in splenic lymphocyte populations.