Contrasting impairments in IgM and IgG responses of vitamin A-deficient mice

Mice fed a semipurified, vitamin A-deficient diet (A- mice) and control animals fed the same diet with added retinyl acetate (A+ mice) were used to investigate the effect of vitamin A deficiency on primary immunoglobulin responses to protein antigens. At age 6 weeks, A- mice had serum retinol concentrations that were 46% of A+ controls. When immunized with a single antigen dose, these mice produced an antigen-specific IgM response equivalent to controls, but their IgG1 and IgG3 responses were sharply diminished (less than 30% of A+ controls). At age 8 weeks, A- mice had 20% of A+ serum retinol concentrations and less than 17% of A+ liver retinyl palmitate levels. Responding to a single antigen dose, A- mice produced approximately equal to 70% as much IgM as A+ controls. Their IgG1 response was less than 30% and their IgG3 response less than 3% of A+ controls. The IgG1 response kinetics were identical in A- and A+ mice. Diminished serum antibody responses in A- mice were attributable to fewer immunoglobulin-secreting plasma cells rather than to a decline in IgM or IgG secretion rate per cell. Total serum IgG3 levels, irrespective of antigen specificity, were slightly elevated in A- mice compared to A+ controls. The inefficient clonal expansion of responding B lymphocytes and contrasting impairment of IgM and IgG responses observed in vitamin A-deficient mice are discussed with respect to a possible helper/inducer-T-lymphocyte defect.