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.