T and B lymphocyte function in response to a protein-free diet

Groups of female adult rats were fed either isocaloric protein-free or 18% protein diets for various intervals. Four days before sacrifice, the animals were immunized either with sheep erythrocytes or with a trinitrophenyl-lipopolysaccharide (TNP-LPS) conjugate. Spleen lymphoid cell populations, spleen plaque-forming cells, and serum hemolysins were measured. A persistent diminution, proportional to the duration of protein deprivation, was observed in all parameters studied after immunization with the T-dependent antigen, sheep erythrocytes. The immune dysfunction was more pronounced for hemolysin titers, which became undetectable after 15 days of protein-free diet. The response of the protein-free group to the T-independent antigen (TNP-LPS) after 15 days of diet was only 34% of the control. When a T-cell lymphokine, macrophage migration inhibitory factor, was measured, a normal response was observed in the protein-free group. Feeding a normal diet rapidly restored the spleen plaque-forming cell populations to 60% of normal after 4 days and to 100% after 6 days. Protein starvation influenced the production of antibodies more than it did the number of antibody-forming cells. The nutritional impairment of immunoglobulin synthesis appears to be reversible.