Influence of dietary protein restriction on the delayed-type hypersensitivity response to sheep red blood cells in mice.

Delayed-type hypersensitivity responses to sheep erythrocytes were studied in inbred C57BL/6 and outbred NMRI mice fed either protein-deficient diets containing 8% and 4% casein or a normal diet with 27% casein. Following sensitization with optimal doses of antigen, the magnitude of the response was similar in mice fed the 8% protein and the normal diet. Large numbers of sheep red blood cells which suppressed the delayed hypersensitivity response in normal mice, failed to inhibit this response in animals fed the 8% casein diet. However, the titres of serum haemagglutinins were similar in mice of either dietary group immunized with high doses of antigen. Sensitized spleen cells from deficient mice kept on the 8% casein diet, had lower suppressor capacity than those from normal mice upon transfer into syngeneic hosts. Delayed-type hypersensitivity was significantly depressed in mice fed the 4% protein diet whereas the titres of serum antibodies to sheep erythrocytes were not diminished.