Malnutrition and humoral immunity: long-term protein deprivation.

The effect of long-term protein deprivation and refeeding on delayed-type hypersensitivity (DTH) and humoral immune function was investigated in rats. Animals previously sensitized to keyhole limpet hemocyanin (KLH) were placed on a 2% protein diet ad lib for 8 weeks, after which some groups of animals were refed for up to 4 weeks. Control rats received normal rat chow. Recall skin testing with KLH, and immunization with tetanus toxoid (TT) were used to assess DTH and humoral immune responses. Weight, DTH, and antibody responses declined progressively with protein deprivation. Refeeding restored skin test responses and humoral immunity. There was a direct correlation between degree of malnutrition as reflected by weight and antibody responses as well as between DTH and antibody responses. The data demonstrate that chronic protein deprivation modulates both DTH skin testing and humoral immune responses and show that under conditions of altered immune function, there is a correlation between DTH responses and humoral immune function.