Chronic zinc deficiency in rats: Its influence on some parameters of humoral and cell-mediated immunity

The effect of dietary zinc deficiency on immune function was studied in specific pathogen-free rats. The spleen cell response to sheep red blood cells (srbc) and serum hemolysins were measured in rats maintained on the depleted or normal diet for periods of time ranging from 3 to 10 weeks and immunized with srbc six days prior to sacrifice. The in vitro response of splenic lymphocytes to the polyclonal T-cell mitogen, phytohemagglutinin (PHA), was also investigated. There was no significant effect of the diet on spleen plaque-forming cells, although values for zinc-deficient rats tended to vary widely as the time on the diet increased. Hemolysin titers were unaffected by diet at all intervals. A significant reduction in lymphocyte blastogenesis was observed in the zinc-deficient rats after 5 weeks on the diet. Control animals responded with four times the stimulation observed in the low zinc group. Thymus weight and serum zinc levels were significantly reduced by the zinc-deficient diet. Chronic, moderate zinc deficiency appears to have a differential effect on humoral and cell-mediated lymphocyte functions in this model. The normal plaque-forming cell and hemolytic antibody response to srbc suggests that helper T-cell and B-cell functions are intact. In contrast, the impaired mitogenesis in response to PHA stimulation indicates that zinc deficiency is affecting other T-cell subset(s).