Modifications of cell-mediated immune responses by moderate dietary protein stress in immunologically immature and mature BALB/c mice.

Female BALB/c mice at 5, 6 (immature) and 35 weeks of age (mature) were placed on isocaloric control (20% protein) or experimental (4% protein) diets. Cell-mediated immune responses [theta-bearing cell percentages, phytohemagglutinin (PHA) induced mitogenesis, mixed lymphocyte reaction (MLR) and antibody-dependent lymphocyte-mediated cytotoxicity (ADLMC)] of splenic lymphocytes were measured. A significant decline in percentages of theta-bearing cells, PHA and MLR responses occurred as early as two weeks for the immature mice on the restricted diet and continued for up to 8 weeks. In mature mice, protein restriction did not influence theta-bearing cell percentages, but did suppress PHA and MLR responses between 7 and 13 weeks. A significant suppression of ADLMC responses were also noted at 16 weeks. These results indicate that developing cellular immune systems of immature BALB/c mice are more sensitive to moderate protein restriction (i.e. immunosuppression occurs after a shorter interval) than those of mature mice. They suggest that moderate protein malnutrition retards but does not prevent immunological maturation.