Differential effect of pancreatectomy on humoral and cell-mediated immune responses.

Cell-mediated immune reactions, such as allogenic skin-graft rejection and PHA or MLC responses, and antibody synthesis against different antigens (sheep erythrocytes, Brucella antigen, bovine serum albumin) have been evaluated in rats suffering from experimentally-induced diabetes and in age-matched sham-treated controls. Cell-mediated immune reactions are strongly depressed diabetic rats. The cellularity of the thymus and of thymus-dependent areas and the number of peripheral blood lymphocytes is significantly reduced in pancreatectomized rats. Moreover, the immunological recovery from heavy cortisonization is also greatly impaired. Daily treatment with insulin may prevent these immunological alterations. By contrast, antibody responses in diabetic rats are not quantitatively altered in respect to either the number of antibody producing cells in the spleen or the circulating antibody titres. The discrepancy between the abnormality of cell-mediated immune reactions in diabetic rats and their physiological capacity to synthetize antibodies suggests that the sensitivity to an insulin-deprived environment is present only in a definite, although yet undefined, subpopulation of lymphoid cells rather than in the whole lymphoid system.