Alloimmunization-induced changes in β-adrenoceptor expression and cAMP on B lymphocytes

Abstract

In this report we have examined the effect of alloimmunization on β-adrenergic expression in lymphocytes. We have observed a variation in the number of β-adrenoceptors (Bmax) according to the degree of immunization without modifications in their affinity (Kd). This phenomenon was accompanied with parallel variations of intracellular cAMP levels. A decrease in Bmax values was observed during the first and second immunizations. Then the Bmax began to increase, exceeding control values up to the fourth and fifth immunizations, and remaining constant at the sixth immunizations. Only B cell-enriched populations showed variation in Bmax values of β-adrenoceptors with alloimmunization. In contrast, the Bmax values of T cell-enriched populations did not change. Kd values were similar in all cell types tested. The number of binding sites was not dependent on the animal's age. Modifications in cAMP levels of B cell-enriched populations were correlated with changes in β-adrenoceptor expression. These results suggest that β-adrenoceptor expression and cAMP intracellular levels in B cell-enriched populations vary with the number of alloimmunizations. In addition, the antibody synthesis induced by allogenic stimulus was inversely proportional to the number of β-adrenoceptors expressed on B cells. Perhaps these findings are evidence of a control mechanism that regulates antibody synthesis during the immune response.