Effect of increased circulating corticosterone in the immature fowl on the blastogenic responses of peripheral blood lymphocytes.

Plasma corticosterone concentrations were increased by giving chickens implants containing corticosterone and the effects on lymphocyte numbers and lymphocyte responses to the mitogens, phytohaemagglutinin (PHA) and concanavalin A (con A), were measured. Raising plasma corticosterone caused a dose-related decrease in numbers of circulating lymphocytes. Blastogenic responses of lymphocytes in whole blood to PHA and con A were reduced and stimulation indices were decreased in those birds with raised circulating corticosterone. When the initial corticosterone-induced lymphocytopenia was taken into account it was evident that corticosterone depressed the responsiveness of the lymphocytes to PHA but not to con A. Additions of corticosterone to cultures of whole blood showed that PHA stimulation was more sensitive than con A stimulation to the inhibitory effects of corticosterone.