1. Pituitary adrenocorticotrophic hormone (ACTH), when administered in a single intramuscular dose of 25 mg. to human subjects with unimpaired adrenal function, results in a characteristic alteration of the leukocytic pattern. This consists of an increase of circulating neutrophils and a decrease of circulating lymphocytes and eosinophils.
2. The decrease in circulating lymphocytes and eosinophils is contingent upon the stimulation of a functionally competent adrenal cortex, and does not occur in its absence. The neutrophilic response is present but somewhat diminished in adrenal insufficiency.
3. The entire pattern of leukocytic alterations found in normal subjects after administration of ACTH can be induced in patients with Addison’s disease by 17-hydroxycorticosterone (20 mg.) but not with desoxycorticosterone glucoside (30 mg.).
4. Prolonged adrenal stimulation by ACTH, given over a four day period in a dose of 10 mg. every six hours, results in a sustained and striking elevation of neutrophils and depression of eosinophils; the lymphocytes, after an initial depression lasting not more than twenty-four hours, may increase above their initial levels in spite of the continued increased secretion of adrenal hormones.
5. The relation of the adrenal cortex to the characteristic nonspecific leukocyte pattern, observed as a response of the organism to any type of insult, is discussed.
ACKNOWLEDGEMENTS We are indebted to Mrs. Elizabeth Dell, B.S., Mrs. Constance Forsham, B.S., M.T. (A.S.C.P.), and Miss Loretta Conroy, B.S., for their technical assistance, and to Miss Mary Kascht, B.A., Research Dietitian, who kindly took over the secretarial management in addition to the dietary work.