Observations on the Nature of Hormone‐induced Eosinopenia

SUMMARY The possible causes for the disappearance of eosinophils from the peripheral blood following the administration of certain adrenal steroid hormones are reviewed. A series of experiments was performed in which the number of circulating eosinophils was determined at regular intervals following the intravenous administration of either ACTH or hydrocortisone. The results of these experiments show that under these circumstances the rate of disappearance of eosinophils is approximately constant. In no instance was the rate of disappearance described by an exponential function. It is claimed that this constant rate of disappearance implies an inhibition of the production or delivery of eosinophils by the bone marrow to the peripheral blood ; and that those cells in the circulation fulfil their normal physiological life span. The points in time at which the eosinopenic reaction is maximal have been determined. It is claimed that these represent estimates of the life span of eosinophil leucocytes. The range of such estimates is from 165 to 377 minutes. Other methods used to estimate the survival of leucocytes, in general, and eosinophils, in particular, are discussed in the light of these present observations.