Leucapheresis in Man. II. Changes in Circulating Granulocytes, Lymphocytes and Platelets in the Blood *

THE continuous withdrawal of leucocytes from 47 patients with non-haeiiiatological iicoylasms by the process of leucapheresis has been previously reported (Bierman, Kelly, Byron and Marshall, 1961). This report is an analysis of the changes in the granulocytes, lymphocytes and platelets in the same patients. The factors which govern the delivery of lcucocytes into the blood from the storage sites, and those which control thc ultimate destiny of these leucocytes, are poorly understood. The constancy of the circulating concentration of mature leucocytes, with rapid turiiovcr, indicates a delicate self-regulatory control. This homeostatic state is characteristic of all hacmatopoietic tissues and must also exist for other tissues in the normal, as well as in the pathological state. Consequently, a thorough understanding of the balancing mechanisms for the leucopoietic system should be of fundamental importance to the understanding of all growth processes. Leucocyte depletion in the haematologically normal subject is accompanied by an accclerated delivery of leucocytcs into the circulation (Bierman et al., 1961). Leucocytes arc tissue cells which are produced in, stored by, aiid delivered from extracircdatOry reservoirs into the circulation (Bicrnian, Kelly and Cordes, 195 5) . Therefore, changes in granulocytc and lymphocyte concentrations were studed during and following leucapheresis. The removal of mature lcucocytes from the blood was accomplished to detcrinine the composition of the reservoirs and the dynamics of the release of leucocytes into the circulating blood. Siiicc large numbers of platelets were also removed during leucapheresis, changes in them were also studied.