Studies on lymphocytes. I. Lymphopenia produced by prolonged extracorporeal irradiation of circulating blood.

T HERE ARE numerous conflicting concepts in respect to the function, fate and life span of lymphocytes.15 Radiation of segments of the wholebody or of lymphocytes in vitro has long been exploited in the study of lymphocytes.69 However, irradiation of the whole-body or segments injures lymphopoietic tissue and the in vitro environment separates the lymphocyte from homeostatic influences. We reasoned that if it were possible to destroy large numbers of circulating lymphocytes by irradiation of the circulating blood in an extracorporeal shunt under controlled conditions and without direct radiation of lymphopoietic tissues, we might be able to study many facets of lympho-