Migration of bone marrow lymphocytes demonstrated by selective bone marrow labeling with thymidine‐H³

Abstract

Abstract Thymidine‐H 3 was injected into the femoral and tibial marrow (labeled marrow) of guinea pigs while the hind limb circulation was arrested temporarily and non‐radioactive thymidine was administered systemically. Blood and lymphoid tissue radioautographs were subsequently examined for the presence of marrow‐derived labeled cells. Small lymphocytes in the labeled marrow showed a wave of labeling, maximal at two to three days. Concurrently, labeled small lymphocytes appeared in the blood and lymphoid tissues, mainly the spleen and mesenteric lymph node. Their numbers were greatest at four to five days, and declined rapidly thereafter. At first they appeared predominantly in the splenic red pulp and throughout the lymph node cortex, including the subcapsular sinus. By four to five days they were also concentrated in the splenic white pulp, including periarteriolar lymphoid sheaths, and in the lymph node medullary cords. They were detected within medullary sinuses, hilar lymphatics and thoracic duct lymph. Labeled monocytes and large lymphoid cells also appeared in the blood and lymphoid tissues, mainly in the spleen. It is concluded that bone marrow is a major source of circulating newly‐formed small lymphocytes many of which migrate rapidly into the spleen and mesenteric lymph node.