Factors Influencing the Fate of 111indium-labelled Lymphocytes After Transfer to Syngeneic Rats

Thoracic duct lymphocytes were labelled in vitro with 111indium-oxine or 111indium-acetylacetone in order to follow their migration after i.v. injection into syngeneic rats. Under certain conditions both preparations produced results with quantitatively confirmed data obtained by other approaches to the physiological pattern of lymphocyte recirculation. However, three significant difficulties were identified: (1) chemical toxicity by minor contaminants of the preparation; (2) radiation damage indicated by a progressive impairment of the recovery of radioactivity from lymph nodes. A labelling concentration of 20 microCi/10(8) cells was the highest compatible with survival of most lymphocytes for 24 h in vivo as confirmed by autoradiography; (3) rapid loss of 111In in vivo found at labelling concentrations below 1 microCi/10(8) cells. By one week after the injection of lymphocytes labelled at 20 Micro/Ci/10(8) cells most of the 111In had been transferred from lymphocytes to non-recirculating radioresistant cells within the spleen and lymph nodes.