The Radiation Resistance of Long-Lived Lymphocytes and Plasma Cells in Mouse and Rat Lymph Nodes

Abstract

Summary Rats and mice were given a secondary immunologic stimulus with typhoid-paratyphoid A and B vaccine and then were given twice daily injections of tritiated thymidine for 4 days into the hind footpad. Thirty days later the mice were exposed to 850 rad, 500 rad or were left nonirradiated, and the rats were exposed to 850 rad or left nonirradiated. Despite a marked, generalized destruction of lymphocytes, the aortic nodes of the mice and the popliteal nodes of the rats had larger values for per cent of small lymphocytes labeled in the period immediately following irradiation than did the nodes from the nonirradiated control animals. The mean grain counts of the labeled small lymphocytes from irradiated animals were equal to or larger than those from nonirradiated animals. These results are interpreted as demonstrating a relative radioresistance of long-lived, lymph node lymphocytes. Large numbers of persistently labeled plasma cells were also found in lymph nodes after irradition. No difference could be found in the numbers or distribution of labeled plasma cells in lymph nodes from irradiated mice compared to lymph nodes from nonirradiated mice. There may have been a loss of a small proportion of the long-lived plasma cells present in the rat lymph nodes. We believe the ability of plasma cells to survive irradiation explains the radio-resistance of established antibody production.