Lymphocyte trapping. Differential effects of ATS and irradiation on trapping in lymph nodes and spleen.

Increased sequestration (trapping) of lymphocytes occurs in lymphoid organs following antigenic challenge. The effects of irradiation and anti-thymocyte serum (ATS) upon lymphocyte trapping in lymph nodes and spleen were studied. Both the above agents diminished or abrogated trapping in the draining lymph nodes; these same agents resulted in enhanced trapping in the spleen. Suppression of lymph node trapping could be achieved with a low dose of ATS and with 850 R, but not 200 R. These results are interpreted as showing that lymphocyte trapping in lymph nodes is initiated primarily by an ATS- and irradiation-sensitive population, whereas in the spleen a cell population resistant to the above agents activates the lymphocyte trap. These data demonstrate that the cell populations and/or the mechanisms involved in lymphocyte trapping in lymph nodes and spleens are distinct.