Complement inhibitor(s) released from leukocytes: II. Evidence that lymphocytes release and produce an inhibitor of C2 activation

Abstract We have previously reported that mouse spleen and thymus cells in short term culture release an hitherto undescribed complement inhibitor that prevents the activation of C2. Here it is shown that the inhibitor is released by B lymphocytes and may be produced by lymphocytes. Release of the inhibitor takes place at 37 °C and in the presence of metabolic inhibitors, but not at 4 °C. Thus the release of the inhibitor could be related to the shedding of structures located on the lymphocyte membrane.