Further observations on transfusion collapse curves in inbred rats

Transfused allogeneic red blood cells (RBC) are very rapidly cleared from the host circulation in some strain combinations among inbred rats. The phenomenon, termed collapse curve clearance, an analogy with its human counterpart, is spleen-dependent. Allogeneic 51Cr-labeled red cells taken up by the spleen are retained for at least 6 weeks, and appear to represent a pool of intact cells that are destroyed no more quickly than syngeneic red cells. Sequential transfusions delivered at weekly intervals gradually abrogate rapid clearance, but a longer interval between injections allows the collapse curve pattern to persist. Increasing the dosage of donor red cells above the standard dose used in these experiments decreases the clearance rate, while reducing the dosage further accelerates clearance. Several attempts to implicate anti-RBC antibody, and to correlate the presence of such antibody with accelerated clearance, have failed. The grafting of an additional syngeneic spleen neither increases the proportion of allogeneic RBC removed from the circulation, nor reverses a temporary paralysis of the phenomenon induced by red cell overloading. These experiments imply that rapid clearance of allogeneic red cells is not mediated by a purely cellular mechanism, but that it requires a humoral substance that is readily exhausted, but fairly quickly replenished. The possibility that the rat equivalent of the H-2.7 mouse antigen might be responsible was considered, but appropriate experiments on mice have failed to support this idea. The findings in these experiments strengthen the analogy to the clinical event.