No abstract

An anti‐dog thymocyte serum was prepared in six horses by four weekly injections of dog thymocytes, and was tested for immunosuppressive capacity during the course of immunisation by its ability to inhibit the formation of rosettes between dog spleen cells and sheep red blood cells. Antithymocyte globulin prepared from the individual sera was administered to dogs receiving renal allografts with simultaneous bilateral nephrectomy, and the prolongation of survival was correlated with the rosette inhibition litres (RIT) of the sera. A rise in serum RIT occurred after the third immunizing dose in all four horses producing immunosuppressive serum, with little or no response in the two horses producing non‐immunosuppressive serum. These observations have led to considerable saving in time and expense in the production of antithymocyte globulin for experimental and clinical purposes in our own laboratories, and we recommend that continued immunisation and final bleeding out should be performed only if such a rise in RIT has been demonstrated.