THE PRESENCE OF HUMORAL FACTORS IN HOMOGRAFT REJECTION OF THE TRANSPLANTED HEART

Abstract

The mechanism of rejection of the transplanted dog heart was studied in experiments in vivo and in vitro. Vascular permeability was measured by determining the degree of tissue radioactivity after intravascular injection of radioiodinated albumin (RISA). One hour after transplantation, vascular permeability was increased. This was more pronounced when the rejection was accelerated. In experiments, in vitro perfusion of the isolated heart with homologous plasma demonstrated slightly increased capillary permeability one hour after the onset of perfusion; perfusion with sensitized plasma caused a significant rise in vascular permeability. Cellular reaction was absent in the homografted heart one hour after transplantation. In only 3 of 25 perfusions in vitro was cellular reaction present characteristic of homograft rejection. This occurred in hearts perfused with sensitized plasma. The results illustrate that homograft rejection can commence with signs of increased vascular permeability one hour after transplantation. They further show that humoral factors may play a predominant role in homograft rejection.