First-set Allograft Rejection Research Articles

The histology at various stages of acute rejection in concordant xenogeneic heart transplantation. A sequential study in rodents.

In an attempt to describe early morphologic changes in heterotopic xenogeneic heart transplantation a sequential study was performed in a hamster-to-rat model. Mild morphologic changes observed after four to six h were characterized by slight interstitial edema and focal myocyte damage with fragmentation and loss of myofibrillar elements. No lymphocytic infiltration appeared. Moderate morphologic changes observed after 12-24 h were characterized by moderate interstitial edema, and the appearance of mild hemorrhage and scattered extravasated neutrophilic granulocytes. The myocardium had more widespread areas with myocyte damage, sometimes with small foci of necrotic cells and adjacent neutrophilic granulocytes and macrophages. Vascular changes with perivascular edema and swelling of the endothelium were seen and a few neutrophilic granulocytes could be found in the vessel walls. No lymphocytic infiltration appeared. Severe morphologic changes observed after 44-48 h or at the time of complete rejection were characterized by severe interstitial hemorrhage, appearance of widespread necrosis and marked vascular changes with development of leukocytoclastic-like vasculitis, possibly with thrombosis. Only a few lymphocytes appeared. The findings were essentially different from those observed in allogeneic heart transplantations, where classical first-set allograft rejection was seen. In normal donor hearts and syngeneic transplanted hearts used as controls, no significant morphologic changes were demonstrated. On the basis of this study we consider xenogeneic acute rejection to be primarily of the humoral type.

Development of Transplantation Immunity and Restoration Experiments in the Thymectomized Amphibian

This paper examines the thymic dependence of alloimmunity in amphibians. In Xenopus , the presence of a thymus during the first 2 weeks of life is essential for the development of normal first-set skin allograft immunity. Thymectomy during this early period always impairs the alloimmune response of young adult toads. However, most of these thymectomized animals are able to completely destroy skin allografts, albeit with prolonged rejection times. Chronic graft rejection, rather than tolerance, still occurs following thymectomy as early as 5 days, when the thymus contains no small lymphocytes. In contrast to the considerable differences in first-set allograft survival times in control and early-thymectomized Xenopus , second-set grafts, applied subsequent to first-set destruction, are rejected in acute fashion (<3 weeks) in both groups. That the defect in first-set alloimmunity is specifically related to absence of thymus has been confirmed by implanting allogeneic thymus 2 weeks post-thymectomy. The donor thymus remains healthy and restores the allograft response to normal. In contrast, allogeneic spleen does not reconstitute and itself often undergoes destruction. Preliminary autoradiographic experiments on lymphoid tissue involvement in first-set allograft rejection are also described.

Chronic allograft rejection in the iguana Ctenosaura pectinata

SummaryAdult male and female iguanas, Ctenosaura pectinata, were auto- and allografted. Skin allografts and autografts behaved like those of other vertebrates; they healed in initially but allografts later showed signs of rejection recognized mainly by pigment cell destruction. At 25°C chronic rejection of first-set allografts in the iguana, as indicated by the survival times, is more like the rejection pattern of urodeles and apodans than that of anuran amphibians or fishes. The data support a view that allograft rejection is by an immune process since accelerated rejection of some second-set grafts occurred while the rest showed enhanced survival. In addition, an inflammatory response, characterized by lymphocytic infiltration, was always associated with destroyed grafts.

Chronic Skin Allograft Rejection in the Apodan Typhlonectes compressicauda

Allografts were exchanged between adults of the aquatic apodan Typhlonectes compressicauda. Skin allografts and autografts behave like those of other amphibians studied; they heal in initially but later show signs of inflammation and destruction initiated as pigment cell destruction, vasodilation, and hemostasis. As in other vertebrates, rejection is accompanied by destruction of the various tissue layers and infiltration of the graft by lymphocytes and granulocytes. Chronic rejection of first set allografts, as indicated by the survival times in this caecilian, is more similar to the rejection pattern of urodeles than of anurans. The data support a view that allograft rejection in the caecilian is by an immune process since accelerated rejection occurred in some second-set grafts while others showed enhanced survival.