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15 AU81, a synthetic prostacyclin analog, inhibits human mixed lymphocyte culture responses in a dose-dependent manner at concentrations within a range [0.1 to 10.0 micrograms/ml] similar to that of cyclosporine, methylprednisolone, antilymphocyte serum, and prostaglandin E1 and E2 analogs. Using the median-effect analysis to dissect immunosuppressive interactions, 15 AU81 and cyclosporine were shown to produce synergistic effects on human peripheral blood lymphocyte activation upon phytohemagglutinin or anti-CD3 monoclonal antibody stimulation. In vivo, 15 AU81 potentiated the effect of cyclosporine to prolong the survival of rabbit renal allografts using concentrations of each agent that were individually ineffective. Furthermore, addition of 15 AU81 mitigated functional damage of rabbit kidneys due to high-dose cyclosporine therapy. These observations suggest that the addition of 15 AU81 may broaden the therapeutic window of cyclosporine by potentiating immunosuppression and mitigating nephrotoxic effects.

There are many conflicting reports on the survival of cultured keratinocyte allografts (CKAs). Studies were performed in the rabbit model to elucidate further the fate of CKAs. Of 24 CKAs, 7 were identified as technical failures, 13 displayed classical macroscopic evidence of rejection with a prolonged mean survival time of 2.8 days, compared to non-cultured allograft controls (p < 0.01), and 4 failed to display typical macroscopic evidence of rejection. Furthermore, the time to eventual wound healing of the classically rejected CKAs were delayed by 6.0 days (p < 0.0001), compared to identical non-grafted control wounds.

A technique is described for the culture of disaggregated rabbit keratinocytes and the production of confluent sheets of immunologically pure keratinocytes suitable for use in transplantation studies. The benefits of various feeder layers, nutrients and growth hormones were examined by the use of paired controls. The ability of the cultured keratinocyte sheets to be removed from the culture vessel intact and survive as viable autografts was demonstrated, thus establishing a new animal model for the investigation of allograft rejection responses to cultured keratinocytes. The benefits of using the rabbit model for such studies and the advantages of this culture technique over a previously described method of rabbit keratinocyte cell culture are discussed.

Serial antibody dependent cellular cytotoxicity (ADCC) effector cell function estimates and renal biopsies were obtained from 74 recipients to determine the ADCC modifications induced by azathioprine/steroid therapy and the histological character of rejection associated with the modifications. Recipients with suppressed ADCC did not experience rejection episodes while recipients with non-suppressed ADCC suffered graft failure following steroid-resistant rejection. The majority of recipients experienced reversible rejection episodes which were preceded by increased ADCC activity in the five day period preceding the commencement of high-dose steroid anti-rejection therapy. It was concluded that ADCC was active in the rejection process, and that in vitro ADCC measurement provided a means of monitoring the modifications induced by azathioprine/steroid therapy which promote a post-graft term free of rejection episodes.

Isograft studies were performed in the murine model of cardiac transplantation to investigate the morphologic effects of operative ischemia. Primarily vascularized CBA mouse hearts were grafted heterotopically into the recipient CBA mouse's abdomen with standard microsurgical techniques. After ischemia times of 30 and 60 minutes, histologic examination showed minimal myocardial damage, with necrosis or scarring occupying less than 5% of the cross-sectional area of hearts bisected from apex to base after grafts had been removed on the seventh day after transplantation. Maximal ischemic damage was seen at 7 days after transplantation after 120 minutes of ischemia, with more than 30% myocardial necrosis or scarring of myocardial tissue. Isografts performed with ischemia times of less than 60 minutes were followed for more than 100 days. All hearts showed a fine, generalized, perimyocytic fibrosis, which was maximal at 28 days after transplantation and did not progress thereafter. These results will serve as important control measures for future studies in this model because ischemic damage must be considered in examining histologic samples from long-surviving cardiac allografts maintained in immunosuppressed recipients.