Evidence that soluble class I antigen in donor serum induces the suppression of heart allograft rejection in rats.

The effect on heart allograft rejection in the rat of continuous slow infusion of donor MHC type serum is described. DA (RT1a) serum delayed significantly the rejection of PVG.RT1a heart grafts in PVG recipients (p less than 0.01), but did not affect survival of third-party WAG grafts. Grafts at both early and late stages of rejection were prolonged by serum infusion. Removal of soluble class I MHC antigen from DA serum by affinity chromatography on a monoclonal anti-class I antibody column completely abolished the immunosuppressive effect. The results may indicate that soluble class I antigen can act as a specific immunosuppressive agent in allograft rejection.