Indirect recognition of donor MHC class II antigens in human transplantation

Abstract

To investigate the role of the indirect pathway of recognition in human allograft rejection, we have mapped the dominant T cell determinant of the HLA-DRβ1(*)0101 molecule presented by the DRβ1(*)1101 antigen. A synthetic peptide (pp 22-35) corresponding to the sequence of the dominant peptide determinant was used for testing the frequency of in vivo activated T cells in the graft and in the periphery. DRβ1(*)1101-positive patients carrying a heart allograft mismatched for the HLA-DR1 antigen showed no reactivity to pp 22-35 during quiescence. However, interleukin-2-responsive T cells, which were pp 22-35 specific, were found in the circulation prior to and at the time of acute and chronic rejection. The response of in vivo and in vitro activated T cells was inhibited at high concentrations of peptide 22-35. This data suggests that indirect recognition plays an important role in allograft rejection and that it can be abolished by high zone tolerance induction.