DIRECT RECOGNITION OF MINIATURES SWINE ENDOTHELIAL CELLS BY HUMAN CD8 T CELLS INVOLVES BOTH XENOGENEIC SLA CLASS I MOLECULE AND ASSOCIATED PEPTIDES

Abstract

78 The theoretical basis of xenorecognition is poorly defined. It is not known how the disparity in MHC molecules between species such as human and porcine affects the TCR MHC interaction. Human anti-miniature swine xeno responses is of particular interest because of the potential clinical use of miniature swine as an organ donor in human transplantation. We generated human anti-miniature swine cytolytic T cell line which showed swine haplotype restricted lysis of porcine endothelial cells (PAEC) from z/z haplotype. In this communication we demonstrate that; 1) human CD8 T cells directly recognize and differentiate swine leukocyte antigens (SLA) expressed on porcine endothelial cells (PAEC), 2) human CD8 is directly involved in the interaction with SLA class I molecules, and 3) xenogeneic peptides associated with the SLA molecules are also required for this interaction. To demonstrate to role of xenogeneic peptides in this xenorecognition, first we stripped peptides from SLA molecules by brief citric acid (pH 3.0) treatment. Untreated z/z PAEC was lysed 25% at E:T 8:1; z/z PAEC stripped of peptide was lysed 11%. Peptides eluted from affinity purified z/z SLA class I molecules but not from the irrelevant y/y SLA class I molecules, restored the lysis of the target cells. Second, peptides eluted from z/z SLA class I molecule but not from the irrelevant y/y SLA class I molecule induced the lysis of human class I null 721.221 and 721.220 cell lines transfected with a SLA class I heavy chain from the z/z haplotype. The above experiments indicates that both the xenopeptides and SLA class I alleles confer specificity for the human CD8 mediated lysis of porcine cells. T cell clones derived from the T cell line also showed similar results. In conclusion, our results demonstrated that despite the difference in MHC molecules between species, recognition of porcine MHC by human T cells is similar to direct allo-recognition, i.e. human TCR recognizes xenogeneic MHC-peptide complex.