CELL-MEDIATED IMMUNE REACTIVITY IN THE XENOGENEIC TRANSPLANTATION COMBINATION HUMAN-ANTI-PIG

The worldwide lack of human organ donors puts the pig as potential xen ogeneic donor species into the prime of interest. Aim of the present i n vitro study is the analysis of T-cell activation in the clinically a ttractive combination ''pig-to-human''. Peripheral human blood leukocy tes (hPBL) and peripheral porcine blood leukocytes (pPBL) were co-cult ered for 4-8 days in the xenogeneic mixed lymphocyte reaction (xMLR) a nd cell proliferation was measured by H-3-thymidine uptake. Both cell populations were separated into T-cells and antigen presenting cells ( APC) to analyze direct and indirect antigen recognition. The results s how that (a) activation of human T-cells occurs, (b) the strength of a ctivation depends e.g. on the human responder (''high'' and ''low'' re sponders), (c) the strength of activation is independent of the respon der's HLA-DR status, and (d) direct T-cell activation dominates over i ndirect activation. Thus, T-cell activation is another immunological b arrier that has to be overcome before xenotransplantation can be clini cally approached.