CELLULAR XENORESPONSES - ALTHOUGH VIGOROUS, DIRECT HUMAN T-CELL ANTI-PIG PRIMARY XENORESPONSES ARE SIGNIFICANTLY WEAKER THAN EQUIVALENT ALLORESPONSES

The in vitro human T cell xenoresponse to porcine stimulators has been examined in detail. Alveolar lavage cells (AL cells), derived from wa shouts of porcine lungs were found to possess phenotypic and functiona l properties of porcine dendritic cells, Using AL cells that had been allowed to mature during overnight incubation, we have shown that the ''direct'' T cell xenoresponse is mediated predominantly by CD4(+) T c ells that recognize SLA-DR molecules, Limiting dilution analysis assay s indicate a high precursor frequency of such cells in the peripheral blood of human responders, However, in a formal comparison with direct alloresponses, the proliferative response of human T cells to porcine dendritic cells was found to be significantly weaker, Using HLA-DR an d SLA-DR-transfected murine and porcine cell lines, we have shown that this relative weakness is due in part to an inefficiency of cognate i nteractions. In contrast, the noncognate interactions between human T cells and porcine stimulators are as efficient as those with human APC .