Figure 5.

ECP induced APC efficiently stimulate T-cell mediated anti-class I MHC cytotoxicity. Normal donor whole blood was processed through the clinical ECP apparatus to determine whether the procedure yields APCs capable of stimulating vigorous CD8-mediated cytotoxicity. This representative example, from 3 parallel experiments involving different normal donors, shows that APCs from an HLA-A2–positive donor initiated allogeneic normal HLA-A2–negative T cells to potently target HLA-A2-positive lymphoblasts. Cytotoxic T-cell responses were tested over a broad range of stimulator-to-responder ratios. Most prominently at ratios of 1:6 and 1:20, the ECP-generated APCs more effectively stimulated cytotoxic T-cell responses than did autologous pretreatment monocytes. These results indicate that the ECP-generated APCs are functionally capable of initiating CD8 T-cell targeting of class I MHC.