Fig. 4

Immunosuppressive mechanism of hChonJ. In order to investigate the mechanism involved in the suppression of T cell proliferation mediated by hChonJ cells, we evaluated whether this phenomenon was dependent on a cell to cell contact or soluble molecules. To study the involvement of the cell to cell contact mechanism, antibodies against PD-L1 and/or PD-L2 were directly added to the MLR culture. The involvement of soluble molecules was studied by using a trans-well system where hChonJ (upper compartment) was physically separated from the MLR culture (lower compartment). The proliferation of responder PBMCs was measured with 0.5 μCi ³H-thymidine. Alloreactive T cell proliferation that was suppressed by hChonJ cells was significantly restored by treatment of PD-L1 and/or PD-L2 antibodies (a), but hChonJ cells did not exert their suppressive effects on MLR culture in a trans-well system (b). Bars represented the change of ³H-thymidine uptake in comparison with an allogeneic MLR control (100%). These results are the representative of 3 independent experiments (Mean ± SE)