Preliminary characterization of an immunosuppressive inducer factor secreted by the JEG-3 choriocarcinoma cell line: In vitro and in vivo studies

PROBLEM: The direct immunosuppressive and suppressive inducing capacities of supernatants from human trophoblastic choriocarcinoma cell lines (HCS) are well investigated in several former studies. The responsible factor is not yet determined. METHOD OF STUDY: We first confirmed those data and we purified a 3-5-kDa suppressor-inducer factor from HCS by using high performance liquid chromatography (HPLC) on both DEAE and gel filtration columns, followed by ultrafiltration. We then tested the activities of such isolated fractions on in vitro immune responses from human cells and in vivo by its effects in a murine local graft-versus-host (GVH) assay (popliteal lymph node assay, PLN). RESULTS: A single fraction induces both ''direct suppression'' in vitro as well as in vitro suppressor cell activation/development in human peripheral blood lymphocyte cultures as assessed by suppression of cells cultured in such a fraction containing culture medium of the mixed lymphocyte reaction. Furthermore the very same fraction suppresses in vivo murine allogeneic immune responses as assessed by a local GVH reaction (PLN assay). CONCLUSIONS: We have isolated a suppressive fraction, whose activities suggest that it might be of interest not only in reproductive immunology, but also in transplantation systems.