H5D12 monoclonal antibody identifies a 24-kD immunosuppressor factor produced by human chorio carcinoma cells

The purpose of this study was to identify and characterize embryo-associated immunosuppressor factor (EASF) secreted by chorio carcinoma cells with the help of EASF-specific monoclonal antibody H5D12 (raised against EASF purified from embryo growth media of in vitro fertilized human ova).

Paraffin-embedded slides of human chorio carcinoma as well as control cell lines were prepared, and immunohistochemistry was done by the avidin-biotin-peroxidase technique. EASF was affinity purified using H5D12-Sepharose 4B from culture media of cell lines and analyzed for immunosuppressive activity (by Concanavalin-A-induced lymphocyte proliferation assay) and molecular weight identity (by metabolic-labelling studies with 35S-methionine followed by immunoprecipitation and SDS-PAGE).

H5D12 showed intense immunostaining of BeWo chorio carcinoma cells. Biosynthetic labeling studies identifies this factor as a 24-kD molecule, and EASF bioassay indicates that this factor possesses immunosuppressive activity. No such immunosuppressive activity or similar molecules were identified when control cell lines were analyzed.

Monoclonal antibody H5D12 recognizes a 24-kD factor with immunosuppressive activity that is secreted by chorio carcinoma cells, which suggests that this is a unique factor and may be one of the key regulators of reproductive functions.