Human embryo associated immunosuppressor factor(s) from pre- and post-implantation stages share some similarities

The present study demonstrates that embryo associated immunosuppressive factor(s) (EASF) secreted by the human embryo at pre- and post-implantation stages share some similarities. Human EASF was partially purified from embryo growth media of in vitro fertilized ova and from first trimester pregnancy sera. Non-pregnancy sera were fractionated in parallel. During each step of purification the fractions were tested for immunosuppressive properties using concanavalin A-stimulated lymphocyte proliferation assay. Analysis of EASF positive fractions on SDS-PAGE identified 14 kDa and 24 kDa molecules in embryo growth media and pregnancy sera. No such molecules were found in control sera, suggesting that these factors are embryo associated. The relationship of pre- and post-implantation EASF was also analyzed by EASF binding assay using murine anti-EASF antibody, which was raised against EASF isolated from embryo growth media. Results show that murine antibody bound to EASF purified from pregnancy sera, but not to identical fractions from control sera, indicating that these post-implantation EASF possess some similarity with pre-implantation EASF. Results also indicate that a species of suppressor factors present in embryo growth media and pregnancy sera were unique for their origin. Presence of these three EASFs at various stages of gestation may play a role in suppressing maternal cellular immune responses thereby preventing maternal rejection of the embryo.