Binding of human EPF to receptors on PMBC as a first signal of pregnancy immunomodulation.

The interaction between human early pregnancy factor (EPF) and a specific receptor present on human peripheral blood mononuclear cells (PMBC) has been assessed. EPF was radioiodiated by the lactoperoxidase method to a high specific activity, and the [125I]EPF obtained bound in a specific and saturable manner to the receptors on PBMC. Saturation of the binding sites occurred at 10(-9) M. There were 6600 specific binding sites per cell in cells partially purified from pregnant women and fewer in those from non-pregnant women. Unlabelled EPF was capable of competing for binding sites with [125I]EPF, while the binding of [125I]EPF was not inhibited by human chorionic gonadotrophin. A new assay was used that permits the culture of PBMC and the detection of the surface IgG expression in the same microplate. With this method the influence in vitro of human EPF on lymphocyte expression was tested. The results demonstrated a specific inhibition of surface IgG expression of PBMC using a very low concentration of EPF (10 pg/ml). [ABSTRACT FROM AUTHOR]