Ovine and Human Placental IgG inhibit Human Natural Killer Cell Cytotoxicity in Vitro.

Abstract

To determine the effect of ovine and human placental lgG on human natural Killer (NK) cell cytot oxicity in vitro placental lgG was eluted at acidic pH and purified by ion exchange and subsequently by affinity chromatography on protein G and protein a sepharose columns. These antibodi es were analysed for presence of IgG by immune-electrophoresis and relative purity determined by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS PAGE). The effect of these antibodies on human NK cell cytotoxicity was investigated by 51Chromium Release Assay using human K562 cells as targets and human peripheral blood lymphocytes as effector cells. Both ovine and human placental IgG inhibited human NK cell cytotoxicity in a dose dependent manner. Placental IgG may down-regulate the cytotoxic effects of NK cells in 1•ivo by competitivel y excluding the bindin g of NK cells to their respective Targets on the trophoblast. Alternatively, these antibodies may themselves be toxic to NK cells. Either way, the presence of these anti bodies on the placental trophoblastic may prevent the binding of NK cells and subsequent immunological rejection of the fetal allograft. Also, ovine placental lgG may be functionally similar to its human counterpart and ma y therefor e be suitable as a model for the study of maternal fetal interaction during pregnancy in humans.