The interaction of Sepharose-immobilised IgG with isolated human placental syncytiotrophoblast plasma membrane vesicles.

Intact syncytiotrophoblast microvillous plasma membrane (StMPM) vesicle preparations isolated from human term placentae express surface Fc gamma receptor activity and will bind to Sepharose-immobilised human IgG. This IgG-StMPM Fc gamma receptor interaction has been shown to be stable during de-membranation using the anionic detergent 1% sodium deoxycholate (NaDOC) and to be preferentially contained in an NaDOC-resistant fraction of StMPM vesicles. Following NaDOC treatment of StMPM adsorbed on to Sepharose-IgG, subsequent desorption with the chaotrope 0.5 M NH4SCN disrupted the IgG-Fc gamma receptor interaction. The NH4SCN desorption product, however, contained several molecular components including IgG, transferrin and actin. These results indicate that StMPM surface Fc gamma receptors may interact with proteins of the microfilamentous core of StMPM vesicles and also possibly be topographically associated with some other cell surface components.