The uptake of IgG by human placental chorionic villi: a correlated autoradiographic and wide aperture counting study.

The uptake of 3H-IgG into human placental chorionic villi in vitro takes place for at least 1 h at 37 degrees C and at 4 degrees C. The rate of uptake is lower at the latter temperature, but still about 20 per cent of the 37 degrees C total. Measurement of cell-associated redioactivity at 4 degrees C cannot therefore be used as a measure of binding: genuine uptake, probably as a result of endocytosis, appears to occur at this temperature. Some proportion of the uptake of IgG at 37 degrees C can be inhibited by colchicine and by cytochalasin B, but some is refractory to these treatments. A coated vesicle-enriched fraction isolated from placenta previously incubated with 3H-IgG was found to be associated with radioisotope.