Electron microscopy of Fc receptors on human lymphocytes.

The membrane receptor for Fc portions of IgG (FcR) was localized on the cell surface of humans lymphocytes by electron microscopy. The electron microscopic markers for FcR were soluble ferritin 7S anti-ferritin immune complexes prepared in forty times antigen excess than needed at equivalence. Fc receptors on the lymphocytes labelled at 0 degree in the presence of sodium azide were seen as discontinuous patches on the cell surface. In control experiments, no labelling was observed, which included lymphocytes treated with ferritin only or with F(ab')2 immune complexes as well as glutaraldehyde-fixed lymphocytes treated with 7S anti-ferritin immune complexes. The findings are discussed with relation to the widely accepted membrane fluidity model.