The lymphocyte surface. I. Relation between Fc receptors, C'3 receptors and surface immunoglobulin

Abstract Fc receptors, C'3 receptors and immunoglobulin (Ig) were detected on the surface of rat thoracic duct lymphocytes by a series of rosetting procedures. This paper describes the rosetting methods and some of the general properties of these cell surface components. It was found that the Fc receptors were blocked by antigen-antibody complexes and anti─Ag-B antibodies, they were lost in vitro at 37 °C, and they were not detected in the presence of 10-4 M azide. In contrast, the C'3 receptors were destroyed by treatment with trypsin, were insensitive to azide, and were not blocked by antigen-antibody complexes or anti─Ag-B anti-bodies. Both receptors were detected readily at 20 or 37 °C but not at 0 °C. Neither the Fc or C'3 receptors capped with surface Ig. From these differences in behaviour it was concluded that the Fc receptors, C'3 receptors and surface Ig probably represent separate molecules on the lymphocyte surface.