Concurrent redistribution of antigen receptors and surface immunoglobulin on antigen-binding cells.

Surface immunoglobulin can be demonstrated on almost all sheep erythrocyte rosette-forming cells in CBA and AKR mice, either by inhibition of antigen binding by anti-immunoglobulin or by immunofluorescence. When surface immunoglobulin on a rosette-forming cell is capped' by anti-immunoglobulin, the bound red cells migrate with the immunoglobulin, demonstrating that the receptor-combining site and immunoglobulin antigenic determinants share the same mobile unit in the membrane. These observations strongly support the concept that the antigen receptor is surface immunoglobulin (at least for B cells), and illustrate the usefulness of the capping' technique for studying the associations between membrane elements.