Cell surface immunoglobulin. I. Isolation and characterization of immunoglobulin from murine myeloma cells.

Abstract

Enzymatic radioiodination has been used to investigate the cell surface of three murine myeloma tumors that secrete Ig. In each cell type studied (IgG 1 , IgG 2a and IgA), radiolabeled Ig can be obtained from the cell surface by specific precipitation. In one cell line, surface IgG was also identified by digestion with trypsin followed by fingerprinting as well as by digestion with papain into characteristic Fab and Fc fragments. The Fc fragment contained a significant amount of radioactivity consistent with the concept that the IgG molecule is fully exteriorized. In each plasma cell line studied, Ig was associated with a molecular weight equal to or greater than 200,000 daltons which may be the complex between Ig and the molecule(s) on the plasma membrane to which it is attached.