Immunoglobulin Synthesis and Secretion

Cells from an established line of Burkitt's lymphoma (Daudi) and a mouse myeloma (P(3)K) were pulse-labeled in vitro with (3)H-leucine, and immunoglobulin was immunologically precipitated from cell lysates and secretions. In contrast to P(3)K cells, Daudi cells synthesize a small amount of Ig which is not secreted. Subcellular fractionation experiments indicated that Ig of Daudi cells is synthesized on membrane-bound polyribosomes and enters the cisternae of the microsomes. Ig in the microsomes could be labeled with either (3)H-galactose or (3)H-fucose suggesting that transport proceeds to the Golgi complex. Additional evidence indicates that Ig molecules are transported to the plasma membrane but are not cleaved from the cell surface. These results together with other studies of Burkitt lymphoma cells suggest that the Daudi line may represent a clone of neoplastic cells derived from normal lymphocytes which synthesize but do not secrete Ig. Similarities between lymphoma cells and antigen-binding cells are discussed.