MODIFICATION AND FATE OF J-CHAIN IN MYELOMA CELLS IN PRESENCE AND ABSENCE OF POLYMERIC IMMUNOGLOBULIN SECRETION

Processing of J chain in various mouse myeloma cell lines was examined by incorporation of radioactive cystine, followed by analysis of proteins by immune precipitation and gel electrophoresis. J chain was synthesized by all myeloma‐derived cell lines examined, but not by nonmyeloma cell lines, even of B lymphocyte lineage. Secretion of J chain occurred only from cells secreting IgA or IgM. The J chain synthesized in other myeloma cell lines, was altered to a form that did not migrate at the rate of J chain during electrophoresis and was not recognized by the anti‐J chain antiserum. This alteration, probably due to degradation, occurred at a similar rate to the secretion of J chain by cell lines producing IgA or IgM. Some degradation of J chain may also occur in cell lines secreting J chain. Although the J chains from several cell lines were indistinguishable by gel electrophoresis when first synthesized, secreted J chains from three cell lines all showed slight differences in mobility both from one another and from intracellular J chain. The change in mobility occurred at or near the time of secretion of immunoglobulin, and was consistent with the addition of different amounts of carbohydrate to J chain in the three different myelomas. Copyright © 1978 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim