Synthesis of Abnormal Immunoglobulins by Hybridomas from Autoimmune "Viable Motheaten" Mutant Mice

• Published in: The Journal of cell biology 1991-07, Vol.114 (1), p.35-43
• Main Authors: Schweitzer, Peter A., Taylor, Suzanne E., Shultz, Leonard D.
• Format: Article
• Language: English
• Subjects: Acetylglucosaminidase - metabolism; Animals; Autoimmune Diseases - immunology; Autoimmune Diseases - pathology; Autoimmunity (experimental aspects and models); B lymphocytes; Biological and medical sciences; Cell lines; Cells; Endoplasmic Reticulum - metabolism; Endoplasmic Reticulum - ultrastructure; Fundamental and applied biological sciences. Psychology; Fundamental immunology; Genetic mutation; Hybridomas; Immunoglobulin G - chemistry; Immunoglobulin G - metabolism; Immunoglobulin M - chemistry; Immunoglobulin M - metabolism; Immunoglobulin mu-Chains - chemistry; Immunoglobulins; Inclusion Bodies - immunology; Inclusion Bodies - ultrastructure; Mannosyl-Glycoprotein Endo-beta-N-Acetylglucosaminidase; Mice; Mice, Mutant Strains; Molecules; Plasma cells; Plasma Cells - immunology; Plasma Cells - ultrastructure; Secretion; Somatic cells
• ISSN: 0021-9525; 1540-8140
• DOI: 10.1083/jcb.114.1.35

Secretory defects in abnormal plasma cells, called Mott cells, that appear in lymphoid tissues of spontaneously autoimmune, "viable motheaten" (mev/mev) mice lead to deposition of immunoglobulin in RER-bound vesicles. Such vesicles have been termed Russell bodies. Cells with Russell bodies can also be observed rarely in normal animals, usually as a result of extreme antigenic loads or pathologic states. To understand why these abnormal cells appear commonly in mev/mevmice, we have established a panel of hybridomas that contain Russell bodies. Using immunochemical analysis and immunoelectron microscopy, we have characterized the secretory defects. Although these hybridoma cells synthesize a normal size heavy chain and it associates with light chain, the Russell bodies have many characteristics of inclusion bodies, which commonly appear in cells synthesizing mutant proteins and often are associated with incompletely or abnormally folded proteins. Pulse-chase experiments showed that immunoglobulins synthesized by these hybridomas accumulate rapidly into insoluble complexes and have an intracellular half life ∼10 time greater than normal immunoglobulins. The defect affected only the immunoglobulin derived from the mev/mevmice and did not affect the secretion of normal immunoglobulin produced by an IgG1-secreting fusion partner. In addition to accumulating intracellular immunoglobulins, many mutant cell lines also secreted immunoglobulin. Endoglycosidase H digestion was used to determine the state of processing of the N-linked carbohydrates on the immunoglobulin molecules. This analysis demonstrated that the N-linked carbohydrates on the secreted immunoglobulin were resistant to endoglycosidase H digestion, indicating that they were processed normally. The insoluble IgM molecules were sensitive to endoglycosidase H, which is consistent with their localization to the RER. We propose several models by which these abnormal immunoglobulin-secreting cells commonly appear in this autoimmune mutant mouse.