Nature of IgG anti-lymphocyte autoantibody-reactive molecules shed from activated T cells in systemic lupus erythematosus.

Shedding of cell-surface antigens that react with anti-lymphocyte autoantibodies in systemic lupus erythematosus (SLE) is well-recognized, but the nature of such molecules is unknown. The present investigation demonstrates the rapid shedding of three IgG antibody target molecules of Mr 55,000, 37,000, and approximately 32,000 from the surface of mitogen-activated peripheral T cells during brief incubation at 37 degrees C. Sera lacking IgG anti-lymphocyte antibodies stained none of the three antigens. Absorption of antibody-positive sera with viable HSB-2 cells, a primitive T-cell line lacking HLA antigens and many CD antigens characteristic of mature peripheral T cells, eliminated staining of the shed molecules. These data delineate the number and estimated molecular mass of anti-lymphocyte autoantibody target molecules that are shed from the surface of T cells, and provide further insight into potential mechanisms by which anti-lymphocyte antibodies contribute to the pathogenesis of SLE and related disorders.