2 MAJOR AUTOANTIGEN-ANTIBODY SYSTEMS OF THE MITOTIC SPINDLE APPARATUS

Objective. To characterize human autoantigen-antibody systems related to the mitotic poles and spindles. Methods. Thirty-seven human sera wi th autoantibodies staining mitotic poles and spindles in indirect immu nofluorescence (IIF) studies were further characterized by immunofluor escence on mitotic cells and by immunoblotting and immunoprecipitation . Clinical diagnoses meeting the American College of Rheumatology crit eria were based on chart review and interview with the corresponding p hysicians. Results. Two autoantibody systems reactive with mitotic pol es and spindles were defined. Type 1 nuclear mitotic apparatus (Nu-MA- 1) antibodies were identified in the serum of 30 patients. Interphase cells showed a fine, speckled, nuclear staining, while mitotic cells h ad bright staining of the rim of the centrosomes and light staining of the spindles proximal to the centrosomes. In telophase, the staining shifted from the centrosomes to the reforming nuclei. On immunoblottin g, anti-NuMA-1 sera reacted with a 210-kd protein. The reactivity of t hese sera was identified (with the aid of reference antibodies) as the previously described NuMA antigen-antibody system. Clinical informati on was available for only 17 of the 30 patients with anti-NuMA-1; of t hese, 17 (53%) had clinical and lip biopsy finding that met the criter ia for Sjogren's syndrome. NuMA-2 antibodies were found in the sera of 7 patients. Interphase cells showed no nuclear or cytoplasmic stainin g, but mitotic cells had brightly stained poles and spindles. At anaph ase/telophase, staining shifted to the midbody and the intercellular b ridge. Anti-NuMA-2 sera immunoprecipitated a protein of 116 kd. This g roup of patients was more heterogeneous and had both systemic and orga n-specific autoimmune diseases. Conclusion. NuMA protein (here called NuMA-1) and a 116-kd protein (here called NuMA-2) are the major target s of the autoimmune response in the mitotic apparatus, since most of t he selected sera (based on IIF staining of the mitotic spindles and po les) recognized 1 of these 2 antigens.