Analysis of autoantibodies to cell cycle-associated antigens

Abstract To determine the specificities of autoantibodies targeting cell cycle-associated antigens in rheumatic diseases, we studied 30 sera which were obtained from patients visiting our hospital and which exhibited a variegated speckled pattern in indirect immunofluorescence (IF). The immunoreactivities of the sera were analyzed by Western blotting (WB) and IF. Various reactivities to cellular components were observed in IF. The sera reacted with proteins of various molecular weights in WB. Serum OH from a patient with rheumatoid arthritis showed fine speckled nucleoplasmic and nucleolar staining at interphase, discrete dot staining associated with chromosomes and the midbody at mitosis, and reacted with a 34-kD polypeptide in WB. The target antigen was different from proliferating cell nuclear antigen (PCNA). The 34-kD antigen was characterized by IF using double staining procedures and cell synchronization. The results showed that the expression of the antigen was mainly observed between the late G1 and M-phases. This study indicated that various cell-cycle-associated antigens were recognized in sera from patients with rheumatic diseases, and suggested that a 34-kD antigen recognized by serum OH was a novel cell cycle-associated autoantigen.