Histologic and electron microscopic characterization of the antiperinuclear factor antigen.

The presence of the antiperinuclear factor, an autoantibody that recognizes cytoplasmic antigens, was detected in sera from patients with rheumatoid arthritis (59%), seronegative rheumatoid arthritis (36%), systemic lupus erythematosus (46%), systemic sclerosis (26%), and in nonautoimmune controls (10%). The antigenic perinuclear granules were found in the stratum intermedium layer of the buccal mucosa. Granules exhibited histologic features of nucleoproteins, stained for ribonucleoprotein, and showed the ultrastructural characteristics of aggregated rough endoplasmic reticulum. The antiperinuclear factor may recognize a common autoantigen in connective tissue disease.