Autoantibodies to human nuclear antigen(s)-HNA-in connective tissue diseases and other disorders

Autoantibodies reacting with nuclear antigen(s) on human cells (HNA) with weak or without reactivity on nuclei of other species have been found by the indirect immunofluorescence technique used in routine tests for the diagnosis of autoimmune diseases. Precipitin lines were obtained by counterimmunoelectrophoresis (CIE) only when human lymphocyte extracts were used and not with rabbit thymus acetone powder. By comparison with reference sera, the autoantibodies directed to HNA were found to be different from SSA/Ro antibodies and did not give the fluorescence pattern of anti nuclear mitotic apparatus (NuMA) antibodies on HEp-2 cells. The prevalence of sera with anti-HNA antibodies not associated with other antinuclear antibodies (ANA) is low (about 0.7% of ANA found in routine assay). In association with ANA of other specificities, the prevalence of anti-HNA antibodies, demonstrated after absorption of sera with rat liver acetone powder, was higher (about 1% of ANA positive sera). By treatment with physicochemical agents and enzymes, the HNA was found to be a DNA (glyco)-protein complex extractable with saline solution, resistant to 56 degrees C for 6 h and stable at pH values ranging from 3 to 10. Anti-HNA antibodies were found in patients with mild connective tissue diseases, but also in idiopathic interstitial pneumonia and in chronic hepatitis.