In vitro complement activation by antinuclear antibodies in the epidermis from patients with systemic sclerosis.

Skin biopsies from twenty-one systemic sclerosis patients with significant serum fluorescent antinuclear antibody (FANA) titres (more than 1:40) were examined by direct immunofluorescence (DIF) and by in vitro immunofluorescent complement (C) activation (C + DIF). Eight patients showed epidermal nuclear ANA deposits by DIF. In vitro complement activation was achieved in epidermal nuclei from all eight patients. In addition, one patient with diffuse scleroderma revealed a dense speckled, and two patients with the CREST syndrome a discrete speckled, epidermal nuclear staining pattern by C + DIF. The latter two patients showed high titres of anticentromere antibody in their sera. We consider that the C + DIF findings of these two patients with the CREST syndrome reflect binding of serum anticentromere antibodies to their antigens in vivo.