Direct immunofluorescent (IF) staining was carried out on skin biopsy specimens of patients with skin diseases (including bullous skin diseases), with use of specific antisera to human IgG, IgA, IgM, and β1C/β1A globulin. IgG and complement (C') were consistently found in the basementmembrane-zone area in skin lesions of patients with bullous pemphigoid. Positive direct IF staining in bullous pemphigoid may assume considerable diagnostic importance, especially in cases without demonstrable circulating antibody. IgG was consistently observed in the intercellular-substance areas in lesions of patients with pemphigus, whereas C' was not detected. IgA and IgM, encountered in a few instances only, appear to have little, if any, significance in either disease. Special studies, involving autoreactivity, were done.
Jordan RE, Triftshauser CT, Schroeter AL. Direct Immunofluorescent Studies of Pemphigus and Bullous Pemphigoid. Arch Dermatol. 1971;103(5):486-491. doi:10.1001/archderm.1971.04000170020004