Complement-fixing intercellular antibodies in a case of cicatricial pemphigoid

A patient with ocular and oral lesions, as well as cicatricial pemphigoid, had intercellular antibodies to a titer of 80 by indirect immunofluorescence (IF) microscopy staining tests with her serum. These were identified as pemphigus-like antibodies, since direct IF microscopy indicated no intercellular IgG deposits. Complement IF microscopy tests of the serum gave a closely comparable titer (40) of intercellular antibodies. Since serum samples of patients with true pemphigus either fail to fix complement or have much lower complement fixation titers, the complement IF microscopy tests of patients' serum samples may be of value in differentiating pemphigus-like antibodies from pemphigus antibodies.