Detection of class-specific antibodies of pemphigus vulgaris using a solid phase radioimmunoassay

A sensitive solid phase radioimmunoassay was developed to detect class-specific pemphigus antibodies. COLO-16, a cell line derived from a human squamous cell carcinoma of the skin, was used as the substrate, since this cell line has been shown by indirect immunofluorescence to bind IgG antibodies in sera from patients with pemphigus vulgaris, but not from those with bullous pemphigoid. IgG antibodies to COLO-16 were significantly greater in sera from 17/24 patients (p less than 0.05) with pemphigus vulgaris than in sera obtained from a control population consisting of normal volunteers and patients with other dermatologic diseases. The relative binding of the positive sera correlated well (p less than 0.05, by Spearman's rank correlation test), with the endpoint determined by indirect immunofluorescence against monkey esophagus. This technique is 10-100 times more sensitive than immunofluorescence for the detection of pemphigus antibodies and will be useful in studying the cellular mechanisms controlling the synthesis of pemphigus antibody in vitro.