Immune diagnosis of pure ocular mucous membrane pemphigoid: indirect immunofluorescence versus immunoblot

Diagnosis of pure ocular mucous membrane pemphigoid (OMMP) is based on the demonstration of linear depositions of IgG, IgA, C3 or combinations thereof alongside the epithelial basal membrane zone with direct immunofluorescence (DIF) or immunoperoxidase ( DIP) analysis of a freeze biopsy of the conjunctiva in patients with cicatrizing kerato-conjunctivitis. The aims of this study were: 1) to investigate whether the direct immunoperoxidase method is more sensitive than direct immunofluorescence; 2) to analyse whether circulating antibodies against basement membrane autoantigens can be detected in DIF positive and DIF negative patients and which method is the most sensitive for this. In 11 patients with exclusively cicatrizing keratoconjunctivitis, biopsies were evaluated with DIF and DIP. Serum was investigated with indirect immunofluorescence and immunoblot. Immunofluorescence analysis revealed linear IgG and/or IgA depositions in five out of 11 conjunctival biopsies. These depositions were less intense with immunoperoxidase analysis. Serum immunofluorescence analysis was positive in only one case (20%); immunoblot analysis for circulating antibodies was positive in 4 of 5 patients (80%) with pure OMMP. With the methods used in this study: a) the immunoperoxidase analysis was no more sensitive than direct immunofluorescence, and b) the immunoblot was more sensitive in demonstrating circulating antibodies than indirect immunofluorescence.