Indirect immunofluorescence to demonstrate lichen planus specific antigen (LPSA) in lichen planus

Background: Current evidence suggests that lichen planus is an immunological disease. Cytotoxic CD8+ cells in the lesional epidermis recognize a unique antigen called lichen planus specific antigen. This antigen could be demonstrated by indirect immunofluorescence using the patient′s serum and autologous lesional skin. Aim: To study indirect immunofluorescence pattern in lichen planus, among Indian patients. Methods: Twenty-five consecutive patients with the clinical diagnosis of lichen planus were enrolled in the study. Direct immunofluorescence was done in all patients. Indirect immunofluorescence using lesional skin as substrate was done in all 25 patients and five patients with other dermatoses. Results: A specific fluorescence pattern corresponding to the distribution of lichen planus specific antigen was observed in the stratum spinosum and granulosum in 22 (88%) patients. It was absent from other parts of the epidermis, dermis and in patients with other dermatoses. Conclusion: Indirect immunofluorescence is a useful adjuvant test in lichen planus, particularly in atypical cases.