Regional variation in the expression of bullous pemphigoid antigen and location of lesions in bullous pemphigoid.

The expression of bullous pemphigoid (BP) antigen in different locations on the body was estimated from the highest dilution of BP sera giving a positive reaction at a site by indirect immunofluorescence. Three sera with high titers (640-1280) of BP antibodies against monkey and guinea pig esophagus were reacted with 46 specimens of normal human skin. There was marked variation in the expression of BP antigen in skin obtained from different sites. The greatest expression of BP antigen was in skin obtained from the flexor surfaces of the arm, leg, and thigh. All specimens from these sites reacted with high dilutions (1:640-1:2560) of BP antibodies. BP antigen was expressed least in skin specimens from scalp, face, and extensor surface of the arm. No BP antigen could be demonstrated in 17% of specimens from these locations and the remainder reacted only with low dilutions (1:40-1:160) of BP antibodies. Skin from trunk, knee, and extensor thigh had intermediate amounts of BP antigen. Similar results were seen with all 3 BP sera. Similar reactions were observed in multiple skin specimens obtained from different sites in the same individual. Of note is that the greatest expression of BP antigen was in areas commonly involved in this disease (flexural surfaces), whereas the least was seen in areas (scalp, face, extensor arm) which are rarely involved. The apparent correlation between the expression of BP antigen and the location of lesions in bullous pemphigoid, suggests that BP antigen expression may play a role in the distribution of skin lesions in this disease.