Plasmin-like proteinase associated with high molecular weight complexes in blister fluid of bullous pemphigoid

Blister fluid from tense bullae of 10 patients with bullous pemphigoid was investigated using a radial caseinolysis assay and zymography. Proteolytic activity, varying from 4.7 to 10 micrograms/ml, was found in 3 out of 10 patients, by using the caseinolysis assay. Zymography revealed that a major part of this caseinolytic activity co-migrated with plasmin standard. In addition, in the zymography, proteolytically active high molecular weight complexes were seen. This characteristic pattern was seen in the zymography of both positive and negative samples in the caseinolysis assay. These high molecular weight complexes were not seen in the zymography of the blister fluid of 2 patients with epidermolysis bullosa or in the suction blister fluid of 3 healthy control patients. These findings suggest that plasmin is generated at some phase of the blister formation, being possibly involved in the pathomechanism of bullous pemphigoid.