92-KD GELATINASE IS PRODUCED BY EOSINOPHILS AT THE SITE OF BLISTER FORMATION IN BULLOUS PEMPHIGOID AND CLEAVES THE EXTRACELLULAR DOMAIN OF RECOMBINANT 180-KD BULLOUS PEMPHIGOID AUTOANTIGEN

Eosinophils are prominent in bullous pemphigoid (BP), and proteases se creted from these and other inflammatory cells may induce disruption o f the basement membrane. We used in situ hybridization and immunohisto chemistry to localize the sites of 92-kD gelatinase expression in BP l esions. In all samples (20/20), a strong signal for gelatinase mRNA wa s detected only in eosinophils and was most pronounced where these cel ls accumulated at the floor of forming blisters. No other cells were p ositive for enzyme mRNA. Both eosinophils and neutrophils, however, co ntained immunoreactive 92-kD gelatinase indicating that active express ion occurred only in eosinophils. Degranulated eosinophils were also s een near blisters, and as demonstrated by gelatin zymography, immunobl otting, and ELISA, 92-kD gelatinase protein was prominent in BP bliste r fluid. No other gelatinolytic activity was specifically detected in BP fluid, and only small amounts of 92-kD gelatinase were present in s uction blister fluids. As demonstrated in vitro, 92-kD gelatinase clea ved the extracellular, collagenous domain of recombinant 180-kD BP aut oantigen (BP180, BPAG2, HD4, type XVII collagen), a transmembrane mole cule of the epidermal hemidesmosome. Our results suggest that producti on and release 92-kD gelatinase by eosinophils contributes significant ly to tissue damage in BP.