Investigations on the Binding Sites of the Basement Membrane Zone for Pemphigoid Antibodies in Vitro. I. Enzymatic Action on the Active Groups of Human Skin

Abstract

At the present time, nothing is known of the antigenie structurcs or the antibody binding sites for base ment membrane zone antibodies of pemphigoid patients located in the basement membrane zone of the human skin. In the course of experiments to delineate this area, we have studied the action of various enzymes in vitro. These investigations showed that the exposure of cryostat sections of human skin to the action of proteolytic en zymes (papain/trypsin) produced an increase in antibody binding capacity of the basement membrane zone for basemenl membrane zone antibodies. This was demon strated by an increased inlensity of fluorescence of the basement membrane zone in 17/25 of the skin samples testcd from different patients and by an increa�e of 1-7 titre dilution steps as compared with control sections not previously incubated. From various enzymes testcd the a-and /:l-galactosidases in 19/21 skin samples also showed increased intensity of fluorescence. and titres increased by I--<i dilution steps. The quantitative evalua tion of our experimental results showed rhat incuhation with galactosidases and proteolytic enzymes produccd an activation independent of the titre, while there was. in addition, an inactivation dependent on the leve) of the initial titre produced by the action of papain and trypsin only. Furthermore. we belicve these latest results, together with immunochemical studies on the bascment membranes from the literature, allow conjecture on the possible site of enzyme action. This site must be in the immediate vicinity of the hydroxylysine on the molccule. In agreement with other authors and results. we have developed the hypothesis that the action of proteolytic enzymes causes the basement membrane zone to become antigenie, with the formation of basement membrane zone antibodies. "autoantibodies".