Antibody-induced proteinase activation: a proposed mechanism for pemphigus

Clinical and Laboratory Evaluation of Hemocarboadsorption in Autoimmune Bullous Dermatoses

Hemocarboadsorption (HCA) with the following immunosuppressive therapy was used to treat 48 patients with pemphigus vulgaris (PV) and 31 patients with bullous pemphigoid (BP) in the acute phase. The levels of autoantibodies, eicosanoids, endoproteases and their inhibitors as well as interleukin (IL) 1 and IL 2 production and absorption of exogenous IL 2 were examined in the treatment dynamics. The therapeutic effect of HCA was displayed in prompt disease remission in 43 PV and 29 BP patients. Clinical improvement was accompanied by antibody elimination and interleukin cascade reaction normalization. HCA resulted in growth of patients’ serum immunosuppressive activity. It was concluded that HCA has some immunoregulatory effect.

Changes in connective tissue macromolecular components of Yucatan mini-pig skin following application of sulphur mustard vapour

1. The aim of this study was to determine the nature of the macromolecular alterations in Yucatan mini-pig skin which occur following application of sulphur mustard vapour, with particular reference to laminin and type IV collagen. 2. The immunostaining of transfer blots from skin extracts run on SDS-PAGE gels revealed no evidence of cross-linking of type IV collagen or laminin. Laminin was, however, found to be partially degraded as determined by the resolution of 132 and 143 kDa fragments, possibly by the activation of proteases, following the application of sulphur mustard to pig skin. Type IV collagen was not subject to this form of degradation in the skin samples exposed to sulphur mustard. 3. Yucatan mini-pig skin was found to develop microblisters after exposure to sulphur mustard vapour. The immunohistochemical studies of sulphur mustard exposed skin revealed that separation of the epidermis from the dermis was found to occur within the lamina lucida of the subepidermal basement membrane, supporting the contention that cleavage of laminin networks occurs following mustard challenge. Immunohistochemical staining with anti-type IV collagen antibodies was restricted to the floor of the micro-blister lesions. 4. The results suggest that laminin may be a target for protease activation at the dermo-epidermal junction. This may account for the tendency of certain skin models to develop sulphur mustard-induced blistering. The Yucatan mini-pig may be valuable as a model to determine the efficacy of prophylactic and therapeutic regimes.

Specificity and cross-reactive idiotypes of anti-glomerular basement membrane autoantibodies in HgCl2-induced autoimmune glomerulonephritis

Mercury-induced autoimmune glomerulonephritis in the Brown-Norway (BN) rat is characterized by the successive appearance of linear and granular glomerular IgG deposits. Anti-laminin autoantibodies represent the major part of the anti-glomerular basement membrane (GBM) antibodies produced in this model. Fusions were performed in this model and four anti-GBM monoclonal antibodies (mAb) were obtained. Three of them were laminin specific. Using rabbit anti-idiotype antibodies, cross-reactive idiotypes (CRId) were characterized on anti-laminin antibodies. They were expressed on the three anti-laminin mAb, on kidney-eluted and circulating anti-laminin antibodies. CRId-bearing immunoglobulins were detected transiently in the circulation and paralleled the anti-laminin antibody activity. By immunofluorescence studies on kidney cryostat sections two different CRId were defined. One was localized close to the antigen-combining site since it was not revealed on kidney-bound antibodies, in contrast with the second CRId. This latter CRId was also found deposited in a typical linear pattern in the early phase of the disease and in a granular pattern in the late phase, demonstrating that these CRId are components of immune deposits. Taken together, these results suggest that in this model of T-dependent polyclonal B cell activation, restricted sets of V genes encode for at least a part of the anti-GBM autoantibodies.

Anti-cell surface pemphigus autoantibody stimulates plasminogen activator activity of human epidermal cells. A mechanism for the loss of epidermal cohesion and blister formation

Binding of anti-cell surface pemphigus autoantibodies to cultured human epidermal cells stimulates synthesis and secretion of plasminogen activator (PA). Increases in PA activity were detected within 6 h of the addition of IgG and stimulation was dependent upon IgG concentration. Stimulation of PA activity was inhibited by cycloheximide, which indicates that synthesis of protein was necessary. Pharmacological doses of dexamethasone also prevented IgG-induced stimulation of PA. Electrophoretic profiles of PA secreted by cultured human epidermal cells in the presence or absence of pemphigus IgG were similar. The majority of the PA activity comigrated with the higher-molecular-weight species of human urokinase (approximately 55,000). Explants of normal human skin incubated with pemphigus vulgaris IgG displayed loss of epidermal cohesion similar to that observed in patient biopsies. The histologic changes were potentiated by the inclusion of human plasminogen. Loss of epidermal cohesion in normal skin explants incubated with pemphigus foliaceous IgG was dependent upon the addition of plasminogen and was inhibited by aprotinin or lima bean trypsin inhibitor, which indicated that plasmin is the active enzyme in producing acantholysis. These data support the hypothesis that stimulation of PA by the anti-cell surface autoantibodies of pemphigus results in a localized increase in plasmin, which through proteolysis produces the loss of epidermal cohesion characteristic of pemphigus.

Autodegradation of 125I-labeled human epidermal cell surface proteins

Triton X-100 extracts of cultured human epidermal cells exhibited proteolytic activity as measured by the hydrolysis of [3H]-casein at neutral pH. The majority of endogenous proteolytic activity was inhibited by parahydroxy mercuribenzoate and by mersalyl acid, indicating the enzyme(s) was a thiol class proteinase(s). Crude Triton X-100 extracts were prepared from epidermal cells following labeling of proteins with 125I. Autodegradation of labeled proteins at 37 degrees C was detected as early as 1 hr and reached a plateau level by 4 hr. Degradation was inhibited by thiol class proteinase inhibitors. Among the detergent-solubilized radiolabeled proteins a polypeptide chain of Mr 155,000 was particularly sensitive to degradation by endogenous thiol proteinase(s).