Bullous pemphigoid, the most common autoimmune subepidermal bullous disorder, is associated with autoantibodies targeting antigenic sites clustered within the extracellular domain of BP180. To investigate epitope and subclass specificity of autoantibodies in bullous pemphigoid, we developed an enzyme-linked immunosorbent assay utilizing baculovirus-expressed recombinant forms of the NH2- and COOH-terminal regions of the extracellular domain of BP180 and examined sera obtained from patients with active bullous pemphigoid (n=116) and controls (n=100). Ninety-three (80%) and 54 (47%) of the 116 bullous pemphigoid sera recognized the NH2- and COOH-terminal regions, respectively, of the extracellular domain of BP180. Detailed analysis demonstrates that (i) this novel enzyme-linked immunosorbent assay is highly specific (98%) and sensitive (93%) as 108 of 116 bullous pemphigoid sera reacted with at least one of the baculovirus-derived recombinants, (ii) in active bullous pemphigoid, autoantibodies against the NH2-terminus of the extracellular domain of BP180 were predominantly of the IgG1 class, whereas a dual IgG1 and IgG4 response to this region was related to a more severe skin involvement, (iii) autoreactivity against both the NH2- and COOH-terminal regions was more frequently detected in patients with mucosal lesions, and (iv) levels of IgG (and IgG1) against the NH2-terminal, but not against the COOH-terminal portion of the extracellular domain of BP180, reflected disease severity indicating that autoantibodies against the NH2-terminus are critical in the pathogenesis of bullous pemphigoid. In conclusion, this novel enzyme-linked immunosorbent assay represents a highly sensitive and specific assay for rapid diagnosis of bullous pemphigoid and related disorders and may provide predictive parameters for the management of bullous pemphigoid patients.

Pemphigus vulgaris (PV) is the most severe autoimmune bullous skin disorder and is primarily associated with circulating autoantibodies (autoAb) against desmoglein 3 (Dsg3). In light of recent evidence that autoreactive T cells are critical for the induction and regulation of Ab production, the goal of this study was to characterize and quantitate autoreactive T cells in patients with PV and healthy controls. Peripheral Dsg3-reactive Th cells from 28 patients with acute-onset, chronic active, and remittent PV were quantitated by MACS secretion assay. Dsg3-reactive Th2 cells were detected at similar frequencies in all studied PV patients, while the number of autoreactive Th1 cells exceeded those of Th2 cells in chronic active PV. In contrast, healthy carriers of the PV-associated HLA class II alleles, DRB1*0402 and DQB1*0503, exhibited exclusively Dsg3-reactive Th1 cell responses, while healthy carriers of other HLA class II alleles did not. Moreover, the presence of IgG1 and IgG4 against Dsg3 was directly related to the ratio of Dsg3-reactive Th1/Th2 cells. T cell recognition of Dsg3 was restricted by HLA-DRB1*0402 and DQB1*0503 in PV patients and Dsg3-responsive healthy donors. These observations strongly suggest 1) that the appearance of Dsg3-reactive Th2 cells is restricted to patients with PV; 2) that specific HLA class II alleles that are prevalent in PV are critical for T cell recognition of Dsg3 in PV patients and Dsg3-responsive healthy donors; and 3) that autoAb production is associated with both Th1 and Th2 cells.

Immunoadsorption with tryptophan-linked polyvinylalcohol adsorbers holds promise as a highly effective and safe adjuvant therapeutic regimen in pemphigus.