Involvement of Nail Apparatus in Pemphigus Vulgaris in Ethnic Poles Is Infrequent

The diagnostic gold standard of autoimmune bullous diseases is the detection of autoantibodies in skin or mucous membranes by direct immunofluorescence microscopy of a perilesional biopsy. The molecular characterisation of several target antigens within the last 10 years has, however, fostered the development of sensitive and specific diagnostic tools that allow the serological diagnosis in about 90% of patients. Based on the recombinant immunodominant portions of the target antigens, ELISA systems are commercially available for the detection of circulating antibodies against desmoglein 1, desmoglein 3, envoplakin, BP180, and BP230. Autoantibodies against the soluble ectodomain of BP180 (LAD-1), laminin 332, type VII collagen, and most recently, laminin γ1 can be detected by Western blotting with recombinant or cell-derived forms of these proteins. The definite differentiation between the various immunobullous disorders that comprise about a dozen entities is increasingly important since more diverse treatment options are employed. Exact diagnosis is also pivotal for the prognosis, since some autoimmune bullous diseases may indicate an underlying tumor. Association with a malignancy has been shown in paraneoplastic pemphigus (in 100%) and anti-laminin 332 mucous pemphigoid (in 25%) In pemphigus vulgaris, pemphigus foliaceus, and bullous pemphigoid, autoantibodies to desmoglein 3, desmoglein 1, and BP180, respectively, have been shown to correlate with the disease activity. The detection of serum autoantibodies during the course of the disease may thus be helpful in guiding treatment decisions in these patients. Copyright © 2010 Elsevier B.V. All rights reserved.

Background Various antigen-specific immunoassays are available for the serological diagnosis of autoimmune bullous diseases. However, a spectrum of different tissue-based and monovalent antigen-specific assays is required to establish the diagnosis. BIOCHIP mosaics consisting of different antigen substrates allow polyvalent immunofluorescence (IF) tests and provide antibody profiles in a single incubation. Methods Slides for indirect IF were prepared, containing BIOCHIPS with the following test substrates in each reaction field: monkey esophagus, primate salt-split skin, antigen dots of tetrameric BP180-NC16A as well as desmoglein 1-, desmoglein 3-, and BP230gC-expressing human HEK293 cells. This BIOCHIP mosaic was probed using a large panel of sera from patients with pemphigus vulgaris (PV, n = 65), pemphigus foliaceus (PF, n = 50), bullous pemphigoid (BP, n = 42), and non-inflammatory skin diseases (n = 97) as well as from healthy blood donors (n = 100). Furthermore, to evaluate the usability in routine diagnostics, 454 consecutive sera from patients with suspected immunobullous disorders were prospectively analyzed in parallel using a) the IF BIOCHIP mosaic and b) a panel of single antibody assays as commonly used by specialized centers. Results Using the BIOCHIP mosaic, sensitivities of the desmoglein 1-, desmoglein 3-, and NC16A-specific substrates were 90%, 98.5% and 100%, respectively. BP230 was recognized by 54% of the BP sera. Specificities ranged from 98.2% to 100% for all substrates. In the prospective study, a high agreement was found between the results obtained by the BIOCHIP mosaic and the single test panel for the diagnosis of BP, PV, PF, and sera without serum autoantibodies (Cohen’s κ between 0.88 and 0.97). Conclusions The BIOCHIP mosaic contains sensitive and specific substrates for the indirect IF diagnosis of BP, PF, and PV. Its diagnostic accuracy is comparable with the conventional multi-step approach. The highly standardized and practical BIOCHIP mosaic will facilitate the serological diagnosis of autoimmune blistering diseases.

The nail apparatus is constantly exposed to environmental damage. It requires effective immune responses to combat infection, while avoiding the loss of nail production and regeneration by autoaggressive immunity. By immunohistology, we define here previously unknown characteristics of the normal human nail immune system (NIS). Compared with other regions of nail epithelium, human leukocyte antigen (HLA)-A/B/C expression is prominently down regulated on both keratinocytes and melanocytes of the proximal nail matrix (PNM), whereas HLA-G(+) is upregulated here. Together with the expression of macrophage migration inhibitory factor in PNM, this may serve to inhibit an natural killer (NK) cell attack on major histocompatibility complex (MHC) class Ia-negative PNM. PNM also displays strong immunoreactivity for potent, locally generated immunosuppressants such as transforming growth factor-beta1, alpha-melanocyte stimulating hormone, insulin-like growth factor-1, and adrenocorticotropic hormone, exhibits unusually few CD1a(+), CD4(+), or CD8(+), NK, and mast cells. Finally, MHC class II and CD 209 expression on CD1a(+) cells in and around the PNM is reduced, indicating diminished antigen-presenting capacity. Thus, the NIS strikingly differs from the skin immune system, but shows intriguing similarities to the hair follicle immune system, including the establishment of an area of relative immune privilege in the PNM. This nail immune privilege may offer a relative safeguard against autoimmunity. But, the localized intraepithelial defect of innate and adaptive immunity in the PNM revealed here also may impede effective anti-infection defense.