Immunohistochemical diagnosis of mucous membrane pemphigoid

C4d immunostaining facilitates differentiation of pemphigoid nodularis from prurigo nodularis

Pemphigoid nodularis and prurigo nodularis have similar clinicopathological features and are difficult to distinguish. Enzyme-linked immunosorbent assays (ELISA) and direct/indirect immunofluorescence can support the diagnosis of pemphigoid nodularis, but sometimes show contradictory results or are unavailable. We aimed to develop a practical method for differentiating between pemphigoid nodularis and prurigo nodularis. We analyzed the results of ELISA, direct immunofluorescence (DIF), and C3d and C4d immunohistochemistry (IHC) in 15 and 25 cases of pemphigoid nodularis and prurigo nodularis, respectively. C3d and C4d IHC results were positive in 8/15 (53.3 %) and 13/15 (86.7 %) patients with pemphigoid nodularis, respectively, and negative in all 25 patients with prurigo nodularis. The highest sensitivity (86.7 %) and negative predictive values (92.6 %) were observed in both C4d IHC and anti-BP180 ELISA, whereas C3d IHC exhibited the lowest sensitivity (53.3 %) and negative predictive values (78.1 %). Therefore, anti-BP180 ELISA and C4d IHC were the most sensitive markers to diagnose pemphigoid nodularis. The combination of DIF, ELISA, and C4d IHC is a relatively accurate panel of investigations for distinguishing pemphigoid nodularis from prurigo nodularis.

State-of-the-art diagnosis of autoimmune blistering diseases

Autoimmune blistering disorders (AIBDs) are a heterogeneous group of approximately a dozen entities comprising pemphigus and pemphigoid disorders and dermatitis herpetiformis. The exact diagnosis of AIBDs is critical for both prognosis and treatment and is based on the clinical appearance combined with the detection of tissue-bound and circulating autoantibodies. While blisters and erosions on the skin and/or inspectable mucosal surfaces are typical, lesions may be highly variable with erythematous, urticarial, prurigo-like, or eczematous manifestations. While direct immunofluorescence microscopy (IFM) of a perilesional biopsy is still the diagnostic gold standard, the molecular identification of the major target antigens opened novel therapeutic avenues. At present, most AIBDs can be diagnosed by the detection of autoantigen-specific serum antibodies by enzyme-linked immunosorbent assay (ELISA) or indirect IFM when the clinical picture is known. This is achieved by easily available and highly specific and sensitive assays employing recombinant immunodominant fragments of the major target antigens, i.e., desmoglein 1 (for pemphigus foliaceus), desmoglein 3 (for pemphigus vulgaris), envoplakin (for paraneoplastic pemphigus), BP180/type XVII collagen (for bullous pemphigoid, pemphigoid gestationis, and mucous membrane pemphigoid), laminin 332 (for mucous membrane pemphigoid), laminin β4 (for anti-p200 pemphigoid), type VII collagen (for epidermolysis bullosa acquisita and mucous membrane pemphigoid), and transglutaminase 3 (for dermatitis herpetiformis). Indirect IFM on tissue substrates and in-house ELISA and immunoblot tests are required to detect autoantibodies in some AIBD patients including those with linear IgA disease. Here, a straightforward modern approach to diagnosing AIBDs is presented including diagnostic criteria according to national and international guidelines supplemented by long-term in-house expertise.

Utility of C3d and C4d immunohistochemical staining in formalin-fixed skin or mucosal biopsy specimens in diagnosis of bullous pemphigoid and mucous membrane pemphigoid

Bullous pemphigoid (BP) and mucous membrane pemphigoid (MMP) sometimes have overlapping clinical, histopathological, and direct immunofluorescence (DIF) features in the early stages. Complement deposition is an intrinsic component of the patho-mechanism of BP in contrast to MMP. Hence immunohistochemistry (IHC) for C3d and C4d may be helpful in differentiating the two disorders. Seventy-four patients of BP and 18 patients of MMP along with 10 negative controls were enrolled in this study. C3d and C4d IHC was performed in formalin-fixed skin biopsy specimens. C3d IHC staining in BP/MMP had a sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of 59.2%/41.2%, 100%/100%, 100%/100%, 25.6%/50.0%, respectively. C4d IHC staining in BP/MMP had a sensitivity, specificity, PPV and NPV of 26.8%/17.6%, 100%/100%, 100%/100% and 16.1%/41.7%, respectively. Receiver operator analysis showed utility of C3d in diagnosing both BP [Area under curve (AUC) = 0.8, p = 0.0001] and MMP (AUC = 0.71; p = 0.001). C4d was useful in diagnosis of BP (AUC = 0.5; p = 0.0001), but not MMP (AUC = 0.6; p = 0.064). Hence, C3d is a better diagnostic modality for BP as compared to C4d, whereas C3d and C4d have lower diagnostic importance in MMP. C3d IHC can be employed in diagnosing BP when a second biopsy for direct immunofluorescence (DIF) is not possible or where a facility for IF microscopy does not exist.

Direct Immunofluorescence of IgG on Formalin-Fixed Paraffin-Embedded Tissue by Heat-Induced Antigen Retrieval as a Sensitive Method for the Diagnosis of Pemphigus

Purpose

Direct immunofluorescence (DIF) on frozen sections (DIF-F) plays a key role in the identification and differential diagnosis of bullous dermatoses, which are a group of critical autoimmune diseases that include pemphigus, bullous pemphigoid (BP), and epidermolysis bullosa acquisita (EBA). However, this technique requires specialized laboratory equipment conditions, sample acquisition and sample preservation. In this study, the application value of DIF on paraffin-embedded tissue sections (DIF-P) detecting IgG using heat-induced antigen retrieval (HIAR) in the diagnosis of bullous dermatosis was explored.

Patients and Methods

Samples from 12 patients with pemphigus vulgaris (PV), 10 patients with pemphigus foliaceus (PF), 17 patients with BP, and 4 patients with EBA were retrospectively studied for DIF-P IgG detection. Formalin-fixed, paraffin-embedded tissue (FFPE) was used, and the antigen retrieval method used in the experiment was HIAR. All patients were diagnosed with the autoimmune bullous disease (AIBD) based on clinical presentation, histopathology, DIF-F, and enzyme-linked immunosorbent assay (ELISA).

Results

Intercellular staining for IgG in the epidermis was successful in paraffin-embedded tissue sections in 11 of 12 PV samples and in all 10 PF samples. IgG at the basement membrane zone (BMZ) was not detected by immunofluorescent staining in 17 BP samples and 4 EBA samples.

Conclusion

The detection of IgG by DIF-P using HIAR can be used for the diagnosis of pemphigus as an alternative method to DIF-F.

Immunoglobulin and Complement Immunohistochemistry on Paraffin Sections in Autoimmune Bullous Diseases: A Systematic Review and Meta-analysis

ABSTRACT

Immunohistochemistry (IHC) on formalin-fixed, paraffin-embedded tissue has been proposed as a potential tool in the diagnosis of autoimmune bullous diseases (AIBDs) in lieu of standard direct immunofluorescence (DIF) microscopy. To comprehensively determine the diagnostic accuracy of immunoglobulin and complement IHC for diagnosis of AIBDs, we conducted a systematic review and multivariate Bayesian model-based meta-analysis of the literature. Quality and heterogeneity assessment of studies was performed using the Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) checklist and the I2 index, respectively. Electronic searches using PubMed from April 1964 to July 2020 identified 14 articles meeting predetermined inclusion and exclusion criteria. Median sensitivities with 95% credible intervals in pemphigus and pemphigoid were 0.24 (0.01-0.89) and 0.22 (0.02-0.77) with immunoglobulin G (IgG), 0.77 (0.39-0.95) and 0.25 (0.02-0.85) with IgG4, 0.11 (0.02-0.32) and 0.86 (0.56-0.98) with C3d, and 0.84 (0.56-0.97) and 0.75 (0.37-0.94) with C4d, respectively. Specificities were 1.00 (0.00-1.00) with IgG, 0.98 (0.89-1.00) with IgG4, 0.99 (0.97-1.00) with C3d, and 0.99 (0.97-1.00) with C4d. The risk of bias and heterogeneity among studies was a serious problem, decreasing the level of evidence. Our work suggests that, in selected cases, paraffin-based IHC may be a helpful procedure to screen for AIBDs, especially when specialized laboratories and/or biopsy specimens for DIF do not exist. Nevertheless, more studies with a refined quality design are needed to explore the true usefulness of this diagnostic method in AIBDs.

Deposition of resistant bacteria and resistome through FMT in germ-free piglets

Faecal microbiota transplantation (FMT) has received considerable attention in recent years due to its remarkable efficacy in restoring a normal gut microbiome. Here, we established the groups of post-FMT recipient piglets using germ-free piglets during early life to characterize the colonization of gut microbiota composition and the enrichment of resistance gene acquisition. By metagenomic analysis, we identified 115 bacterial phyla and 2111 bacterial genera that were acquired by the FMT recipients. We found that early-life microbial colonization and the spread of resistomes in recipient piglets were age dependent. A total of 425, 425 and 358 AR genes primarily belonging to 114, 114 and 102 different types were detected in the donors, post-FMT recipients in the FMT-3D group and post-FMT recipients in the FMT-15D group respectively. Genes that encoded tetracycline, macrolide and chloramphenicol resistance proteins were the most dominant AR genes, and the results corresponded with the exposure of antibiotic consumption at farm. Bacteroides, Escherichia, Clostridium, Parabacteroides, Treponema, Lactobacillus and Enterococcus were significantly correlated with the distribution of AR genes. More importantly, the relative abundance of AR genes was positively correlated with the levels of mobile genetic elements. Our results indicate that early-life microbial colonization can persistently shape the gut microbiota and antibiotic resistome.

[Modern diagnostics of autoimmune bullous diseases]

Blisters and erosions of skin and mucous membranes are key features of the clinically heterogeneous group of autoimmune bullous diseases (AIBDs). These can be divided into pemphigoid diseases with autoantibodies against structural proteins of the dermal-epidermal junction, pemphigus diseases with autoantibodies against desmosomal proteins, and dermatitis herpetiformis with autoantibodies against transglutaminases 1 and 2. A differentiation based only on clinical features is often not sufficient. After researching the literature in PubMed, the current diagnostic tools for AIBDs are summarized.AIBD diagnostics are performed using histology, direct and indirect immunofluorescence, as well as ELISA and immunoblotting. For serological diagnosis, the conventional multistep approach or multivariant assays for the analysis of autoantibodies against several target antigens in parallel can be applied. These allow a precise classification of AIBD and therefore a tailored use of different therapeutic regimens, e.g., for bullous pemphigoid or pemphigus foliaceus/vulgaris, as well as identification of disease entities with a known association with neoplasia.Direct immunofluorescence is still the diagnostic mainstay of AIBDs. However, novel serological assays, such as target-antigen-specific ELISA or indirect immunofluorescence systems using BIOCHIP™ mosaic technology, allow serologic diagnosis in most AIBD patients and the exact classification of the disease entity at the molecular level.

Immunological methods for the diagnosis of oral mucosal diseases

Immunological methods, which have been widely used in autoimmune blistering diseases (AIBDs) of the oral mucosa, can also be adopted as auxiliary diagnostic tools in oral lichen planus (OLP) and discoid lupus erythematosus (DLE). AIBDs, characterized by autoantibodies against structural proteins of keratinocytes or the basement membrane zone, clinically present as blisters and erosions of the oral mucosa. When atypical lesions occur, OLP or DLE may be confused with AIBDs. The improvement of diagnostic accuracy is necessary due to the significant differences in treatment and prognosis among these diseases. A variety of immunological methods are used for qualitative and quantitative detection of target antigens and autoantibodies. These methods can evaluate efficacy of treatment, monitor diseases and guide treatment decisions. In this review, we discuss the application of immunofluorescence, biochemical tests, and protein microarrays for AIBDs, OLP and DLE, as well as the differential diagnostic methods using immunological tests.

The Diagnosis and Blistering Mechanisms of Mucous Membrane Pemphigoid

Mucous membrane pemphigoid (MMP) is a mucous membrane-dominated autoimmune subepithelial blistering disease that is caused by autoantibodies against various autoantigens in basement membrane zone (BMZ) proteins, including collagen XVII (COL17). Clinicians face diagnostic problems in detecting circulating antibodies and targeted antigens in MMP. The diagnostic difficulties are mainly attributed to the low titers of MMP autoantibodies in sera and to heterogeneous autoantigens. Additionally, no unanimous diagnostic criteria have been drawn for MMP, which can result in delayed diagnoses or misdiagnoses. This review aims to integrate and present currently available data to clarify diagnostic strategies and to present diagnostic criteria for MMP. The ultimate blistering mechanism in MMP has not been elucidated, and such mechanism is especially obscure in COL17-type MMP. In bullous pemphigoid (BP), which is the most common autoimmune subepidermal blistering disease, some patients show oral lesion as well as predominant skin lesions. However, there is no fundamental explanation for the onset of oral lesions in BP. This article summarizes innovative research perspectives on the pathogenesis of oral lesions in pemphigoid. Finally, we propose a potential pathogenesis for COL17-type MMP.