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

Utility of C4d Immunohistochemistry in the Diagnosis of Esophageal Pemphigus Vulgaris

Aims. To assess the utility of C4d immunohistochemistry for esophageal pemphigus vulgaris. Methods and results. We searched for patients with a history of esophageal pemphigus vulgaris who had esophageal biopsies for routine hematoxylin and eosin (H&E) staining. A total of 8 biopsies from 7 patients were available. We also identified 18 non-pemphigus esophageal biopsies for controls. C4d immunohistochemistry was performed on each biopsy. Five of 6 (83%) biopsies with classic pemphigus vulgaris histologic findings were positive for intercellular staining at the basal layer. The negative biopsy was in a patient that had recently received high-dose corticosteroid treatment for a flare. Two biopsies with atypical histologic features for pemphigus vulgaris had negative C4d staining but positive direct immunofluorescence (DIF) studies. Various nonspecific C4d staining patterns were observed in the controls, but none showed the intercellular staining pattern that was observed in pemphigus vulgaris. Conclusions. Suprabasal clefting with acantholysis and "tombstone effect" are described histologic features of pemphigus vulgaris on H&E. However, procedural artifact may mimic these findings. Currently, the gold standard for pemphigus vulgaris is DIF, which is not always available because it cannot routinely be performed on formalin-fixed paraffin embedded tissue. Our study shows that C4d immunohistochemistry may be a useful adjunct in evaluating esophageal pemphigus vulgaris.

Diagnosis of autoimmune bullous dermatoses: Comparative analysis of immunohistochemical staining using C4d, C3d, IgG, and IgG4 in lesional tissues and perilesional frozen skin samples

Immunohistochemical staining with immunoglobulins and complements may aid the diagnosis of patients whose clinical and histological findings are consistent with autoimmune bullous dermatoses (AIBD). We aimed to investigate the diagnostic value of immunohistochemical markers in lesional biopsy and perilesional frozen samples in AIBD. We included 136 cases from whom lesional biopsies and perilesional samples for direct immunofluorescence (DIF) examination were collected with a preliminary diagnosis of AIBD between January 2019 and January 2023. All diagnoses were reconfirmed by evaluating the clinical, histopathological, and serological findings and DIF results (C3, IgG, IgA, or IgM positivity compatible with the clinical diagnosis) altogether, although DIF results were considered a priority. After confirming the diagnoses, the samples were categorized as AIBD or the others. The perilesional tissues obtained for DIF simultaneously with skin biopsy and stored at -80 °C were thawed, and FFPE tissues were prepared. We performed immunohistochemical staining (C4d, C3d, IgG, and IgG4) on FFPE tissues of both lesional and perilesional samples. Strong, linear, or granular staining patterns at the dermoepidermal junction or the intraepidermal blistering space were considered positive in line with the diagnosis of the case. Cases other than AIBD were used as negative control tissues to assess the specificity of immunohistochemical markers. Of the 136 cases, 52 were diagnosed with AIBD. In lesional samples, the sensitivity of C4d, C3d, IgG, and IgG4 was 80.6 %, 69.4 %, 75 %, and 5.7 % with corresponding specificity of 100 %, 98.7 %, 89.6 %, and 97.4 %, respectively in pemphigoid diseases compared to a sensitivity of 18.2 %, 9.1 %, 70 %, and 9.1 % and specificity of 98.7 %, 100 %, 89.6 %, and 97.4 %, respectively in pemphigus diseases. In frozen samples, we detected expression in a limited number of cases. The sensitivity of C4d, C3d, IgG, and IgG4 was 8.7 %, 2.2 %, 19.4 %, and 2.2 %, with corresponding specificity of 100 %, 100 %, 98.5 %, and 98.6, respectively. There was a none to slight concordance rate between the IHC results of lesional tissues and perilesional frozen samples. Kappa coefficients for C4d, C3d, IgG, and IgG4 were 0.120 (P = 0.029), 0.111 (P = 0.050), 0.203 (P = 0.003), and - 0.15 (P = 0.846), respectively. Immunohistochemical staining with C4d, C3d, IgG, and IgG4 on biopsy samples collected from lesions may guide the diagnosis of AIBD, thereby eliminating the need for an additional biopsy and accelerating the diagnostic process.

C3d Immunohistochemical Staining on Paraffin-Embedded Tissue for Diagnosis of Pemphigus

CONTEXT.—

Pemphigus is an autoimmune blister disease that causes blisters on the skin and mucosal surfaces. Direct immunofluorescence (DIF) testing is critical for the clinical diagnosis of pemphigus. However, it is limited to fresh tissue specimens and fluorescence microscopy.

OBJECTIVE.—

To assess the value of C3d immunohistochemistry (IHC) on paraffin-embedded skin tissue for the diagnosis of pemphigus by comparing C3d-IHC results to DIF and enzyme-linked immunosorbent assay testing in pemphigus and other blister-related skin diseases.

DESIGN.—

C3d-IHC assays were retrospectively performed on paraffin-embedded skin tissue sections from 115 patients (63 with pemphigus and 52 controls). Both the case group and the control group underwent the same protocol, and cases with C3d position in the peripheral spinous layer were considered as positive samples.

RESULTS.—

C3d-IHC and DIF testing had similar performance for pemphigus diagnosis, with a sensitivity of 71.0% (95% CI, 51.8%-85.1%) and 77.4% (95% CI, 58.5%-89.7%), specificity of 96.4% (95% CI, 79.8%-99.8%) and 100% (95% CI, 85.0%-100%), positive predictive value of 95.7% (95% CI, 76.0%-99.8%) and 100% (95% CI, 82.8%-100%), and a negative predictive value of 75.0% (95% CI, 57.5%-87.3%) and 80.0% (95% CI, 62.5%-90.9%), respectively.

CONCLUSIONS.—

Our study indicated that C3d-IHC results for paraffin-fixed tissues were not significantly different from DIF results for the diagnosis of pemphigus. The C3d-IHC assay has the potential for routine diagnosis of pemphigus, especially in the absence of fresh-frozen tissue.

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.

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.

Applications of Model-Based Meta-Analysis in Drug Development

Model-based meta-analysis (MBMA) is a quantitative approach that leverages published summary data along with internal data and can be applied to inform key drug development decisions, including the benefit-risk assessment of a treatment under investigation. These risk-benefit assessments may involve determining an optimal dose compared against historic external comparators of a particular disease indication. MBMA can provide a flexible framework for interpreting aggregated data from historic reference studies and therefore should be a standard tool for the model-informed drug development (MIDD) framework.In addition to pairwise and network meta-analyses, MBMA provides further contributions in the quantitative approaches with its ability to incorporate longitudinal data and the pharmacologic concept of dose-response relationship, as well as to combine individual- and summary-level data and routinely incorporate covariates in the analysis.A common application of MBMA is the selection of optimal dose and dosing regimen of the internal investigational molecule to evaluate external benchmarking and to support comparator selection. Two case studies provided examples in applications of MBMA in biologics (durvalumab + tremelimumab for safety) and small molecule (fenebrutinib for efficacy) to support drug development decision-making in two different but well-studied disease areas, i.e., oncology and rheumatoid arthritis, respectively.Important to the future directions of MBMA include additional recognition and engagement from drug development stakeholders for the MBMA approach, stronger collaboration between pharmacometrics and statistics, expanded data access, and the use of machine learning for database building. Timely, cost-effective, and successful application of MBMA should be part of providing an integrated view of MIDD.

Unmet Medical Needs in Chronic, Non-communicable Inflammatory Skin Diseases

An estimated 20-25% of the population is affected by chronic, non-communicable inflammatory skin diseases. Chronic skin inflammation has many causes. Among the most frequent chronic inflammatory skin diseases are atopic dermatitis, psoriasis, urticaria, lichen planus, and hidradenitis suppurativa, driven by a complex interplay of genetics and environmental factors. Autoimmunity is another important cause of chronic skin inflammation. The autoimmune response may be mainly T cell driven, such as in alopecia areata or vitiligo, or B cell driven in chronic spontaneous urticaria, pemphigus and pemphigoid diseases. Rare causes of chronic skin inflammation are autoinflammatory diseases, or rheumatic diseases, such as cutaneous lupus erythematosus or dermatomyositis. Whilst we have seen a significant improvement in diagnosis and treatment, several challenges remain. Especially for rarer causes of chronic skin inflammation, early diagnosis is often missed because of low awareness and lack of diagnostics. Systemic immunosuppression is the treatment of choice for almost all of these diseases. Adverse events due to immunosuppression, insufficient therapeutic responses and relapses remain a challenge. For atopic dermatitis and psoriasis, a broad spectrum of innovative treatments has been developed. However, treatment responses cannot be predicted so far. Hence, development of (bio)markers allowing selection of specific medications for individual patients is needed. Given the encouraging developments during the past years, we envision that many of these challenges in the diagnosis and treatment of chronic inflammatory skin diseases will be thoroughly addressed in the future.

Diversity of complement activation in different thyroid diseases

OBJECTIVE

To investigate complement components expression in both thyroid tissues and serum from patients with Hashimoto's thyroiditis (HT), Graves' disease (GD), and papillary thyroid cancer (PTC).

METHODS

C1q, mannose binding lectin (MBL), Bb, C4d, C3d and membrane attack complex (MAC) (C5b-9) deposition and complement regulate proteins (CD46, CD55 and CD59) expression in thyroid tissues from HT, GD, PTC, and control groups were examined by IHC. C1q, MBL, Bb, C4d, C3a, and soluble C5b-9 (sC5b-9) serum levels in the HT, GD, PTC, and healthy donor (HD) groups were measured by ELISAs.

RESULTS

MAC deposition was detected in thyroid tissues in the HT, GD and PTC groups, but not the control group. MBL, Bb, C4d, C3d and MAC staining intensities in thyroid tissues were significantly higher in the HT and PTC groups than in the control group (all P < 0.05). The C1q level was higher in HT tissues than in control tissues (both P < 0.05). No complement component had a significant difference in staining intensities between the GD and control groups. CD55 and CD59 expression levels in thyroid tissues were higher in the PTC group than in the HT, GD and control groups (all P < 0.05). Similarly, CD46 levels were higher in HT tissues than in control tissues. Bb, C4d, C3a and sC5b-9 serum levels were significantly increased in HT, GD and PTC patients compared with HDs (all P < 0.05).

CONCLUSION

Complement is overactivated in HT and PTC, but not in GD. All the three pathways are activated in HT, and the MBL and alternative complement pathways are activated in PTC. These distinct complement activation profiles may participate in HT, GD and PTC pathogenesis.

Impact of adding an IgG4 conjugate to routine direct immunofluorescence testing for subepithelial and intraepithelial autoimmune blistering disorders

BACKGROUND

Certain autoimmune bullous dermatoses are mediated by autoantibodies of the IgG4 subclass. We determined the diagnostic impact of adding IgG4 to our conventional direct immunofluorescence (DIF) panel.

METHODS

For all cases submitted to our referral laboratory for DIF over 1 month (n = 630), we performed IgG4 testing and collected consecutive biopsy specimens showing definite or indeterminate linear or cell-surface deposition of IgG, IgG4, and/or C3. On retrospective blinded review, we classified the pattern and whether the findings were definite, indeterminate, or negative. When present, substantial background staining was recorded.

RESULTS

Seventy DIF specimens met the inclusion criteria. Of 22 (31.4%) specimens equivocal for linear or cell-surface deposition, 9 (40.9%) had definitive IgG4 findings, either linear (3 of 14 equivocal linear cases; 21.4%) or cell-surface (6 of 8 equivocal cell-surface cases; 75.0%). Background deposition was substantial in 14 cases (20.0%) for IgG but in none for C3 or IgG4.

CONCLUSION

IgG4 allowed the classification of over 40% of DIF cases that were otherwise equivocal by IgG and C3. IgG4 staining showed lower levels of non-specific background staining than IgG or C3. IgG4 appears to contribute most value in cases with cell-surface deposition or with equivocal linear IgG deposition and negative C3 results.