IgA basement membrane zone autoantibodies in bullous pemphigoid detect epidermal antigens of 270-280 kDa, 230 kDa, and 180 kDa molecular weight by immunoblotting

The relationship between bullous pemphigoid and renal disease and related treatments: a review of the current literature

INTRODUCTION

Bullous pemphigoid (BP) is the most common autoimmune subepidermal blistering disorder in older adults. There is increasing evidence that BP has connections with renal diseases, such as glomerulopathy and neoplasm; it is also linked to the receipt of renal replacement therapy.

AREAS COVERED

In this review, we summarize the current evidence that BP is a comorbidity of common renal diseases. Furthermore, our exploration of the characteristics and possible mechanisms underlying these connections provides insights that may facilitate the prevention, diagnosis, and management of BP.

EXPERT OPINION

There is mounting proof that BP is not just a skin immunological disorder but rather a systemic immune-mediated illness. Quantities of case reports focused on BP as a renal disease comorbidity and the coexistence of them is not accidental. However, the underlying mechanisms are still needed to be investigated. Clinicians should be alert to the comorbidities in order to facilitate effective treatment and improve patient prognosis.

Risk Factors for Mucosal Involvement in Bullous Pemphigoid and the Possible Mechanism: A Review

Bullous pemphigoid (BP) is the most common type of autoimmune bullous disease and is characterized by the presence of circulating anti-BP180 and/or anti-BP230 autoantibodies. Patients with BP often present with tense blisters and erythema, mainly on the trunk and limbs, but a few patients also have mucosal involvement. In this article, we discuss the fact that BP patients with mucosal involvement tend to have more serious conditions and their disease is more difficult to control. Potential risk factors for mucous involvement include earlier age at onset, drugs such as dipeptidyl peptidase-4 inhibitors, cancer, and blood/serum biomarkers, including lower eosinophil count, higher erythrocyte sedimentation rate, IgG autoantibodies against both the NH₂- and COOH-termini of BP180, and the absence of anti-BP230 antibodies. IgA and C3 deposition at the dermo-epidermal junction may also be present. Understanding these risk factors may benefit earlier diagnosis of these patients and promote the development of novel treatments. What's more, it's helpful in deeper understanding of BP development and the relationship between BP and mucous membrane pemphigoid (MMP).

A 62-year-old man with new-onset bullae

Cutaneous blisters and/or bullae can occur in autoimmune disorders, infections, genetic diseases, and drug hypersensitivity. We present the case of a 62-year-old man with two autoimmune conditions who was admitted for antibiotic treatment of a lower extremity infection and suddenly developed a bullous rash. His physical examination was significant for tense, bullous lesions that involved his chin, palms, and inner thighs. Narrowing the differential diagnosis for patients with blistering skin lesions is imperative for timely and appropriate management.

IgA autoantibodies in the pemphigoids and linear IgA bullous dermatosis

BACKGROUND

Patients with bullous pemphigoid (BP), mucous membrane pemphigoid (MMP) and pemphigoid gestationis (PG) have IgG antibodies against BP180 and BP230, components of the hemidesmosomes. Patients with linear IgA bullous dermatosis (LABD) have IgA autoantibodies against a 97/120-kDa protein which is highly homologous to a shedded fragment of the BP180-ectodomain.

OBJECTIVES

The aim of our study was to determine the incidence of IgA autoantibodies directed against BP180/BP230 in the pemphigoids and LABD and to determine the antigenic regions that are targeted by IgA autoantibodies.

METHODS

Utilizing baculovirus-expressed recombinant BP180 and BP230 proteins, we performed immunoblot analyses for IgA reactivity of sera from patients with BP (n = 30), MMP (n = 10), PG (n = 6), LABD (n = 6) and from control patients with non-related pruritic dermatoses (n = 8).

RESULTS

IgA reactivity against BP180 and/or BP230 was detected in 19/30 of the BP, in 7/10 of the MMP, in 6/6 of the LABD and in 3/6 of the PG sera, respectively, but not in the control group. In all subgroups, the major antigenic site recognized by IgA antibodies was located within the NH(2)-terminus of the BP180-ectodomain, but only a minority of the sera showed also IgA reactivity against the BP180-NC16a-domain. IgA reactivity against the central domain of BP180 was more frequently seen than against its COOH-terminus. IgA against the COOH- and NH(2)-terminus of BP230, respectively, was detected in 6/30 of the BP, 1/10 of the MMP, 1/6 of the LABD and 0/8 control sera.

CONCLUSION

IgA reactivity against BP180 and/or BP230 is a common finding in the pemphigoids.

Vesicular pemphigoid with circulating autoantibodies against 230-kDa and 180-kDa proteins, and additional autoantibodies against 97-kDa and 45-kDa proteins

The vesicular variant of bullous pemphigoid is a clinical entity in which the principal type of lesions are multiple small tense vesicles in a symmetric distribution, instead of the classical large, more randomly distributed large bullae. We describe a 62-year-old female who developed a vesicular variant of bullous pemphigoid, with intensely pruritic vesiculopapular eruptions and erythematous irregularly outlined patches confluent on the face, neck, trunk, extremities and oral mucosa. Direct immunofluorescence revealed a linear deposition of IgG and C3 at the basement membrane zone of the skin, and indirect immunofluorescence detected circulating IgG autoantibodies reacting with antigens located on the epidermal side of skin split with 1 M NaCl. Indirect immunogold electron microscopy revealed IgG deposition at the underneath membrane of the basal cells and in the lamina lucida. In addition to the 230-kDa and 180-kDa bullous pemphigoid antigen, immunoblot analysis also demonstrated the presence of IgG antibodies reactive with 97-kDa and 45-kDa protein. Treatment with systemic corticosteroid, minocycline and antihistamines plus topical steroid resulted in moderate improvement. A few vesicles, however, continued to appear intermittently during the past year of treatment.

Increased expression of Th2-associated chemokines in bullous pemphigoid disease. Role of eosinophils in the production and release of these chemokines

Bullous pemphigoid is an inflammatory disease of the skin associated with eosinophil infiltration and the presence of high levels of Th2 cytokines in the associated blister fluid. Little is known about the contribution of chemokines in this disease. We found that eotaxin and MCP-4 mRNA and immunoreactivity were expressed in all biopsies of BP patients and were mainly localized to the epidermis and eosinophils. The expression of eotaxin and MCP-4 was enhanced in eosinophils following IL-5 treatment. Subsequent stimulation of IL-5-primed eosinophils with Ig-immune complexes, results in increase secretion of eotaxin and MCP-4 in the supernatants. Using immunostaining, these two chemokines were localized to the granules of eosinophils. BF was found to contain chemotactic activity for eosinophils, neutrophils and T cells. The chemotactic effect of BF for eosinophils was more effective when eosinophils were stimulated with IL-5 or IL-4. We also found that the levels of Th(2)-associated chemokines (eotaxin and MCP-4) in BF were significantly higher than the Th(1)-associated chemokines (MIP-1beta and IP-10). This was consistent with the increased chemotaxis of polarized Th(2) cells toward BF, when compared to Th(1)-differentiated T cells. Our results support the involvement of Th(2)-associated chemokines in the pathogenesis of BP disease.

Bullous Pemphigoid

Bullous pemphigoid (BP) is a chronic, autoimmune, blistering disease observed primarily in the elderly population. Several clinical variants have been described, including classic (bullous), localised, nodular, vegetating, erythrodermic, erosive, childhood and drug-induced forms. Autoantibodies target the BP230 and BP180 antigens, located in the hemidesmosomal complex of the skin basement membrane zone. Subsequent complement activation recruits chemical and cellular immune mediators to the skin, ultimately resulting in blister formation. Both autoantibodies and complement may be detected by various immunofluorescent, immune electron microscopy and molecular biology techniques. Recent trials suggest that potent topical corticosteroids should be considered as first-line therapy. Tetracycline with or without nicotinamide may benefit a subset of patients with mild BP. Oral corticosteroids should rarely exceed 0.75 mg/kg/day and corticosteroid-sparing agents may be useful for recalcitrant disease.

A comparative study of antibody titers of blister fluid and serum in patients with subepidermal immunobullous diseases

BACKGROUND

Subepidermal autoimmune bullous diseases (SABD) comprise several disorders, such as bullous pemphigoid (BP), cicatricial pemphigoid (CP), epidermolysis bullosa acquisita (EBA), herpes gestationis (HG), and linear immunoglobulin A (IgA) dermatosis (LAD), and are characterized by antibody production against the basement membrane structures of the skin and mucosa. Although indirect immunofluorescence (IIF) on serum is a routine test for the detection of basement membrane zone antibodies, there have only been a few studies related to IIF on blister fluid. Aim To perform IIF on blister fluid and to compare the results with those of serum.

METHODS

IIF on salt-split skin was performed on the serum and blister fluid of 35 patients with SABD (25 bp, three EBA, three HG, three LAD, and one bullous systemic lupus erythematosus) with conjugated IgG, IgA, and C3.

RESULTS

Twenty-eight of the 35 patients showed IIF-positive blister fluid with a titer similar or less than that of serum. In 25 patients with BP, the most common disease in this study, 23 cases (92%) had positive IIF on serum, 23 cases (92%) on blister fluid, and 24 cases (96%) on either serum or blister fluid. Immunoreactant titers in BP blister fluid and serum did not show significant differences (P > 0.05). Epidermal binding of immunoreactants was the most prevalent staining pattern of IIF on salt-split skin (92%) in BP.

CONCLUSIONS

From the findings of this study, the blister fluid of patients with SABD can be used for IIF. Although IIF sensitivity on blister fluid is no more than that on serum, the performance of this test on blister fluid in addition to serum may reduce the number of false negative results of IIF found using either of these two substrates alone.

Linear IgA disease: the IgA and IgG response to the epidermal antigens demonstrates that intermolecular epitope spreading is associated with IgA rather than IgG antibodies, and is more common in adults

BACKGROUND

Linear IgA disease (LAD; adult and childhood) is a dapsone-responsive, acquired immunobullous disorder mediated by IgA antibodies directed at target antigens within the epithelial basement membrane. These antigens have not been completely characterized.

OBJECTIVES

To identify the target antigens in LAD, and to correlate these with the antibody isotype.

METHODS

We used 101 LAD sera without IgG antibodies detected by indirect immunofluorescence. The sera were analysed by immunoblotting for IgA (65 adults and 36 children) and IgG (61 adults and 34 children) autoantibodies, on salt-split, urea-extracted epidermal tissue extracts.

RESULTS

Antigens were targeted in LAD by IgA antibodies (54 adults and 23 children), IgG antibodies (34 adults and 19 children), and both isotypes (30 adults and 16 children). Three major antigens were recognized by IgA antibodies: LAD285 (22 adults and three children), BP230 (30 adults and eight children) and BP180 (collagen XVII), including the 97-kDa ectodomain (52 adults and 20 children). Seven 'minor' antigens were occasionally detected (18 adults and 13 children). IgA antibodies bound multiple antigens (33 adults and nine children) more frequently than single antigens (21 adults and 14 children), but the binding to multiple antigens was more restricted in children than in adults. IgG antibodies mainly bound a single antigen (29 adults and 16 children), predominantly BP180.

CONCLUSIONS

There was variation in the autoantibody response within the disease and the patient, with regard to target molecules and autoantibody class. The finding that IgG as well as IgA autoantibodies predominantly target BP180 supports a pivotal role for collagen XVII in adult and childhood LAD. The IgG response was very restricted compared with IgA autoantibodies (P < 0.01). Autoantibodies from children had a more restricted antigen repertoire than from adults (P < 0.05). Epitope spreading is common in LAD and is affected by the class of autoantibody and age of the patient.

Mixed immunobullous disease of childhood: a good response to antimicrobials

BACKGROUND

Immunobullous diseases are uncommon in childhood. In contrast to adults, the most commonly seen is IgA-mediated chronic bullous disease of childhood (CBDC), while IgG-mediated bullous pemphigoid (BP), cicatricial pemphigoid (CP) and epidermolysis bullosa acquisita (EBA) are rare. We have demonstrated both IgG and IgA autoantibodies to basement membrane zone target antigens in eight children with 'mixed immunobullous disease of childhood'.

OBJECTIVES

To elucidate whether a dual antibody response makes these patients distinct regarding their presentation, immunopathology, course and prognosis.

METHODS

We compared the eight children showing the double antibody response with 62 children with CBDC, BP, CP and EBA in whom only one antibody isotype was demonstrated. Clinical information at presentation, clinical course and response to treatment were recorded, and immunoblotting and direct and indirect immunofluorescence (IF) were performed.

RESULTS

Six of the eight patients presented with clinical features of CBDC. In two others, it was uncertain whether they had CBDC or BP. Seven of the eight demonstrated a dual antibody response on indirect IF and three on direct IF. Immunoblotting revealed a variety of epidermal and dermal target antigens (BP230, BP180, 97-kDa protein and laminin 5). Five of the eight responded well to dapsone, two to sulphonamides, and one to systemic erythromycin alone. The clinical course was not protracted. Five are in remission 1-4 years following treatment, and three still have active disease suppressed by treatment after 6 months-2 years.

CONCLUSIONS

Although we do not know why these children have 'mixed immunobullous disease' (the dual antibody response), our results indicate that the presence of IgA is associated with a good response to treatment with antimicrobials (dapsone, sulphonamides, erythromycin), and the clinical course is no more protracted than that found in children with a single antibody response.

Patients with bullous pemphigoid and linear IgA disease show a dual IgA and IgG autoimmune response to BP180

Bullous pemphigoid (BP) and linear IgA disease (LAD) are autoimmune subepidermal blistering skin diseases associated with autoantibodies against the transmembrane hemidesmosomal protein BP180/type XVII collagen. It has been demonstrated previously that BP is characterized predominantly by IgG autoantibodies, while autoantibodies in LAD mainly belong to the IgA isotype. The aim of the present study was to investigate the hypothesis that there is a significant overlap in the autoantibody isotype profiles associated with these two diseases. Several new recombinant forms of BP180 were generated in the baculovirus expression system, including the full-length protein. IgG autoantibodies to BP 180 were detectable in 39 of 40 (98%) of BP sera; interestingly, 88% of BP sera also contained IgA anti-BP180 autoantibodies. Similarly, anti-BP180 reactivity in LAD sera (n=22) was also attributed to both an IgA (68%) and an IgG (76%) autoantibody response. IgA and IgG autoantibodies to the intracellular portion of BP180 were found in 14% and 28% of BP sera, respectively, and in 8% of LAD sera (same percentage for both isotypes). Our findings clearly demonstrate that both BP and LAD patients have a dual IgA and IgG autoimmune response to BP180 which is directed not only to the ectodomain, but also to the intracellular portion of this protein.

IgG, IgA and IgE autoantibodies against the ectodomain of BP180 in patients with bullous and cicatricial pemphigoid and linear IgA bullous dermatosis

BACKGROUND

Bullous pemphigoid (BP), linear IgA bullous dermatosis (LABD) and cicatricial pemphigoid (CP) are clinically distinct autoimmune bullous skin diseases characterized by autoantibodies against components of the epidermal basement membrane. Like most patients with BP, a significant subgroup of patients with CP has circulating IgG specific for BP180, a transmembraneous protein of hemidesmosomes. Moreover, sera of patients with LABD contain IgA autoantibodies reactive with a 97/120-kDa protein, LABD antigen 1, which is highly homologous to the extracellular portion of BP180.

OBJECTIVES

We aimed to determine whether, in these diseases, autoantibody reactivity to BP180 is restricted to distinct immunoglobulin subtypes.

METHODS

Utilizing a baculovirus-encoded form of the ectodomain of BP180, sera from patients with BP (n = 10), CP (n = 9), LABD (n = 10) and normal human control sera (n = 10) were analysed by immunoblot for IgG, IgA and IgE reactivity against BP180.

RESULTS

All of 10 BP sera displayed IgG, IgA and IgE reactivity with BP180. Six and seven of nine CP sera, respectively, contained IgG and IgA autoantibodies reactive with BP180, but none of nine sera contained BP180-specific IgE. Nine of 10 LABD sera contained IgA, and six of 10 IgG, which was reactive with BP180, but none of 10 sera showed IgE reactivity to BP180.

CONCLUSIONS

The presence of IgG and IgA autoantibody responses to BP180 in patients with three clinically distinct autoimmune bullous diseases indicates that an autoimmune response to the same distinct adhesion protein may lead to different clinical manifestations. It is therefore conceivable that variable epitopes of BP180 are targeted by the different autoantibody isotypes, resulting in the distinct clinical pictures.