Identification and characterization of autoreactive T cell responses to bullous pemphigoid antigen 2 in patients and healthy controls

Mucous membrane pemphigoid: HLA-DQB1*0301 is associated with all clinical sites of involvement and may be linked to antibasement membrane IgG production

BACKGROUND

Class I human leucocyte antigens (HLA) -A, -B, -Cw and class II HLA-DRB1, -DQB1 alleles were determined in 131 British Caucasian patients with mucous membrane pemphigoid (MMP) using serological and DNA-based methods.

OBJECTIVES

To analyse the class I and II alleles expressed in well-defined clinical and immunopathological subgroups of MMP, in order to establish whether specific alleles or haplotypes might in part explain disease susceptibility, clinical sites of involvement or disease severity.

METHODS

Subgroups of patients were analysed according to the following clinical criteria: age of onset, sex, sites of clinical involvement (oral, ocular, skin, nasal, genital, pharyngeal, oesophageal, laryngeal, perianal), disease severity and history of autoimmune disease. Subgroups were also analysed according to the following immunopathological criteria: autoantibody profile, the presence of circulating antibasement membrane IgG or IgA antibodies and the detection of target basement membrane zone (BMZ) antigens (BP230 and BP180) by IgG autoantibodies.

RESULTS

Class I HLA typing showed no significant disease or subgroup associations. Class II DRB1 typing showed a significantly increased allelic frequency in MMP vs. controls for DRB1*11 (RR = 2.08, Pc < 0.0000056). For DQB1, MMP vs. controls, there was a significantly increased allelic frequency for DQB1*0301 (Pc < 0.00000028) in both males and females; all clinical sites of involvement, with the exception of laryngeal, oesophageal and perianal sites and in patients with detectable circulating anti-BMZ IgG compared with those negative for IgG (P < 0.0096, Pc < 0.019). A positive trend was noted in patients with ocular involvement compared with no ocular involvement and in patients with a clinical score > or = 10 compared with < 10. We found no difference in DQB1*0301 allele frequency between subgroups with or without BP180 or BP230 target antigens. Haplotype frequencies showed an increase in DRB1*04, DQB1*0301 (Pc < 0.000066) and DRB1*11, DQB1*0301 (Pc < 0.000002) among patients compared with controls.

CONCLUSIONS

The DQB1*0301 allele confers a predisposition to all subgroups of MMP and may have a role in T-cell recognition of basement membrane antigens, resulting in the production of anti-BMZ IgG autoantibodies. The positive trend between increased allelic expression of DQB1*0301 in patients with ocular disease and in those with a higher clinical score, further suggests a role for this allele in disease severity.

Autoantibodies to the extracellular and intracellular domain of bullous pemphigoid 180, the putative key autoantigen in bullous pemphigoid, belong predominantly to the IgG1 and IgG4 subclasses

BACKGROUND

Autoantibodies to the extracellular domain (ECD) of bullous pemphigoid (BP) antigen 180 (BP180) are thought to play a crucial part in the pathophysiology of BP.

OBJECTIVES

As the various IgG subclasses have different biological properties, we have sought to assess the relative isotype distribution of IgG to BP180 and their reactivity against the ECD and intracellular domain (ICD) of BP180.

METHODS

The reactivity of 27 sera from patients with BP was assayed by immunoblotting against recombinant proteins covering the ECD and ICD of BP180.

RESULTS

Twenty-seven (100%) and 21 (77%) of 27 BP sera, respectively, contained IgG1 and IgG4 autoantibodies binding to the ECD of BP180. Fourteen (82%) and six (35%) of the 17 BP sera that were reactive with the ICD of BP180 had autoantibodies of the IgG1 and IgG4 subclass, respectively. The profile of the isotype restriction appeared to be similar when the response to the ECD vs. that to the ICD was compared. IgG2 and IgG3 reactivity with BP180 was found less frequently. Patients with BP of longer duration showed a tendency to have, in addition to IgG1, an IgG4 response.

CONCLUSIONS

Consistent with prior evidence indicating that subepidermal blister formation in BP is dependent upon complement activation, the frequent finding of complement-fixing IgG1 autoantibodies to both the ECD and ICD of BP180 might have pathogenic relevance in BP. These findings provide new insights relevant for our understanding of the immune response to BP180, the putative key autoantigen in BP.

Epitopes targeted by bullous pemphigoid T lymphocytes and autoantibodies map to the same sites on the bullous pemphigoid 180 ectodomain

Bullous pemphigoid is a blistering skin disease characterized by autoantibodies directed against the NC16A domain of bullous pemphigoid 180 (collagen XVII), a transmembrane protein of epidermal basal cells. Passive transfer studies in mice have shown that antibodies that bind to this immunodominant region of bullous pemphigoid 180 are capable of inducing a skin disease that closely mimics bullous pemphigoid, supporting the hypothesis that epitopes within NC16A are involved in the pathogenesis of bullous pemphigoid. In this study, we examined the autoimmune T cell response in bullous pemphigoid patients. T cells from eight of 12 bullous pemphigoid patients, all of whom had circulating anti-bullous pemphigoid 180 autoantibodies, showed a specific proliferative response to recombinant forms of NC16A. T cell lines and clones developed from four of these patients recognize the same NC16A peptides as those targeted by autoantibodies from the corresponding individuals. These NC16A-responding T lymphocytes express alpha/beta T cell receptors and CD4 memory T cell surface markers and exhibited a Th1/Th2 mixed cytokine profile that may support the production of antibodies. This new information will aid in defining the key steps involved in the development of the autoimmune response in bullous pemphigoid.

Frequency analysis of autoreactive T-helper 1 and 2 cells in bullous pemphigoid and pemphigus vulgaris by enzyme-linked immunospot assay

BACKGROUND

Bullous pemphigoid (BP) and pemphigus vulgaris (PV) are autoimmune bullous skin diseases mediated by autoantibodies against adhesion molecules of the skin. Previous studies have identified autoreactive T cells in patients with BP and PV, which may be critical in providing B-cell help for autoantibody production.

OBJECTIVES

To evaluate the frequency of autoreactive T-helper (Th) 1 and Th2 cells in patients with BP (n = 7) or PV (n = 1) and in healthy controls (n = 11).

METHODS

In an enzyme-linked immunospot (ELISPOT) assay, microtitre plates were coated with antihuman interleukin (IL)-5 IgG or antihuman interferon (IFN)-gamma IgG prior to culturing human peripheral blood lymphocytes (PBL) with BP180 or desmoglein (Dsg) 3 proteins for 7 days. Cytokine-producing autoreactive T cells were visualized as spot-forming units.

RESULTS

One BP patient with extensive blisters had 5.1 +/- 1.5 (mean +/- SD) BP180-reactive Th1 cells and 2.9 +/- 1.5 Th2 cells per 105 PBL. In contrast, PBL from six BP patients in remission or on immunosuppressive therapy did not form IFN-gamma- or IL-5-producing spots per </= 5 x 105 PBL. The patient with oral PV had 4.7 +/- 2.4 Th1 cells and 3.0 +/- 0.4 Th2 cells per 105 PBL and a vigorous PBL response to Dsg3. In addition, three of 10 controls had BP180-reactive Th1 (2.7-13.8 per 105 PBL) and Th2 (0.3-1.8 per 105 PBL) cells and one control had 9.0 +/- 0.7 Th1 cells and 1.1 +/- 0.8 Th2 cells per 105 PBL, with reactivity to Dsg3. ELISPOT reactivity correlated with 3H-thymidine incorporation in six of seven patients and controls with autoreactive T-cell responses.

CONCLUSIONS

The ELISPOT assay seems to be promising for the quantitative and qualitative analysis of autoreactive T-cell responses in BP and PV.

High levels of interleukin-8, soluble CD4 and soluble CD8 in bullous pemphigoid blister fluid. The relationship between local cytokine production and lesional T-cell activities

BACKGROUND

Bullous pemphigoid (BP) is an inflammatory subepidermal blistering disease associated with autoantibodies that recognize hemidesmosomal proteins. In addition to autoantibodies, the cell-mediated immune reaction is considered to play an important part in blister formation. Objectives To investigate some T-cell activation markers and inflammatory cytokines in the blister fluid and sera of patients with BP.

METHODS

We measured soluble CD4 (sCD4) and soluble CD8 (sCD8), which have been, respectively, associated with CD4 and CD8 T-cell activation. Enzyme-linked immunosorbent assays were also used to quantify the production of the leucocyte chemoattractant interleukin (IL) -8 and of the cytokines IL-1alpha, IL-1beta, IL-6, IL-10 and tumour necrosis factor-alpha in the blister fluid and sera of 11 patients with BP.

RESULTS

The mean +/- SD level of sCD4 in patients' blisters (42.4 +/- 25.0 units mL-1) was significantly elevated (P < 0.005) compared with that in their sera (11.2 +/- 8.9) and that in the suction blisters of 10 healthy people (11.4 +/- 5.4; P < 0.005). Mean +/- SD IL-8 concentrations in BP blisters (4683.6 +/- 3878.1 pg mL-1) were much higher than those in their sera (17.1 +/- 18.9; P < 0.001), and were very significantly elevated (P < 0.005) in comparison with those in suction blisters of healthy persons (512 +/- 292). sCD4 levels in BP blisters were inversely related to IL-10 levels (P = 0. 03, r2 = 0.85), IL-8 levels were positively related to sCD8 levels (P = 0.01, r2 = 0.54), and IL-1beta levels were positively related to sCD8 concentrations (P < 0.005, r2 = 0.65).

CONCLUSIONS

The correlations suggest that there is a delicately orchestrated network of cytokines and cell-mediated immunity operating in BP blisters.

IgG4 and IgE are the major immunoglobulins targeting the NC16A domain of BP180 in Bullous pemphigoid: serum levels of these immunoglobulins reflect disease activity

BACKGROUND

Bullous pemphigoid (BP) is an autoimmune blistering disease associated with autoantibodies against the hemidesmosomal glycoprotein BP180. The noncollagenous (NC)16A domain of BP180 has recently been shown to harbor major antigenic sites recognized by BP sera.

OBJECTIVE

The purpose of this study was to characterize the subclass distribution and fine specificities of autoantibodies to BP180 NC16A present in the circulation of patients with BP before, and during the course of, therapy for this disease.

METHODS

Eighteen BP sera were analyzed by immunoblotting and enzyme-linked immunosorbent assay for the presence of IgG1, IgG2, IgG3, IgG4, and IgE reactive with various sites on the BP180 NC16A domain. The sera were collected before treatment was started and at 4- and 8-week time points after initiation of treatment.

RESULTS

We identified IgG4 and IgE as the major immunoglobulins that preferentially react with two distinct epitopes (MCW-1 and MCW-2) within BP180 NC16A. Levels of these autoantibodies correlated with disease activity in BP. During the course of disease, no change was observed with regard to the immunoglobulin subclass predominantly reacting with BP180 NC16A or the specific epitopes within this domain.

CONCLUSION

Our data demonstrate that remission of BP is paralleled by a decrease of serum levels of IgE and the different IgG subclasses reactive with BP180 NC16A.

IgG autoantibodies from bullous pemphigoid patients recognize multiple antigenic reactive sites located predominantly within the B and C subdomains of the COOH-terminus of BP230

Bullous pemphigoid is a subepidermal bullous disorder characterized by an autoantibody response against the bullous pemphigoid antigen 230 (BP230) and the bullous pemphigoid antigen 180 (BP180), a cytoplasmic component and a transmembrane component, respectively, of hemidesmosomes. Although immunodominant sequences within the extracellular domain of BP180 have been identified, characterization of the antigenic sites on BP230 is still incomplete. To identify autoantibody-reactive sites on BP230 and to examine whether the targeted regions are contained within functionally important domains, recombinant fragments encompassing almost the entire BP230 were used to assess the reactivity of 25 bullous pemphigoid sera by immunoblotting. Our results demonstrate that (i) the region bearing the B and C subdomains of the COOH-terminus of BP230 contains immunodominant sequences recognized by the majority of bullous pemphigoid sera; (ii) additional autoantibody- reactive sites are present over extended regions of the NH2-terminal half of BP230 without evidence for antigenic cross-reactivity between the NH2- and COOH-termini of BP230; and, finally, (iii) autoantibodies reacting with the BP230 tail predominantly belong to the IgG4 and IgG1 subclasses, suggesting that both autoreactive TH2 and autoreactive TH1 cells regulate the autoantibody response to immunodominant sequences of BP230. As the COOH- terminus of BP230 mediates the attachment of keratin intermediate filaments to the hemidesmosomal plaque, whereas its NH2-terminus contains sequences important for its interaction with other constituents of hemidesmosomes, autoantibodies to BP230 might precipitate subepidermal blister formation and perpetuate the disease not only by eliciting an inflammatory reaction but also by interfering with the function of BP230 and thus the stability of hemidesmosomes.

Polymorphisms of HLA-DR and -DQ genes in Japanese patients with bullous pemphigoid

Bullous pemphigoid (BP), an autoimmune skin disease of the elderly, is mediated by autoantibodies that bind to hemidesmosomes of epidermal basal cells. This study investigated BP-associated HLA-DR and -DQ genes among Japanese patients. We analyzed HLA-DR and -DQ genes among 23 Japanese BP patients based on the polymerase chain reaction-restriction fragment length polymorphism. Eighteen of these 23 patients (78%) carried at least one allele of HLA-DRB1*04 or DRB1*1101, with significant increases in HLA-DRB1*04 (*0403, *0406)/DQA1*0301/DQB1*0302 and DRB1*1101/DQA1*0505/DQB1*0302 haplotypes as well as the individual alleles DRB1*1101 and DQB1*0302 (corrected p < 0.05 for each comparison), when compared to control subjects. These data differ from the accepted DQB1*0301 (DQ7) association with the same disease among Caucasians. These findings indicate that different HLA class II haplotypes genetically influence susceptibility to BP among different ethnic groups. Our findings, together with previous reports on Caucasian patients with the pemphigoid group of bullous diseases, suggest that HLA-DRB1 molecules might participate in the regulation of autoimmune responses to BP antigens.

The critical role of IL-12 and the IL-12R beta 2 subunit in the generation of pathogenic autoreactive Th1 cells

Experimental Allergic Encephalomyelitis (EAE) is a demyelinating disease of the central nervous system which is an animal model for the human autoimmune disease, multiple sclerosis. EAE is mediated by CD4+ T cells and the T cells responsible for disease induction produce Th1 cytokines. IL-12 produced by monocytes and dendritic cells is the most critical factor which influences the development and differentiation of pathogenic autoreactive Th1 cells. Here, we review our recent studies on the critical contributions of IL-12 and the IL-12R beta 2 subunit to the generation of autoreactive effector cells which mediate EAE. In addition, we discuss the potential contribution of IL-18 to the upregulation of the IL-12/IL-12R beta 2 pathway and the contribution of the suppressor cytokines, IL-4 and IL-10, in downregulating this pathway. Collectively, our studies demonstrate that the IL-12/IL-12R beta 2 pathway is a critical intermediary in the process of Th1 differentiation which can be both positively or negatively regulated. This pathway remains an attractive immunotherapeutic target for blockade of function with inhibitory reagents or downregulation by Th2 cytokines.

Human CD4+ T lymphocytes with remarkable regulatory functions on dendritic cells and nickel-specific Th1 immune responses

The contribution of T helper (Th) and T cytotoxic (Tc) type 1 lymphocytes in the expression of allergic contact dermatitis to haptens has been amply documented. Conversely, the existence of T cell-based regulatory mechanisms has been poorly investigated. Here, we examined the properties of a subset of nickel-specific CD4+ T cells displaying the cytokine profile (IL-10 , IL-5 , IFN-gamma+/-, IL-4+/-) of T regulatory cells 1 (Tr1) and with the potential to down-modulate immune responses to nickel. Tr1 clones were isolated from skin challenged with NiSO4 and peripheral blood of nickel-allergic patients, and from the blood of healthy individuals. Tr1 clones expressed CD25, CD28, CD30, CD26, and the IL-12 receptor beta2 chain upon activation, whereas the lymphocyte activation antigen-3 was present on 50% of the clones. Monocytes precultured with Tr1 cells in the presence of nickel, or treated with Tr1-derived supernatant, exhibited a markedly diminished capacity to stimulate nickel-specific Th1 responses. Tr1 supernatants also blocked the differentiation of dendritic cells (DC) from monocytes, as well as DC maturation and IL-12 production induced by lipopolysaccharide. As a consequence, the ability of DC to stimulate nickel-specific Th1 and Tc1 responses was greatly impaired. These inhibitory effects were completely prevented by IL-10, but not IL-5, neutralization. In aggregate, the results indicate that Tr1 cells can potently regulate the expression of Th1-mediated allergic diseases via release of IL-10.

Analysis of the T cells that are potentially involved in autoantibody production in pemphigus vulgaris

Pemphigus vulgaris (PV) is a classical example of an antibody-mediated autoimmune disease of the skin. Direct evidence exists that autoantibodies against the desmosomal adhesion molecule, desmoglein 3 (Dsg3), are critical in the pathogenesis of this disease. The transfer of serum IgG antibodies reactive with Dsg3 into newborn mice induces a bullous skin disease resembling PV. Autoreactive T cell responses to Dsg3 may be critical in the pathogenesis of PV because 1) antibody production generally requires T cell help, 2) the involvement of CD4+ T lymphocytes in PV has been suggested by the strong association with distinct HLA class II alleles, and 3) T cell recognition of epitopes of Dsg3 may be crucial for the initiation and perpetuation of the production of Dsg3-specific autoantibodies by B cells. We and others have identified autoreactive T cells recognizing distinct epitopes of the extracellular portion of Dsg3 in PV patients. These autoreactive CD4+ T cells preferentially produced TH2 cytokines such as IL-4, and IL-10. Autoantibodies of the TH2-dependent IgG4 subtype are preferentially seen in active stages of PV disease, while autoantibodies of the TH1-dependent IgG1 subclass are predominant upon remission of PV. Healthy individuals who carried HLA class II alleles similar or identical to those found to be highly prevalent in PV also developed autoreactive T cell responses to Dsg3. Autoreactive T cells from PV patients produced both TH1 and TH2 cytokines; autoreactive T cells from normals produced TH0 cytokines. These observations suggest that Dsg3-specific T cells may provide targets to eventually modulate the T cell-dependent production of pathogenic autoantibodies in PV.

HLA class II restriction of autoreactive T cell responses in pemphigus vulgaris: review of the literature and potential applications for the development of a specific immunotherapy

Pemphigus vulgaris (PV) is a life-threatening autoimmune bullous disease of the skin and mucous membranes which requires immunosuppressive therapy, most commonly a combination of glucocorticoids and additional immunosuppressive agents. Since the side effects of long-term immunosuppressive therapy contribute to the poor prognosis of this disorder, there is considerable interest in a more specific treatment of this severe skin disease. PV may serve as a model disease for the development of a specific immunotherapy, because its pathogenesis as well as involved immunogenetic factors are well-characterized. This review focuses on the characterization of autoreactive T cell responses to desmoglein 3 (Dsg3), the autoantigen of PV, that presumably regulate the production of autoantibodies by providing help to the autoreactive B cells. Current knowledge on T cell epitopes of Dsg3 and the HLA class II alleles that restrict Dsg3-specific autoreactive T cell responses, as well as potential applications for a specific immunotherapy of PV, are described.

IgG autoantibodies from bullous pemphigoid (BP) patients bind antigenic sites on both the extracellular and the intracellular domains of the BP antigen 180

Bullous pemphigoid (BP) and gestational pemphigoid (PG) are subepidermal blistering disorders associated with autoantibodies directed against two components of hemidesmosomes: the BP antigen 180 (BP180) and the BP antigen 230 (BP230). Autoantibodies against the extracellular domain (ECD) of BP180 are thought to play an initiatory role in subepidermal blister formation. To characterize the targeted antigenic sites on BP180, we have assessed the reactivity of sera from BP and PG patients against eukaryotic recombinant proteins encompassing various portions of the ECD and the intracellular domain (ICD) of BP180. Twenty-two of 22 (100%) BP sera that immunoblotted BP180 in keratinocyte extracts, bound a mutant form consisting of the entire ECD of BP180, whereas only three of these 22 sera (14%) reacted against the ECD of BP180 lacking the NC16A membrane proximal region. Thirteen out of the 22 (59%) BP sera recognized the ICD of BP180. Circulating IgG from a representative BP patient that was affinity purified against the ECD of BP180 did not bind the ICD when reblotted, indicating that there was no antigenic cross-reactivity between the ECD and the ICD of BP180. Reactivity against the ICD of BP180 was further ascertained by immunofluorescence microscopy studies showing that nine of the 22 (41%) BP sera stained COS-7 cells expressing the ICD of BP180. Using deletion mutants of the ICD of BP180, the majority of the sera was found to recognize the central region of the ICD of BP180. Specifically, an immunodominant region was localized to an 87-amino acid segment located towards the NH2-terminus of BP180. In contrast to BP sera, five of six (83%) PG sera contained IgG that recognized exclusively the NC16A region, whereas none bound to the ICD of BP180. Together, the results indicate that in BP, autoantibody reactivity to BP180 is not exclusively restricted to the NC16A region, but that additional antigenic determinants exist on the ICD of BP180. The observed heterogeneous immune response against BP180 might reflect intramolecular epitope spreading. Because the ICD ofBP180 harbors functionally important regions, it is possible that autoantibodies against the ICD of BP180 have pathogenic significance for the progression of the disease.