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

Antibodies against the extracellular domain of bullous pemphigoid antigen 2 (BPAG2) are thought to play a key role in the pathogenesis of bullous pemphigoid (BP), the most frequent autoimmune bullous disease of the skin. Autoreactive T cell responses to BPAG2 were investigated in 16 BP patients and 24 healthy controls by coculture of PBMC with two recombinant BPAG2 proteins (extracellular domain of BPAG2). Primary in vitro T cell responses to BPAG2 were observed in 10/12 BP patients expressing the BP-associated HLA-DQB1*0301 allele and 8/10 DQB1*0301 positive healthy individuals. DQB1*0301 also restricted three autoreactive T cell lines from two BP patients and a healthy donor. In contrast, PBMC from 14 normal patients carrying HLA class II alleles other than DQB1*0301 were not stimulated by BPAG2. Autoreactive BPAG2-specific CD4(+) T cell lines and clones from five BP patients produced both Th1 and Th2 cytokines, whereas three autoreactive T cell lines from three DQB1*0301 positive normal patients produced exclusively IFN-gamma. The absence of BPAG2-specific Th2 cells in healthy individuals strongly suggests that autoreactive Th2 responses to BPAG2 are restricted to BP patients and may thus be critical in the pathogenesis of BP.

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.

Detection of IgG autoantibodies in the sera of patients with bullous and gestational pemphigoid: ELISA studies utilizing a baculovirus-encoded form of bullous pemphigoid antigen 2.

Autoantibodies against the extracellular domain of bullous pemphigoid antigen 2 (BPAG2) are thought to play a key role in the pathogenesis of bullous pemphigoid and their detection may thus be of diagnostic and prognostic value. The aim of this study was to develop a standardized enzyme-linked immunosorbent assay utilizing the baculovirus-derived protein BV13 (extracellular domain of BPAG2 devoid of 68 amino acids at the C terminus linked to glutathione-S-transferase and 6x His tag) to detect BPAG2-specific autoantibodies. For the enzyme-linked immunosorbent assay, nickel agarose affinity-purified BV13 protein was incubated with sera from patients with bullous pemphigoid (n = 39), gestational pemphigoid (n = 10), and pemphigus vulgaris/pemphigus foliaceus (PV/PF; n = 15), or normal human sera (NHS; n = 18). Nickel affinity-purified proteins from wild-type baculovirus-infected insect cells served as a control. A positive enzyme-linked immunosorbent assay value was defined as reactivity (OD(BV13) - OD(WT)) > mean reactivity + 1 SD of the negative control sera (PV/PF; NHS). Thirty-five of 39 bullous pemphigoid sera and 10 of 10 gestational pemphigoid sera were reactive to BPAG2 compared with none of 15 PV/PF sera and one of 18 NHS (sensitivity, 91.8%; specificity, 97%). Of 16 BPAG2-reactive sera in the enzyme-linked immunosorbent assay, only six were BPAG2-reactive in the western blot, whereas 14 sera immunoprecipitated BPAG2 from extracts of epidermal keratinocytes. The enzyme-linked immunosorbent assay utilizing an eukaryotic BPAG2 protein thus seems to be highly sensitive and specific in the detection of BPAG2-specific antibodies and, hence, may be useful in the diagnosis of bullous autoimmune diseases, such as bullous pemphigoid and gestational pemphigoid.

Immunologic mechanisms in hypersensitivity reactions to metal ions: an overview.

Metal ions such as Ni2+, Co2+, Cu2+, or Cr3+ are haptens with a high immunogenic potential, as contact dermatitis caused by ionic metals occurs in about 10-15% of the human population. Since alloys containing Ni2+, Co2+, and Cr3+ are components of implants in replacement surgery, dentures, orthodontic wires, and various other devices, adverse reactions to metal ions create serious problems in practical medicine as incompatibility reactions to metal-containing biomaterials. On the other hand, contact dermatitis to metal ions such as Ni2+ is a well-established model for studying the molecular mechanisms involved in the recognition of haptens by the immune system. Although many investigations have been performed to elucidate the molecular interactions causing contact hypersensitivity in man, many aspects remain to be clarified. This review will focus on the experimental data accumulated so far on the immunologic mechanisms responsible for the recognition of metal ions by T cells and eliciting adverse immune reactions causing contact dermatitis.

Preferential usage of TCR-Vbeta17 by peripheral and cutaneous T cells in nickel-induced contact dermatitis.

Nickel (Ni) is one of the most common contact sensitizers in man, and Ni-induced contact dermatitis is considered as a model of hapten-induced delayed type hypersensitivity. Previous studies indicated that Ni-reactive T cells derived from Ni-allergic individuals preferentially express distinct TCR-Vbeta chains. However, data on the TCR-Vbeta repertoire of Ni-responsive T cells are not consistent. Therefore, the aim of this study was to identify the TCR-Vbeta receptors of Ni-responsive peripheral and cutaneous T cells in a cohort of 17 donors with Ni-induced contact dermatitis in comparison with those of 6 healthy controls. Peripheral NiSO(4)-responsive T lymphocytes showed a significant overexpression of TCR-Vbeta17 and the frequency of TCR-Vbeta17(+) T cells correlated significantly with the in vitro reactivity of PBMC to NiSO(4). In addition, the cutaneous infiltrate of Ni-induced patch test reactions consisted primarily of Vbeta17(+) T cells. The majority of patch test-derived NiSO(4)-responsive T cells of three allergic donors were TCR-Vbeta17(+), whereas patch test-derived NiSO(4) unresponsive T cells of four additional donors did not express TCR-Vbeta17. Skin-derived Ni-responsive T cell lines from three donors uniformly secreted the Th2 cytokine, IL-5, but no IFN-gamma or IL-10. These in vitro and in vivo findings strongly suggest that T cells with a restricted TCR-Vbeta repertoire, i.e., Vbeta17, predominate in NiSO(4)-induced contact dermatitis and may be crucial in the effector phase of Ni hypersensitivity.

IgG, IgA and IgE autoantibodies against the ectodomain of desmoglein 3 in active pemphigus vulgaris.

BACKGROUND: IgG autoantibodies against desmoglein (Dsg) 3 play a key part in the pathogenesis of pemphigus vulgaris (PV), the most severe autoimmune bullous disorder. OBJECTIVES: To determine whether immunoglobulin isotypes other than IgG are detectable in the sera of patients with PV and whether a particular immunoglobulin subtype is associated with a distinct clinical phenotype of PV. METHODS: Sera from 41 patients with acute-onset, chronic active, and remittent PV disease with mucosal and cutaneous lesions were assayed against a baculovirus-expressed Dsg3 protein by immunoblot analysis. RESULTS: In acute-onset PV, Dsg3-reactive IgG1 was detected in nine of 15 (60%), IgG4 in 14 of 15 (93%), IgA in nine of 15 (60%) and IgE in two of 15 (13%) sera. In chronic active PV, Dsg3-reactive IgG1 was detected in 11 of 18 (61%), IgG4 in 16 of 18 (89%), IgA in 13 of 18 (72%) and IgE in two of 18 (11%) sera. In contrast, sera from patients with remittent PV disease contained only Dsg3-reactive IgG1 in six of eight (75%) and IgG4 in four of eight (50%) cases, but not Dsg3-reactive IgA or IgE. CONCLUSIONS: In extension of previous findings, our study demonstrates that, in addition to IgG autoantibodies, IgA and occasionally IgE autoantibodies reactive with Dsg3 are present in acute and chronic active PV. The detection of Dsg3-reactive autoantibodies of the IgG4, IgA and IgE subclasses in active PV provides additional evidence that PV is a T-helper 2-regulated autoimmune disorder.

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.

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