Human autoantibodies against a desmosomal protein complex with a calcium-sensitive epitope are characteristic of pemphigus foliaceus patients.

Pemphigus foliaceus (PF) patients have antibodies against a tightly, but noncovalently bound complex of polypeptides, which consists of desmoglein I (DGI) and other, possibly desmosomal, proteins. Most PF antibodies bind a calcium-sensitive epitope on this complex and chelation of calcium destroys the reactivity of these sera with the complex, but not the complex itself. The PF sera that do bind the desmosomal complex in the absence of calcium are those sera capable of binding denatured DGI on immunoblotting, and these same sera also immunoprecipitate only DGI when the desmosomal complex is dissociated with SDS. These findings demonstrate that autoantibodies against a complex of desmosome-associated proteins are characteristic of PF and define a calcium-sensitive conformational epitope on this complex.

Identification of pemphigus vulgaris antigen extracted from normal human epidermis and comparison with pemphigus foliaceus antigen.

Immunoprecipitations of cultured keratinocyte extracts have shown that pemphigus vulgaris (PV) sera bind a polypeptide of 210,000 mol wt with disulfide-linked chains of 130,000 and 85,000 mol wt. To identify proteins in normal human skin recognized by PV antibodies, we performed immunoprecipitations of normal human epidermal extracts. All 22 PV sera tested immunoprecipitated a complex of polypeptides (PV complex) of 210,000, 130,000, and 85,000 mol wt, after reduction. One- and two-dimensional gel electrophoresis showed that the 130,000- and 85,000-mol-wt polypeptides of the PV antigen from both cultured keratinocytes and epidermis have identical charges and sizes. In addition to precipitating the PV complex, 14 of 22 PV sera also have antibodies to a calcium-sensitive epitope on a different complex of polypeptides (PF complex) which has previously been shown to be precipitated by all pemphigus foliaceus (PF) sera. The PF complex consists of polypeptides of 260,000, 160,000, 110,000, and 85,000 mol wt. Although the majority of PV sera also precipitate the PF complex, no PF sera precipitate the PV complex. Thus, PV and PF can be absolutely distinguished on a molecular level using the patients' autoantibodies. The PV and PF complexes, although distinct, have certain similarities. The 85,000-mol-wt polypeptide of each is identical. The 160,000-mol wt-peptide of the PF complex and the 130,000-mol-wt peptide of the PV complex have the same isoelectric point and both are capable of disulfide linkage to the 85,000-mol-wt polypeptide. The PV and PF complexes are closely related and may prove important in cell adhesion.

IgA immune complexes in patients with dermatitis herpetiformis occur in the absence of IgA rheumatoid factor.

Thirty to forty percent of patients with dermatitis herpetiformis (DH) have IgA-containing circulating immune complexes (IgA-CIC); however, the antigenic composition of these complexes as well as the role they play in the pathogenesis of DH are unknown. The failure to detect wheat protein in these IgA-CIC, despite the association of DH with gluten-sensitive enteropathy, suggests that the IgA-CIC in DH may be similar to those seen in the IgA nephropathies and represent IgA rheumatoid factor (RF)-IgG complexes. We have examined the sera of 32 patients with DH, 16 non-DH patients positive for RF by latex fixation, and 15 normal subjects for IgA and IgM RF using enzyme-linked immunosorbent assays (ELISAs) and for IgA-CIC using an anti-C3 ELISA. Thirteen of 16 (81%) latex fixation test-positive patients had IgA RF by ELISA and 15/16 (94%) had IgM RF by ELISA. The total amount of RF detected by the ELISA (IgA + IgM RF) correlated with the latex fixation titer (r = 0.678, p = 0.004) in these latex fixation-positive patients. Six of the 16 (38%) latex fixation-positive patients also were found to have IgA-CIC. Solid phase absorption using goat antihuman C3 decreased the levels of immune complexes but not the level of IgA RF, suggesting the IgA-CIC detected do not represent uncomplexed IgA RF. In contrast, although 12 of 31 (39%) patients with DH had IgA-CIC ranging in amount from 0.331-26.0 micrograms IgA/ml (nl less than 0.150 microgram IgA/ml), only 1 of 32 (3%) DH patients had detectable levels of IgA RF (7.0 micrograms IgA/ml, nl less than 2.0 micrograms IgA/ml). Low levels of IgM RF were found in 8/32 (25%) of patients with DH (1.1-1.6 micrograms IgM/ml, nl less than 1.0 microgram IgM/ml). These data document that IgA RF is not present in the sera of patients with DH independent of the presence or absence of IgA-CIC and that it is unlikely that the IgA-CIC present are IgA RF complexed with autologous IgG.

Drug-induced pemphigus: autoantibodies directed against the pemphigus antigen complexes are present in penicillamine and captopril-induced pemphigus.

Pemphigus is an autoimmune blistering disease characterized by circulating autoantibodies directed against the keratinocyte cell surface. The two variants, pemphigus foliaceus and pemphigus vulgaris, can be distinguished at the molecular level by immunochemical studies. The large majority of patients with pemphigus develop the disease spontaneously; however, there is a small group of patients who develop pemphigus after treatment with certain medications, of which penicillamine and captopril are the best documented. Most patients with drug-induced pemphigus have circulating and/or tissue bound epidermal cell surface autoantibodies; however, the molecular specificity of these autoantibodies has not been studied. We performed immunoprecipitation studies utilizing extracts of 125I-labeled suction blister epidermis and the sera of three patients with drug-induced pemphigus foliaceus (two due to penicillamine and one due to captopril) and one patient with captopril-induced pemphigus vulgaris. We found that the three patients with drug-induced pemphigus foliaceus had circulating autoantibodies that are directed against the pemphigus foliaceus antigen complex and that the one patient with drug-induced pemphigus vulgaris had circulating autoantibodies that are directed against the pemphigus vulgaris antigen complex. This study demonstrates that autoantibodies from drug-induced pemphigus patients have the same antigenic specificity, on a molecular level, as do autoantibodies from other pemphigus patients.

Biochemical differentiation of types of pemphigus.

There are two major types of pemphigus as determined by clinical and histologic criteria: PV, in which the blister forms at the suprabasilar layer of the epidermis, and PF, in which the blister forms in the more superficial epidermis. The autoantibodies from both types of pemphigus bind in an identical fashion to the cell surface of keratinocytes. Blocking studies suggest that PF and PV sera recognize different epidermal antigens. Absorption studies have suggested that a variety of antigens react with pemphigus autoantibodies, but the conditions of these studies may have absorbed or inactivated the antibodies nonspecifically. By immunoblotting it has been shown that a subset of PF and FS patients' sera bind to a 160-kD glycoprotein that is identical to DG I, a desmosomal core glycoprotein. Also by immunoblotting, a few PV sera recognize a 33-kD protein from human epidermis and a 140-kD protein from bovine tongue. All PV sera tested by immunoprecipitation bind to a 210-kD glycoprotein that is synthesized by cultured human keratinocytes. This glycoprotein consists of two disulfide-linked polypeptides of 130 and 80 kD. PF sera do not recognize these polypeptides. Thus, even though the antigen specificities at a molecular level of all PF and PV sera are not fully known, it is clear that PV and PF autoantibodies bind different molecules. These findings of disease specific antigens may account for the different clinical forms of these diseases.

Response to injury of skin involved and uninvolved with psoriasis, and its relation to disease activity: Koebner and 'reverse' Koebner reactions.

We studied the response to a standard skin injury in the involved and uninvolved skin of twenty-four subjects with psoriasis to determine whether a relationship exists between disease activity and the Koebner reaction. We found that 25% of patients had a positive Koebner reaction and 67% had a positive 'reverse' Koebner reaction (psoriasis clearing following skin injury). If psoriasis occurred in one area of injury, all injured areas developed psoriasis, and 'all-or-none' phenomenon. If psoriasis cleared from the traumatized area, no psoriasis occurred in the uninvolved sites. The 'reverse' Koebner reaction and the Koebner reaction are thus mutually exclusive. Disease activity, by our criteria, did not predict a positive Koebner reaction, but a positive Koebner reaction did predict subsequent disease activity. These observations suggest that humoral factors govern the development of clearing or psoriasis after a standard injury.

Demonstration of an adhering-junction molecule (plakoglobin) in the autoantigens of pemphigus foliaceus and pemphigus vulgaris.

Pemphigus foliaceus and pemphigus vulgaris are skin diseases in which antibodies against the cell surface of keratinocytes destroy the adhesion between epidermal cells, producing blisters. Patients with pemphigus foliaceus have antibodies to a complex of three polypeptides of 260, 160, and 85 kd (the foliaceus complex), whereas patients with pemphigus vulgaris have antibodies to a complex of 210-kd, 130-kd, and 85-kd polypeptides (the vulgaris complex). The 160-kd polypeptide of the foliaceus complex has been identified as desmoglein, a desmosomal glycoprotein. We suspected that the 85-kd component in both these antigenic complexes might be plakoglobin, another molecule in the adhering junctions of cells. To characterize these antigenic complexes, we used the serum of five patients with pemphigus foliaceus, that of four patients with pemphigus vulgaris, and monoclonal antiplakoglobin antibodies. We found that monoclonal antibodies to plakoglobin immunoprecipitated the 85-kd polypeptide from the dissociated foliaceus and vulgaris complexes and precipitated both complexes from epidermal extracts. Serum from patients with pemphigus foliaceus or pemphigus vulgaris (but not from four normal controls) bound desmoglein and the 130-kd polypeptide, respectively, showing that these peptides (and not plakoglobin) are the antigenic binding sites in these disorders. We conclude that plakoglobin, a protein of the adhering junctions of epidermal cells, is the 85-kd molecule in the antigenic complexes found in both pemphigus foliaceus and pemphigus vulgaris, although it is not the binding site in either disorder.