Epiligrin, the major human keratinocyte integrin ligand, is a target in both an acquired autoimmune and an inherited subepidermal blistering skin disease.

Epiligrin, the major component of human keratinocyte extracellular matrix, serves as the preferred integrin ligand for alpha 3 beta 1 in plasma membranes and focal adhesions, and colocalizes with alpha 6 beta 4 in hemidesmosomes. In human skin, epiligrin is found in the lamina lucida subregion of epidermal basement membrane, where it is thought to be associated with anchoring filaments. We have identified three patients with an acquired mucosal predominant subepidermal blistering disease who have IgG anti-basement membrane autoantibodies that bind the lamina lucida/lamina densa interface of epidermal basement membrane, stain cultured human keratinocyte extracellular matrix, and immunoprecipitate disulfide linked polypeptides of 170, 145, 125, and 95 kD in human keratinocyte culture media in a pattern identical to that of P1E1, a murine monoclonal antiepiligrin antibody. Comparative immunoprecipitation studies of patient sera, P1E1, and GB3 monoclonal antibody show that epiligrin is identical to the antigen (i.e., BM600 or GB3 antigen) previously reported to be absent from the skin of patients with lethal junctional epidermolysis bullosa, an inherited subepidermal blistering disease. Moreover, skin from a fetus with this disease shows no evidence of reactivity to patient antiepiligrin autoantibodies or P1E1. These studies show that antiepiligrin autoantibodies are a specific marker for a novel autoimmune blistering disease and that the epidermal basement membrane antigen absent in patients with lethal junctional epidermolysis bullosa is epiligrin.

Human keratinocytes and A-431 cells synthesize and secrete factor B, the major zymogen protease of the alternative complement pathway.

Biosynthetic radiolabeling studies demonstrate that human keratinocytes and A-431 cells, a human epidermoid carcinoma cell line, synthesize and secrete factor B as a monomeric 105-kD protein. Epithelial cell-derived factor B comigrates in SDS-PAGE with that produced by HepG2 cells, a human hepatoma cell line traditionally employed in studies of complement component biosynthesis. Comparative pulse-chase studies in A-431 and HepG2 cells show that this alternative pathway complement component is produced as co-migrating 100-kD intracellular proteins that are processed in both cell types to 105-kD extracellular factor B. Quantitatively, immunoprecipitable factor B accounts for 0.05% of radiolabeled proteins in A-431 cell culture media. Treatment of biosynthetically radiolabeled A-431 cell culture media with cobra venom factor and factor D for 60 min at 37 degrees C produces the specific factor B cleavage products Ba and Bb. These fragments are not identifiable in control culture media subjected to similar treatment in the absence of alternative pathway activators. Northern blot analysis of total cellular RNA from human keratinocytes, A-431 cells, and HepG2 cells reveals qualitative identity of a 2.8-kb factor B mRNA species in these three cell types. The relative level of factor B mRNA expression in these cells parallels their level of factor B protein synthesis (i.e., HepG2 cells greater than A-431 cells greater than human keratinocytes). Epithelial cell-derived factor B may play an important role in local inflammatory reactions and also directly interact with epithelial cell derived C3--a key classical and alternative pathway complement component recently shown to be produced by human keratinocytes.

Autoantibodies from patients with cicatricial pemphigoid target different sites in epidermal basement membrane.

Indirect immunogold electron microscopy studies of cryofixed, freeze-substituted, and post-embedded normal human skin were performed to localize precisely the ultrastructural binding site of circulating autoantibodies from two groups of patients with cicatricial pemphigoid. One group of patients had circulating IgG autoantibodies that bound the dermal side of 1 M NaCl-split skin and immunoprecipitated epiligrin. The other group of patients had circulating IgG autoantibodies directed against the epidermal side of 1 M NaCl-split skin and showed no specific reactivity to any keratinocyte polypeptide by immunoprecipitation. IgG autoantibodies from all patients with anti-epiligrin cicatricial pemphigoid bound the lowermost aspect of the lamina lucida at its interface with the lamina densa; the greatest staining was seen beneath and beside hemidesmosomes. In contrast, IgG from cicatricial pemphigoid patients whose autoantibodies bound the epidermal side of 1 M NaCl-split skin localized to hemidesmosomes and the junction between hemidesmosomes and the plasma membranes of basal keratinocytes. Although the latter staining pattern is similar to that observed with anti-BPAG2 autoantibodies, sera from our patients with cicatricial pemphigoid did not bind BPAG2 in immunoprecipitation studies of radiolabeled human keratinocyte extracts or show immunoblot reactivity to a fusion protein corresponding to the immunodominant epitope of this polypeptide. These studies demonstrate the following: 1) Autoantibodies from patients with anti-epiligrin cicatricial pemphigoid consistently bind the lower lamina lucida at its interface with the lamina densa; and 2) other patients with the same phenotype may have IgG autoantibodies against yet-unknown epitopes in basal keratinocytes.

A bullous skin disease patient with autoantibodies against separate epitopes in 1 mol/L sodium chloride split skin.

BACKGROUND: We describe a patient with a subepidermal bullous skin disease associated with autoantibodies recognizing separate epitopes in 1 mol/L sodium chloride (NaCl) split skin. OBSERVATIONS: Direct immunofluorescence microscopy showed deposits of immunoglobulins and C3 in a continuous pattern in the patient's epidermal basement membrane zone. Direct immunoelectron microscopy demonstrated thick deposits of IgG overlying the lamina lucida and the lamina densa in a unique pattern. The patient had circulating IgG anti-basement membrane zone antibodies that bound both sides of 1 mol/L NaCl split skin, exhibited at least a fourfold-higher titer against the dermal side of this test substrate, and bound basal keratinocyte hemidesmosomes as well as focal sites along the superior portion of the lamina densa on indirect immunoelectron microscopy. Affinity purification of anti-basement membrane zone antibodies against epidermal or dermal strips of 1 mol/L NaCl split skin yielded IgG that only bound the side of split skin from which it was eluted. The patient's serum contained IgG that immunoprecipitated and immunoblotted the 230- and 170-kd bullous pemphigoid antigens. Affinity purification of patient antibody against bullous pemphigoid antigen immobilized on nitrocellulose paper yielded IgG that bound only the epidermal side of 1 mol/L NaCl split skin. The patient showed no evidence of reactivity against type VII collagen by direct immunoelectron microscopy, indirect immunoelectron microscopy, or immunoblot. CONCLUSIONS: This patient's bullous skin disease is associated with IgG anti-basement membrane zone antibodies with two specificities: one recognizing the bullous pemphigoid antigen in the epidermal side of 1 mol/L NaCl split skin, and another binding a distinct, yet presently unidentified, epitope in the superior aspect of the lamina densa.

Autoantibodies from patients with localized and generalized bullous pemphigoid immunoprecipitate the same 230-kd keratinocyte antigen.

Two patients demonstrating the typical clinical, histologic, and immunopathologic features of nonscarring localized bullous pemphigoid are described. These patients possess circulating IgG autoantibodies that bind the epidermal side of 1.0-mol/L sodium chloride-split human skin in indirect immunofluorescence microscopy. Immunnoprecipitation studies demonstrate that these patients have circulating autoantibodies that immunoprecipitate the same 230-kd bullous pemphigoid antigen that is precipitated by autoantibodies from patients with generalized bullous pemphigoid. These findings indicate that localized bullous pemphigoid is a true clinical variant of generalized pemphigoid rather than a separate nosologic entity.

Waldenström macroglobulinemia with an IgM-kappa antiepidermal basement membrane zone antibody.

BACKGROUND: Waldenström macroglobulinemia, a lymphoplasmacytoid cell malignant neoplasm associated with a monoclonal IgM paraprotein, has been associated with a number of cutaneous manifestations. On rare occasions, IgM deposits have been demonstrated in the epidermal basement zone of patients with WM. OBSERVATIONS: We report the case of a patient with Waldenström macroglobulinemia and IgM-kappa paraprotein who had development of an eruption of pruritic papules and demonstrated the following unusual immunopathologic findings: (1) deposits of IgM-kappa in the epidermal basement membrane zone of lesional and nonlesional skin; (2) a circulating IgM-kappa antiepidermal basement membrane zone antibody; and (3) binding of this circulating IgM-kappa antiepidermal basement membrane zone antibody to both sides of 1 mol/L sodium chloride split skin. The cutaneous eruption cleared completely with oral psoralen with long-wave UV radiation in the A range (PUVA) therapy. CONCLUSIONS: We present a patient with Waldenström macroglobulinemia who had a distinctive papular eruption and immunopathologic findings suggesting that his paraprotein has specificity for the epidermal basement membrane zone.

Childhood localized vulvar pemphigoid is a true variant of bullous pemphigoid.

BACKGROUND: Childhood localized vulvar pemphigoid has been recently reported in four girls. A fifth child with this proposed rare variant of bullous pemphigoid is described. Moreover, findings in the various immunopathologic studies we performed establish this entity as a true morphologic variant of bullous pemphigoid. OBSERVATIONS: In situ deposits of IgG in this patient's epidermal basement membrane zone localized to the epidermal side of 1 mol/L of saline-split skin. Moreover, the patient had circulating IgG autoantibodies that bound the epidermal side of 1 mol/L of saline-split skin in indirect immunofluorescence microscopy and immunoprecipitated the 230-kd bullous pemphigoid antigen from biosynthetically radiolabeled human keratinocyte extracts. These laboratory findings are identical to those documented in patients with the generalized "classic" form of bullous pemphigoid. CONCLUSIONS: This study demonstrates that a child with clinical, histopathologic, and immunopathologic features of localized vulvar pemphigoid had circulating autoantibodies that identify a specific keratinocyte antigen, the bullous pemphigoid antigen, which may serve as a molecular marker for this disease.

Antiepiligrin cicatricial pemphigoid. A subepithelial bullous disorder.

BACKGROUND: Epiligrin is a glycoprotein complex deposited in extracellular matrix by cultured human keratinocytes that serves as the major integrin ligand of these cells. In human skin, epiligrin is found at the interface of the lamina lucida and lamina densa in epidermal basement membrane where it is believed to be associated with anchoring filaments and plays an important role in keratinocyte adhesion. METHODS AND RESULTS: We have identified six patients with a subepithelial bullous disorder of mucous membranes and skin who have IgG anti-basement membrane autoantibodies that immunoprecipitate epiligrin from human keratinocyte extracts and culture media. These patients' IgG autoantibodies also bind epiligrin in human keratinocyte extracellular matrix and epidermal basement membrane as determined by immunofluorescence and immunoelectron microscopy. Studies of 10 patients who are clinically indistinguishable from subjects with anti-epiligrin autoantibodies (ie, cicatricial pemphigoid patients) found that while seven had anti-basement membrane autoantibodies, the latter are directed exclusively against a region of epidermal basement membrane that does not contain epiligrin, are present in low titer (ie, < or = 1:10), do not react with keratinocyte extracellular matrix, and do not bind epiligrin (or any other specific antigen) in immunoprecipitation studies of human keratinocyte extracts or media. Antiepiligrin autoantibodies were also not detected in studies of 36 additional patients with bullous diseases or six normal volunteers. CONCLUSIONS: Cicatricial pemphigoid is a disease phenotype in which patients' autoantibodies may target different constituents of epidermal basement membrane. Antiepiligrin autoantibodies are a specific immunologic marker for a group of patients with a disease entity that we propose to designate antiepiligrin cicatricial pemphigoid.

Epiligrin is decreased in papulonodular basal cell carcinoma tumor nest basement membranes and the extracellular matrix of transformed human epithelial cells.

Patients with anti-epiligrin cicatricial pemphigoid have anti-basement membrane autoantibodies that immunoprecipitate a set of disulfide-linked human keratinocyte polypeptides that co-migrate in sodium dodecyl sulfate polyacrylamide gel electrophoresis with the same complex identified by monoclonal anti-epiligrin (P1E1) and monoclonal anti-nicein/kalinin (GB3) antibodies. In an attempt to further compare the reactivity of patient autoantibodies, P1E1 and GB3, these reagents were tested against the tumor nest basement membranes of 7 papulonodular basal cell carcinomas. These studies found that all of these reagents showed markedly decreased or no reactivity against this substrate. Though their concordant lack of reactivity failed to distinguish these antibodies, these studies did identify a significant defect in papulonodular basal cell carcinoma tumor nest basement membranes. Similarly, integrin subunits alpha 6, beta 4, alpha 3, and alpha 2 as well as bullous pemphigoid antigens 1 and 2 (all potential receptors for the extracellular matrix ligands epiligrin and nicein/kalinin) were also reduced in these tumor nest basement membranes. These findings signify an extensive impairment in the lamina lucida of this neoplasm's basement membrane. Related comparative studies of normal human keratinocytes and transformed human epithelial cell lines (specifically, A-431 and HaCat cells) showed that epiligrin production is markedly decreased in the latter. Decreased expression of epiligrin and nicein/kalinin in papulonodular basal cell carcinoma tumor nest basement membranes in vivo and transformed epithelial cells in vitro indicate that this complex is a transformation-sensitive cell adhesion ligand.

Direct immunofluorescence microscopy of 1 mol/L sodium chloride-treated patient skin.

Patients with bullous pemphigoid and those with epidermolysis bullosa acquisita often demonstrate virtually identical clinical, histologic, and immunopathologic features. Although some patients can be distinguished by their pattern of circulating IgG anti-basement membrane zone antibody binding to 1 mol/L sodium chloride-split human skin, approximately 20% and 50% of bullous pemphigoid and epidermolysis bullosa acquisita patients, respectively, do not possess such antibodies. Hence this study sought to determine whether these patients can be distinguished by mapping the distribution of basement membrane zone immunoreactants in patient skin split in vitro by 1 mol/L sodium chloride. All sodium chloride-treated samples from patients with bullous pemphigoid (n = 8), epidermolysis bullosa acquisita (n = 4), or other bullous skin diseases (n = 6) contained a lamina lucida cleavage plane bounded by bullous pemphigoid antigen and laminin; moreover, treatment of patient samples was performed without loss of tissue substrate or in situ immunoreactants. Deposits of IgG were found on the epidermal side of sodium chloride-treated skin from 13 of 14 bullous pemphigoid samples; IgG deposits in bullous pemphigoid samples were exclusively epidermal in eight, epidermal and dermal in five, and solely dermal in one. In contrast, IgG was found exclusively on the dermal side of sodium chloride-treated samples from patients with epidermolysis bullosa acquisita. Although IgG mapping distinguished bullous pemphigoid and epidermolysis bullosa acquisita patients in 94% of these samples, the distribution of C3 in sodium chloride-treated patient skin was more variable and less predictive diagnostically.(ABSTRACT TRUNCATED AT 250 WORDS)