A comparison of the expression of known basement membrane components with the linear IgA disease antigens using the novel substrate cylindroma

Abstract

Linear IgA disease (LAD) is characterized by IgA basement membrane zone autoantibodies. Immunofluorescence, immunoblotting and immunoelectron microscopy studies have established the complexity and heterogeneity of the target antigens. We have studied the expression of the LAD antigens by cylindroma, a benign epithelial tumour that secretes abundant basement membrane, using 57 LAD sera categorized by indirect immunofluorescence on intact and salt-split skin. The expression of known components of hemidesmosomes, the anchoring filaments, extracellular matrix and the anchoring fibrils could be differentiated and were compared with the expression of the LAD antigens. The results showed that the LAD sera bound to the cylindroma tumour in two distinctive patterns. Thirty-three sera were positive on cylindroma. Twenty-seven sera bound to the basement membrane around the tumour clusters and the islets within the clusters in a thin linear band that was occasionally discontinuous. This was similar to the pattern observed with antibodies to the hemidesmosome components, the alpha6beta4 integrin and the bullous pemphigoid antigens BP230 and BP180. This pattern was observed with sera that bound to the epidermal (11) and the dermal (3) aspects of split skin or were negative (11), and with one serum which bound only to intact skin. Seven sera, all binding to the dermal aspect of split skin, bound the tumour cluster basement membrane in a thick band that was identical in appearance to that seen with antibodies to collagen VII; however, binding to the islets was either identical to collagen VII or similar but differentiated with double staining. Some sera were negative on cylindroma. Using fluorescence overlay antigen mapping we demonstrated colocalization of some epidermal-associated LAD target antigens with known hemidesmosome proteins, and colocalization of some dermal-associated LAD target antigens with anchoring fibril components. The results using cylindroma as substrate suggest that LAD autoantibodies may react with three or more target antigens. We propose from the results of this study that the autoantibodies in LAD target multiple antigens associated with hemidesmosomes and anchoring fibrils.

Vancomycin-induced linear IgA disease with autoantibodies to BP180 and LAD285.

“…A similar picture of heterogeneous target antigens has been found in idiopathic LAD; 28 investigators have identified BP180 29–31 and its extracellular domain (LAD1; 97 kDa/120 kDa), 26,30–33 BP230, 29–31,34 collagen VII, 30,31 , 35–37 antigens of molecular weight 285 kDa, 16,30 , 31 280 kDa 38 (possibly the same as the 285 kDa antigen), 200 kDa, 30,31 , 38 160/170 kDa, 140 kDa and other antigens of < 100 kDa, 30 as targets. Some patients with idiopathic LAD have multiple target antigens, but previously this has not been reported in drug‐induced LAD.…”

The lupus band: do the autoantibodies target collagen VII?

“…Twenty‐six patients who satisfied the 1982 American Rheumatism Association criteria 4 for SLE were recruited from the Connective Tissue Diseases Clinic, John Radcliffe Hospital. After informed consent, nonlesional skin biopsies were taken from the medial aspect of the forearm for the lupus band test (LBT) using a standard direct immunofluorescence technique, 5 to study expression of the main components of the skin BMZ in nonlesional SLE skin by an indirect immunofluorescence microscopy method 6 before the colocalization study. The following well‐characterized monoclonal antibodies (Table 1) were used for immunolabelling of the different parts of the BMZ: LH7.2 directed against the NC1 domain of collagen type VII, anticollagen IV, GB3 to the γ‐chain of laminin‐5, G71 to β 4 ‐integrin, antifibronectin, antilaminin‐1, and 10E4 to heparan sulphate proteoglycans.…”

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

“…Our own studies using cylindroma tissue as a substrate have suggested that LAD autoantibodies may react with four major antigens, two epidermal and two dermal 31 . A preliminary IB study on 63 LAD sera showed that up to nine target antigens were recognized by IgA autoantibodies in epidermal and dermal tissue extracts, including BP230, BP180, collagen VII, the uncharacterized LAD285, and other less well recognized antigens 7 .…”