Circulating IgA and IgE autoantibodies in antilaminin‐332 mucous membrane pemphigoid

Background Antilaminin‐332 mucous membrane pemphigoid (MMP) is a chronic autoimmune bullous disease that is often associated with internal malignancy. IgG autoantibodies against laminin‐332 in patients with MMP are well documented; however, IgA and IgE autoantibodies against laminin‐332 have not yet been described. Objectives To characterize IgA and IgE autoantibodies binding to laminin‐332 in sera from patients with antilaminin‐332 MMP. Methods Sera and skin samples from four patients who met the following criteria were used: (i) subepidermal blistering lesions present on the mucous membranes; (ii) in vivo deposition of IgG along the epidermal basement membrane zone of sampled skin; (iii) circulating IgG antibasement membrane zone antibodies that react with the dermal side of salt‐split normal human skin; and (iv) circulating IgG autoantibodies that do not show positivity against type VII collagen or 200‐kDa protein (p200 antigen) in immunoblot analysis using dermal extracts. Circulating IgG/IgA/IgE class autoantibodies against laminin‐332 were determined by immunoblotting. Results Circulating IgG autoantibodies against the γ2, α3/γ2, α3 and α3/β3/γ2 subunits of laminin‐332 were demonstrated in sera from four patients, respectively. Serum from one of the four patients showed IgA reactivity with the α3/β3/γ2 subunits of laminin‐332. Serum from one of the four patients showed IgE reactivity with the γ2 subunit of laminin‐332. The control sera failed to display IgG/IgA/IgE reactivity to laminin‐332. Conclusions In addition to IgG autoantibodies, circulating IgA and IgE autoantibodies against laminin‐332 are detectable in a subset of patients with antilaminin‐332 MMP.