A sensitive and specific assay for the serological diagnosis of antilaminin 332 mucous membrane pemphigoid

Background: Antilaminin 332 mucous membrane pemphigoid (MMP) is an autoimmune subepidermal blistering disease with predominant mucosal involvement and autoantibodies against laminin 332. Malignancies have been associated with this disease; however, no standardized detection system for antilaminin 332 serum antibodies is widely available. Objectives: Development of a sensitive and specific assay for the detection of antilaminin 332 antibodies. Methods: An indirect immunofluorescence (IF) assay using recombinant laminin 332 was developed and probed with a large number of antilaminin 332 MMP patient sera (n = 93), as well as sera from patients with antilaminin 332-negative MMP (n = 153), bullous pemphigoid (n = 20), pemphigus vulgaris (n = 20) and noninflammatory dermatoses (n = 22), and healthy blood donors (n = 100). Results: In the novel IF assay, sensitivities with the laminin 332 heterotrimer and the individual α3, β3 and γ2 chains were 77%, 43%, 41% and 13%, respectively, with specificities of 100% for each substrate. The sensitivity for the heterotrimer increased when an anti-IgG4 enriched antitotal IgG conjugate was applied. Antilaminin 332 reactivity paralleled disease activity and was associated with malignancies in 25% of patients with antilaminin 332 MMP. Conclusions: The novel IF-based assay will facilitate the serological diagnosis of antilaminin 332 MMP and may help to identify patients at risk of a malignancy.