Improvement of immunological tests for detecting autoantibodies in patients with lamina lucida-type linear IgA bullous dermatosis

Background: In the diagnosis of linear IgA bullous dermatosis (LABD), detection of IgA at the epidermal basement membrane zone and circulating IgA autoantibodies are essential. The disease has two subtypes, lamina lucida-type and sublamina densa-type, with 120 kDa LAD-1 and 97 kDa LABD97 as major autoantigens for lamina lucida-type. Normal human epidermal keratinocytes (NHEK) and HaCaT cells are widely used for immunoblotting (IB) in the diagnosis process, but they do not provide high sensitivity and semiquantitative analysis.

Objective: To develop a more sensitive and convenient method for detecting IgA antibodies in lamina lucida-type LABD patients.

Methods: The expressions of LAD-1 and LABD97 in lysates and culture supernatants from Ker-CT, HaCaT, DJM-1, and NHEK were compared. The sensitivity of IBs using concentrated culture supernatants of HaCaT and Ker-CT and ELISAs using several recombinant proteins (RPs) corresponding to BP180 ectodomain were compared using 55 sera from LABD patients.

Results: In culture supernatant, Ker-CT expressed higher amounts of LAD-1 and LABD97. IBs using concentrated culture supernatant of HaCaT and Ker-CT showed 43 % and 46 % positivity to sera from LABD patients, respectively. In ELISAs, the RP of amino acids 490-1421 of BP180 showed the highest positivity (80.0 %) among several proteins. Additionally, this ELISA showed reduced OD values in LABD and related diseases patients' sera at remission.

Conclusion: The ELISA using the RP coding amino acids 490-1421 of BP180 is useful for identifying IgA antibodies and monitoring disease activity in lamina lucida-type LABD patients.