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.