Identification of target antigen.

<p>(A) The value of cell fluorescence was analyzed by Image J software. *** indicates <i>P</i><0.0001. (B) Five of 20 patients with IgG4-RD presenting relatively higher optical density values on ELISA for HT-29 cell were selected for Western blotting. (C) Western blotting of HT-29 cell extracts with the sera from 5 IgG4-RD patients showed a positive band with a molecular weight of approximately 30 kDa in 3 patients but not in healthy controls. (D) Immunoprecipitation was performed by incubating the extracts of HT-29 with IgG4-RD patient sera and an approximately 30 kDa protein band reacted with antibodies from IgG4-RD patients.