Activation-induced cytidine deaminase (AID), as a marker of nonspecific immunoglobulin class-switch recombination, was also found to be increased in labial salivary glands of IgG4-RD patients and could contribute to upregulation of IgG4-specific class-switch recombination. Here, AICDA is linked to immunoglobulin G4-related sclerosing disease.