IL13 and immunoglobulin G4-related sclerosing disease: Over-production of TH2-related cytokines (IL-4, IL-13, and IL-5) in IgG4-RD tissues has previously been reported (11) and correlates with IgE and IgG4 class switch, blood eosinophilia, and eosinophilic infiltrates that are common features of IgG4-RD (4, 11).