AIP/IgG4-RD was thus shown to be similar to certain forms of systemic lupus erythematosus (SLE), although in AIP/IgG4-RD, but not in SLE, the pathologic pDC response is marked by secretion of IL-33, a cytokine best known for its support of Th2 responses, but more recently shown to support Th1 responses as well (3, 26). Here, IL33 is linked to immunoglobulin G4-related sclerosing disease.