Disclosed is the use of an agonist or antagonist of IL-33 for the manufacture of a medicament for modulating an immune disorder or condition, wherein: a) the agonist of IL-33 is IL-33 or a nucleic acid encoding IL-33 and b) the antagonist of IL-33 is an antibody that specifically binds to IL-33 (or antigen binding fragment thereof), an siRNA to IL-33, or antisense nucleic acid to IL-33.