Immunogen sequence: ILKPCSTPSD KLVIDKLVVN FGNVLQEIFT DEARTGQENN LGGEKNGYVT CPFRPDCPLG KSFEELPVSP EIPPRKSQYL R. IL-31 is a T cell cytokine that is preferentially produced by T helper type 2 cells. IL-31 signals through a heterodimeric receptor composed of