IL31, also known as interleukin 31, is a member of the gp130/interleukin-6 cytokine family that is produced by cell types such as T helper 2 lymphocytes and cutaneous lymphocyte antigen positive skin homing T cells. IL-31 signals via a heterodimeric receptor complex composed of a gp130 related molecule termed IL-31RA (also GPL and GLMR) and an Oncostatin M receptor (OSM R?). The IL-31 receptor is constitutively expressed by keratinocytes and upregulated by IFN? on monocytes. Recombinant canine IL31, fused to His-tag at C-terminus, was expressed in insect cell and purified by using conventional chromatography techniques.