Activates STAT3 and possibly STAT1 and STAT5 through the IL31 heterodimeric receptor composed of IL31RA and OSMR (PubMed:15184896). May function in skin immunity (PubMed:15184896). Enhances myeloid progenitor cell survival in vitro (By similarity). Induces RETNLA and serum amyloid A protein expression in macrophages (By similarity). Detected at low levels in testis, bone marrow, skeletal muscle, kidney, colon, thymus, small intestine and trachea. Up-regulated in skin homing T-cells of patients with atopic dermatitis (AD) and in activated circulating T-cells. Up-regulated in lesional biopsies of patients with allergic contact dermatitis (ACD).