The IL31 gene encodes Interleukin-31, a pleiotropic inflammatory cytokine primarily produced by activated T helper 2 (Th2) cells, but also by mast cells, macrophages, and dendritic cells. It functions by binding to a heterodimeric receptor complex composed of Interleukin-31 receptor alpha (IL-31RA) and Oncostatin M Receptor (OSMR), which are constitutively expressed on various cell types, including epithelial cells, keratinocytes, monocytes, and subsets of neurons in dorsal root ganglia ^[1-2]. This binding activates intracellular signaling pathways such as JAK/STAT, PI3K/AKT, and MAPK, leading to functions in regulating hematopoiesis, immune responses, and the induction of chemokines and pro-inflammatory cytokines ^[1]. IL-31 is strongly associated with pruritic (itchy) skin diseases like atopic dermatitis (eczema), allergic contact dermatitis, prurigo nodularis, and bullous pemphigoid, playing a key role in the sensation of itch ^[3]. It has also been implicated in other conditions such as asthma, allergic rhinitis, inflammatory bowel disease, systemic lupus erythematosus, rheumatoid arthritis, vitiligo, and various cancers (e.g., follicular lymphoma, endometrial cancer, hepatocellular carcinoma) ^[4].

The B6-hIL31 mouse is a humanized model, constructed by replacing the coding sequences of the endogenous mouse Il31 gene with the coding sequences of the human IL31 gene. B6-hIL31 mice can be used for research into the pathogenesis of various inflammatory diseases and cancers. They are also useful for the screening, development, and safety evaluation of IL31-targeted drugs.