The MH22B2 monoclonal antibody specifically recognizes human Interleukin-22 (IL-22), which is encoded by the IL22 gene. Cross-reactivity of MH22B2 mAb to mouse IL-22 (which shares 79% amino acid identity with human IL-22) has been observed by ELISA and by flow cytometry of HEK293 cells transfected with mouse IL-22 and TH17-differentiated CD4-positive T cells from C57BL/6 mice. IL-22 (with or without other cytokines) is secreted by many T-cell and innate-lymphoid-cell populations. Evidence that IL-22 plays a key role in mucosal immunity includes the restricted expression of the alpha subunit of the heterodimeric IL-22 receptor, called IL-22R1, on epithelial cells and cells of epithelial origin. At epithelial surfaces, IL-22 elicits antimicrobial defenses and maintains epithelial integrity. Alternatively, uncontrolled IL-22 production can result in certain inflammatory disorders. Regulation of IL-22 expression is complex, involving other cytokines (eg, IL-6, IL-23, and TGF-β) and many transcription factors, (eg, AHR, c-Maf, STAT3, RORɤT, BATF, and others).