The IL-27 p28 subunit alone acts as an antagonist of Th17 activity.
The IL-27 p28 subunit alone can inhibit production of IL-17 by in vitro generated Th-17 cells.
Stumhhofer, J.S., et al. Nature Immunology 10: 937-945 (2006)
Figure (IL-17 vs IFN-g): IL-17 production is inhibited by both IL-27 and p28 – treated, Th17-polarized CD4 cells.