Fig. 2.

Respective roles of CD28 and ICOS in human Th17 cell function and antitumor activity. The nature of the co-stimulatory molecule signaling determines the functional fate of human Th17 cells. ICOS co-stimulation enhances proliferation and expansion of inflammatory Th17 cells that secrete IFN-γ, IL-17A and IL-17F, while CD28 co-stimulation yields smaller numbers of Th17 cells that appear to be restrained in terms of what molecules they secrete, including less IFN-γ, IL-17A and IL-17F. Importantly, ICOS-stimulated Th17 cells kill human tumors to a greater extent than those stimulated with CD28