ICOS and neoplasm: ICOS mediates tumor progression through T-cell regulation, but this regulatory effect is considered bidirectional; on the one hand, ICOS on Treg cells induces the production of IL-10, mediating immune suppression; on the other hand, ICOS on CD4+ and CD8+ T cells mediates the production of effector molecules such as IFN-γ and TNFα133.