Two Strings in One Bow: PD-1 Negatively Regulates via Co-receptor CD28 on T Cells.

The identity of PD-1 dependency on other receptors and signaling has been unclear. In a recent issue of Science, Hui et al. (2017) and Kamphorst et al. (2017) now show that CD28 expression is a target of PD-1-associated phosphatases and is needed for T cell expansion in anti-PD-1 immunotherapy.