#Id: 10302
                                                        #Unit 4. Cell Communication and Cell Signaling
                                                        Positive Costimulatory Receptors: ICOS
ICOS binds to another member of the growing B7 family, ICOS-ligand (ICOS-L), which is also expressed on a subset of activated APCs.
ICOS plays a key role in maintaining the activity of already differentiated effector and memory T cells.