T cells compete by cleaving cell surface CD27 and blocking access to CD70‐bearing APCs

T cells compete against each other for access to molecules on APCs in addition to peptide/MHC complexes. However, the identity of cell surface molecules that influence T‐cell competition, other than peptide/MHC, have yet to be defined. Here, we identify CD70, a TNF ligand expressed on activated APCs, as an important mediator of T‐cell competition for APCs. Upon engagement of CD27 by CD70, CD27 is proteolytically cleaved from the surface of the interacting CD8⁺ T cell and captured by CD70 expressing dendritic cells. The capture of CD27 effectively masks CD70 on APCs, disallowing the interaction with CD27 on other competing T cells. Collectively, our data indicate that T cells compete against each other for access to the TNF‐ligand CD70, an interaction that affects the duration and potency of T cell/DC interactions, thus influencing the repertoire of responding CD8⁺ T cells to self or foreign antigens.