CTLA‐4 co‐receptor impacts on the function of Treg and CD8+ T‐cell subsets

CTLA‐4 has potent regulatory effects on the threshold of T‐cell signalling and, in the process, guards against the development of hyper‐proliferation and autoimmunity. Despite this, the role of CTLA‐4 on specific T‐cell subsets has been unclear. Such studies could shed light on both the function of CTLA‐4, and on the contribution of the subsets to the disease phenotype of the Ctla4^?/? mouse. Recently, a role for this co‐receptor in the function of Treg has been outlined and, in this issue of the European Journal of Immunology, the selective targeting of the T‐box transcription factor Eomes by CTLA‐4 in the regulation of CD8⁺ cytolytic T‐cell (CTL) effector function is shown. Together, these papers shed light on the role of CTLA‐4 in different T‐cell subsets.