Despite a remarkable degree of plasticity, stochasticity and functional heterogeneity in their individual response, T cell overall response to infection is consistent and robust. This implies a coordinated response across a system-wide level to facilitate the control of pathogens while maintaining self-tolerance. Much research has focused on individual T cell activation and differentiation, but how the stochastic individual responses are integrated is unknown. This global coordination can only be achieved by constant cellular communication between responding cells and has to be supported by the ecosystem they reside in. In this presentation, I will focus on the impact of CD8 T cell communication through the cytokine IFNg. I will present data supporting the existence of IFNg driven T cell communication during infection, and its relevance for T cell response. I will then move on to situation where IFNg production is chronic, namely during immune response to tumours, and present data demonstrating that chronic IFNg signalling in T cells restricts their anti-tumour response by inhibiting stem-like T cell maintenance.