Lymph nodes fuel KLF2-dependent effector CD8 T cell differentiation during chronic infection and checkpoint blockade.

Exhausted CD8 T (T) cell responses are maintained by precursors of exhausted T (T) cells that possess high self-renewal and developmental potential. T cells also drive the proliferative burst of effector T cells upon therapeutic immune checkpoint blockade (ICB). However, the spatial context and signals that regulate their differentiation and function are not well defined. Here we identify developmental and functional compartmentalization of T and T cells across secondary lymphoid organs during chronic infection. We show that stem-like CD62L T and effector-like CX3CR1 T cells constitute a distinct developmental lineage that is promoted by the lymph node (LN) microenvironment and dependent on the transcription factor KLF2. LNs act as a niche in which migratory dendritic cells provide antigen and costimulatory signals to maintain the proliferative fitness of CD62L T cells and generation of CX3CR1 T cells. Moreover, LNs exclusively drive the proliferative burst and systemic dissemination of CX3CR1 T cells during ICB. Thus, our findings identify a unique role for LNs in the maintenance of T cell differentiation and function during systemic chronic infection and ICB therapy.