In the abstract for their most recent paper, published in the October 17th issue of Nature Communications, the Farber lab submits that human T cells coordinate adaptive immunity in diverse anatomic compartments through production of cytokines and effector molecules, but it is unclear how tissue site influences T cell persistence and function. They used single cell RNA-sequencing (scRNA-seq) to define the heterogeneity of human T cells isolated from lungs, lymph nodes, bone marrow and blood, and their functional responses following stimulation. Through analysis of >50,000 resting and activated T cells, they reveal tissue T cell signatures in mucosal and lymphoid sites, and lineage-specific activation states across all sites including distinct effector states for CD8+ T cells and an interferon-response state for CD4+ T cells. Comparing scRNA-seq profiles of tumor-associated T cells to their dataset revealed predominant activated CD8+compared to CD4+ T cell states within multiple tumor types. Their results therefore establish a high dimensional reference map of human T cell activation in health for analyzing T cells in disease. For the entire paper, click here.