Carl Figdor and colleagues, theme Cancer development and immune defense, provide insights into the initiation of T cell responses in the spleen and their consequences for T cell differentiation. They have published their results inProceedings of the National Academy of Sciences USA. Mounting an effective immune response relies critically on the coordinated interactions between adaptive and innate compartments. How and where immune cells from these different compartments interact is still poorly understood. They demonstrated that the cross-talk between invariant natural killer T cells (iNKT) and CD8+ T cells in the spleen, essential for initiating productive immune responses, is biphasic and occurs at 2 distinct sites. Codelivery of antigen and adjuvant to antigen-presenting cells results in: 1) initial short-lived interactions (0 to 6 h), between CD8+ T cells, dendritic cells (DCs), and iNKT cells recruited outside the white pulp; 2) followed by long-lasting contacts (12 to 24 h) between iNKT cells, DCs, and CD8+ T cells occurring in a 3-way interaction profile within the white pulp. Both CXCR3 and CCR4 are essential to orchestrate this highly dynamic process and play nonredundant in T cell memory generation. While CXCR3 promotes memory T cells, CCR4 supports short-lived effector cell generation.
Cross-talk between iNKT cells and CD8 T cells in the spleen requires the IL-4/CCL17 axis for the generation of short-lived effector cells