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.

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. Here, we demonstrate 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. We believe our work provides insights into the initiation of T cell responses in the spleen and their consequences for T cell differentiation.

Alternative splicing modulates autoinhibition and SH3 accessibility in the Src kinase Fyn.

Src family kinases are central regulators of a large number of signaling pathways. To adapt to the idiosyncrasies of different cell types, these kinases may need a fine-tuning of their intrinsic molecular control mechanisms. Here, we describe on a molecular level how the Fyn kinase uses alternative splicing to adapt to different cellular environments. Using structural analysis, site-directed mutagenesis, and functional analysis, we show how the inclusion of either exon 7A or 7B affects the autoinhibition of Fyn and how this changes the SH3-dependent interaction and tyrosine phosphorylation of Sam68, with functional consequences for the Sam68-regulated survival of epithelial cells. Our results illustrate a novel mechanism of evolution that may contribute to the complexity of Src kinase regulation.