Person:

Karwacz, Katarzyna

T cell receptor (TCR) down-modulation after antigen presentation is a fundamental process that regulates TCR signal transduction. Current understanding of this process is that intrinsic TCR/CD28 signal transduction leads to TCR down-modulation. Here, we show that the interaction between programmed cell death 1 ligand 1 (PD-L1) on dendritic cells (DCs) and programmed death 1 (PD-1) on CD8 T cells contributes to ligand-induced TCR down-modulation. We provide evidence that this occurs via Casitas B-lymphoma (Cbl)-b E3 ubiquitin ligase up-regulation in CD8 T cells. Interference with PD-L1/PD-1 signalling markedly inhibits TCR down-modulation leading to hyper-activated, proliferative CD8 T cells as assessed in vitro and in vivo in an arthritis model. PD-L1 silencing accelerates anti-tumour immune responses and strongly potentiates DC anti-tumour capacities, when combined with mitogen-activated kinase (MAPK) modulators that promote DC activation.

Despite their importance, the molecular circuits that control the differentiation of naïve T cells remain largely unknown. Recent studies that reconstructed regulatory networks in mammalian cells have focused on short-term responses and relied on perturbation-based approaches that cannot be readily applied to primary T cells. Here, we combine transcriptional profiling at high temporal resolution, novel computational algorithms, and innovative nanowire-based tools for performing perturbations in primary T cells to systematically derive and experimentally validate a model of the dynamic regulatory network that controls Th17 differentiation. The network consists of two self-reinforcing, but mutually antagonistic, modules, with 12 novel regulators, whose coupled action may be essential for maintaining the balance between Th17 and other CD4+ T cell subsets. Overall, our study identifies and validates 39 regulatory factors, embeds them within a comprehensive temporal network and reveals its organizational principles, and highlights novel drug targets for controlling Th17 differentiation.