Matrix reboot: IL-17 signals CAFs to create a second tumor T cell checkpoint.

Excessive collagen deposition by fibroblasts surrounding some tumors has seriously limited the efficacy of checkpoint inhibitor therapies. Chen et al. (2022. J. Exp. Med.https://doi.org/10.1084/jem.20210693) show that IL-17 promotes collagen deposition by cancer-associated fibroblasts, enhancing immune exclusion of tumors, and that targeting IL-17-triggered HIF1α expression can reverse matrix mediated immune exclusion.