Chi3l1: New kid on the T cell blockade

T cell-excluded tumors are less responsive to immunotherapies. In this issue of Immunity, Taifour et al. show that secretion of the cytokine Chi3l1 by tumor cells induces T cell exclusion via neutrophil extracellular trap (NET) formation. Chi3l1 depletion stimulates T cell infiltration and synergizes with PD-1 blockade.