Type 2 innate lymphoid cells (ILC2s) are known to help initiate and coordinate allergic and anthelmintic immunity. Recent studies have also pointed to the role that ILC2s play in the promotion and inhibition of various cancers. Jacquelot et al. show that in melanoma, ILC2s infiltrate tumors and control antitumor immunity. Tumor-infiltrating ILC2s produce the proinflammatory cytokine GM-CSF, which in turn enhances the recruitment, activation, and survival of anti-melanoma eosinophils. Notably, these ILC2s also express programmed cell death protein-1 (PD-1), which dampens their antitumor activity. When the authors combined anti–PD-1 immunotherapy with administration of the ILC2-activating cytokine interleukin-33 in a mouse model of melanoma, they saw better antitumor responses. ILC2 and eosinophil accumulation in tumors correlated with improved melanoma patient survival, suggesting that these cell populations have potential as cancer immunotherapy targets.
Nat. Immunol. 22, 851 (2021).