Tumor-infiltrated NK cells operate under hypoxia and rely on HIF-1 to cytokine production and tumor cell death induction.31 HIF-1 activation also directly affects late ILC2 maturation through the IL33-ST2 signaling pathway.32 Together, our results and published reports highlight the relevance of the HIF-1 pathway for steady state immune system functions in intestinal mucosa and lymphoid tissue, and in tumoral, ischemic and inflamed environments. The gene discussed is IL33; the disease is neoplasm.