ptomic analyses of bronchoalveolar lavage fluid from patients with COVID-19 have revealed a strong upregulation of IL-33.11 IL-33 is a cytokine of the IL-1 family that is expressed in barrier tissues and exerts pleiotropic functions. In the lungs, IL-33 is promptly released, mainly by injured epithelial alveolar cells, following infection and cellular damage.12 Among its functions, IL-33 enhances TGFβ-mediated differentiation of Foxp3+ regulatory T (Treg) cells13 and stimulates CD11c+ myeloid dendritic cells to secrete IL-2, which drives Treg cell expansion, thus ultimately promoting reso