TGFB2 and COVID-19: Expression of ST2 can likewise be favoured by TGFβ2, which is also increased in the bronchoalveolar lavage fluid of patients with COVID-19, and might further enhance ST2 expression in innate lymphoid cells: IL-33 is the key cytokine that drives these cells to differentiate into type 2 innate lymphoid cells (ILC2s) [74,75].