IL13 and idiopathic pulmonary fibrosis: Alarmins (IL-25, TSLP) are the earliest cytokines secreted following tissue damage and they contribute to fibrosis indirectly with actions from type 2 cytokine-secreting immune cells, such as NKT2, ILC2, CD4+Th2 cells, etc. Thus IL-25 and IL-13 secreting ILC2 are also found in IPF patients (104).