IL13 and idiopathic pulmonary fibrosis: In bronchoalveolar lavage fluid from patients with IPF, IL-13 levels were elevated compared with normal controls, and IL-13 levels were negatively correlated with key measures of lung function, such as % predicted FVC and % predicted diffusing capacity for carbon monoxide (DLCO), suggesting pathogenic functions of IL-13 in patients with IPF [18].