BackgroundTransforming growth factor beta 1 (TGF&bgr;1) is a major fibrogenic cytokine, the expression of which is increased in the livers of children with cystic fibrosis liver disease (CFLD) and in the bronchoalveolar lavage fluid of patients with cystic fibrosis pulmonary disease (CFPD). The purpose of our study was to investigate the usefulness of plasma TGF&bgr;1 as a noninvasive marker of CFLD and CFPD, or both and to investigate the contribution of platelet-derived TGF&bgr;1 to plasma TGF&bgr;1 by correlating the latter with platelet factor 4 (PF4).MethodsThree groups of patients with cystic fibrosis were studied: 1) those with CFLD, 2) those with CF and no liver disease (CFNLD), and 3) those with CFPD. Controls were healthy adolescents and adults. Plasma TGF&bgr;1 was assayed using the R and D Quantikine quantitative sandwich enzyme immunoassay technique and PF4 (American Bioproducts ELISA kit).ResultsPlasma TGF&bgr;1 was markedly increased in CFPD (15 ± 3 ng/mL) versus healthy adults (1 ± 0 ng/mL;P< 0.004. The PF4 values followed a similar pattern: 105 ± 8 ng/mL in CFPD versus 12 ± 4 ng/mL (P< 0.0001). Plasma TGF&bgr;1 values in CFLD did not differ from CFNLD patients of comparable age nor from values for healthy adolescents. Plasma TGF&bgr;1 values were strongly correlated with values for PF4:r= 0.543,P< 0.0001.ConclusionsPlasma TGF&bgr;1 is not a useful marker of CFLD. The increased plasma TGF&bgr;1 and PF4 in CFPD patients are of interest both as possible noninvasive markers of pulmonary fibrosis and because the increased values suggest that platelet activation may play a pathogenetic role in CFPD.