Circulating cytokine levels in systemic sclerosis related interstitial lung disease and idiopathic pulmonary fibrosis

Exploration of cytokine levels in systemic sclerosis-associated interstitial lung disease (SSc-ILD) and idiopathic pulmonary fibrosis (IPF) is needed to find common and diverse biomolecular pathways. Circulating levels of 87 cytokines were compared amongst 19 healthy controls and consecutive patients with SSc-ILD (n = 39), SSc without ILD (n = 29), and IPF (n = 17) recruited from a Canadian centre using a log-linear model adjusted for age, sex, baseline forced vital capacity (FVC), and immunosuppressive or anti-fibrotic treatment at time of sampling. Also examined was annualized change in FVC. Four cytokines had Holm's corrected p-values less than 0.05. Eotaxin-1 levels were increased approximately two-fold in all patient categories compared to healthy controls. Interleukin-6 levels were eight-fold higher in all ILD categories compared to healthy controls. MIG/CXCL9 levels increased two-fold more in all but one patient category compared to healthy controls. Levels of a disintegrin and metalloproteinase with thrombospondin type 1 motif, member 13, (ADAMTS13) were lower for all categories of patients compared to controls. No substantial association was found for any of the cytokines with FVC change. Observed cytokine differences suggest both common and diverse pathways leading to pulmonary fibrosis. Further studies evaluating longitudinal change of these molecules would be informative.