Background: Inflammatory response in pulmonary fibrosis closely resembles a T-helper (Th) 2 immune response. For recruitment to an inflammatory lesion, the majority of Th1 cells express CXC chemokine receptor 3, recognizing monokine induced by interferon-gamma (Mig), interferon gamma-inducible protein of 10 kD (IP-10), and interferon-inducible T-cell alpha chemoattractant (I-TAC). Th2 cells express CC chemokine receptor 4, recognizing thymus- and activation-regulated chemokine (TARC) and macrophage-derived chemokine (MDC). We investigated the Th1/Th2 chemokine production patterns by lung fibroblasts and their evaluation in bronchoalveolar lavage (BAL) fluid of interstitial lung disease.
Methods: The production pattern of Th1/Th2 chemokines by lung fibroblasts was examined in ELISA and quantitative reverse transcriptase polymerase chain reactions. Th1/Th2 chemokine levels in BAL fluid of idiopathic pulmonary fibrosis (IPF) and nonspecific interstitial pneumonia (NSIP) were examined to evaluate the clinical relevance of Th1/Th2 chemokines.
Results: The lung fibroblasts were polarized to produce Th1-type chemokines by the pro-inflammatory cytokine, tumor necrosis factor (TNF)-alpha and the anti-fibrotic cytokine, interferon (IFN)-gamma. However, the induction patterns of chemokines by these two cytokines were different, i.e., involving predominant induction of IP-10 and I-TAC by TNF-alpha and induction of Mig by IFN-gamma. Although Mig, IP-10, and I-TAC were produced within the BAL fluid of patients, TARC and MDC were at significantly low levels.
Conclusions: Our results suggest that lung fibroblasts tend to induce a Th1-type immune response under normal conditions, and that a Th2-type immune response does not play a significant role in smoldering inflammation around the established lesions in IPF and NSIP.