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Background: Many patients with cystic fibrosis (CF) suffer from allergic disease, which can complicate treatment of CF lung disease. Interleukin (IL)-4 and IL-13 have been shown to be important mediators in allergic disease., Objective: To investigate the role of IL-4 and IL-13 in allergic and non-allergic CF patients., Methods: Expression of IL-4 and IL-13 mRNA was investigated in peripheral blood mononuclear cells (PBM) of seven CF patients with allergy, of six patients without allergy and of nine healthy subjects as well as in BAL cells of four patients and of all controls. PBM from six patients were incubated with recombinant human IL-13 or human antiIL-13 antibody without and with LPS stimulation and TNFalpha levels were measured by ELISA., Results: IL-13 mRNA expression was increased in allergic and non-allergic patients compared to controls. No significant difference in IL-4 expression could be found between patients and controls. Addition of IL-13 decreased TNFalpha in PBM culture supernatants., Conclusion: Our data suggest that IL-13 rather than IL-4 might play an important role in both allergic and non-allergic CF patients. IL-13 might also compromise host defence by decreasing TNFalpha production., (Copyright 2003 European Cystic Fibrosis Society)

Background: Sarcoidosis is a systemic granulomatous disorder of unknown origin. Lymphocytic inflammation is dominated by expression of Th1 type cytokines such as tumour necrosis factor alpha (TNFalpha). Interleukin 13 (IL-13) is a Th2 cytokine which is expressed by CD4+ T cells and has been shown to suppress TNFalpha in human blood monocytes. The role of IL-13 as a possible anti-inflammatory cytokine in sarcoidosis was investigated., Methods: mRNA expression of IL-13, IL-4, IL-10, and TNFalpha in bronchoalveolar lavage (BAL) fluid cells and peripheral mononuclear blood cells (PBM) of 18 patients with sarcoidosis and nine healthy controls was assessed using RT-PCR. In addition, IL-13 protein levels in BAL cell culture supernatants from 12 patients and all controls were measured and immunocytochemistry of IL-13 protein was performed in BAL fluid cells of eight patients. TNFalpha concentrations were measured with and without stimulation with recombinant human (rh) IL-13, rhIL-10, and lipopolysaccharide (LPS)., Results: IL-13 mRNA expression was significantly increased in BAL cells and PBM of patients compared with controls (p<0.05). No significant difference was found in IL-4 mRNA or IL-10 mRNA expression in BAL fluid cells or PBM between the two groups. TNFalpha mRNA expression was significantly higher in BAL fluid cells of patients than controls (p<0.05). IL-13 protein levels in BAL cell culture supernatants were slightly raised in half the patients investigated but in only two controls. Immunocytochemistry detected IL-13 protein in alveolar macrophages of patients. IL-13 led to decreased TNFalpha concentrations (p<0.05)., Conclusions: IL-13 expression is increased in BAL cells and PBM in sarcoidosis and IL-13 is secreted from BAL cells. Alveolar macrophages may be the cellular source. These data suggest that IL-13 might have an anti-inflammatory effect by acting on TNFalpha.