Results Table 1: Patient characteristics Patient characteristics: 17 patients with CF (7 boys; 8 girls, all dF508/dF50

1. EFFECT OF AN ACUTE BOUT OF EXERCISE ON INFLAMMATION IN CHILDREN WITH CYSTIC FIBROSIS • Van de Weert – van Leeuwen P.B.1, Beekman J.M.2, Van der Ent C.K.1, Hulzebos H.J.1, Arets H.G.M.1 • Cystic Fibrosis Centre, University Medical Center Utrecht, The Netherlands. • Molecular Immunology Lab, University Medical Center Utrecht, The Netherlands. Introduction Patients with cystic fibrosis (CF) suffer from pulmonary infections predominantly caused by Pseudomonas aeruginosa, leading to tissue damage, a decline in lung function and exercise capacity. Since exercise capacity has been identified as an independent predictor of morbidity and mortality in patients with CF, cardiopulmonary exercise testing (CPET) has been emphasized as important in evaluating and assessing prognosis and disease management. In healthy people exercise induces immunological responses that mimic those induced by other physical stressors. It induces transient increases in leukocytes and cytokines. It has been postulated that exercise induces immune tolerance with a reduced capacity of phagocytes to engulf bacteria, whereas others suggest the opposite. Aim: to investigate whether exercise in patients with CF has an effect on [1] inflammatory markers, [2] serum dependent binding and/ or phagocytosis of P. aeruginosa by neutrophils. Table 2: Differences in Leukocyte, leukocyte subsets, CRP and IgG levels induced by exercise Phagocytosis assay: Percentage of neutrophils that became FITC positive was not statistically significant different pre- and post-exercise (Figure 2). Figure 2: Top, left – Neutrophils with an increased FITC fluorescence were gated and counted by FACS analysis. Top, right – Serum dependent increase in FITC fluorescent neutrophils (n = 4) Bottom – Percentage of neutrophils of which FITC fluorescence increased. Methods Blood withdrawal: withdrawal before and after CPET. Inflammatory markers: Total leukocyte and subset counts, CRP, BSE and IgG levels. Differences were calculated with the Wilcoxon Signed Rank Test. Phagocytosis assay: capacity of neutrophils to phagocytose EGFP labelled P.aeruginosa (PAO1) was determined after 30 min opsonisation and an additional 30 min of phagocytosis. Leukocytes were derived from whole blood from healthy controls, serum from patients with CF. Proportion leukocytes:bacteria was 1:10. 2% serum was added in 2 conditions: with and without heat-inactivation (complement inactivated). The percentage of neutrophils with increased FITC fluorescence was counted by flow cytometry analysis, what indicates binding/ phagocytosis to EGFP labelled P. aeruginosa. ResultsTable 1: Patient characteristics Patient characteristics: 17 patients with CF (7 boys; 8 girls, all dF508/dF508). Inflammatory markers: Exercise induced significant increases in all leukocyte subsets, of which NK cells increased most (Figure 1, Table 2). Significant increases were also seen for IgG, IgG1, IgG2 and IgG3 levels, but not for CRP and IgG4 levels (Table 2). Figure 1: Percent increase in leukocyte en leukocyte subsets (median, IR) Conclusion In patients with CF exercise leads to a leukocytosis dominated by NK cells, which is comparable to that seen in healthy controls. Although binding/ phagocytosis of P. aeruginosa by neutrophils is dependent of IgG, the exercise induced significant increases in IgG and IgG subtype levels did not change the capacity of neutrophils to bind and/ or engulf P. aeruginosa. Correspondence p.b.vanleeuwen-3@umcutrecht.nl Cystic Fibrosis Centre, University Medical Centre Utrecht, Room KH.01.419.0, P.O.box 85090 3508 AB Utrecht