Increased response of blood eosinophils to various chemotactic agents in quiescent Crohn disease

Background: The number of eosinophils is increased in the mucosae of the di gestive and the respiratory tracts in Crohn disease, even clinically quiesc ent. The mechanisms underlying this panmucosal eosinophilia are unknown. Me thods: The response of blood eosinophils to various chemotactic agents was assessed in 15 patients with clinically quiescent Crohn disease. The result s were compared with 15 healthy controls. After purification, eosinophils w ere placed in Boyden microchambers and the chemotactic effect of PAF (10(-7 ) hi), RANTES (50 ng/ml), IL-5 (0-20 ng/ml), IL-8 (0-50 ng/ml), Eotaxin (0- 50 ng/ml) was evaluated. The number of eosinophils in induced sputum of the se Crohn disease patients and controls was also assessed and the correlatio n between chemotaxis and eosinophil count in induced sputum was studied. Re sults: PAF and RANTES induced a chemotactic effect both in Crohn disease pa tients and controls. The chemotactic index was significantly higher in Croh n than controls for PAF (2.09 +/- 0.24 versus 1.37 +/- 0.14: P < 0.05) but not RANTES. With IL-5, IL-8 and Eotaxin, there was no detectable chemotacti c effect in controls while in Crohn, we observed a significant dose-depende nt chemotactic effect. Furthermore, with Eotaxin 50 ng/ml, the chemotactic index was significantly higher in Crohn disease patients than controls (2.4 2 +/- 0.18 versus 1.56 +/- 0.28; P < 0.05). A significant increase in sputu m eosinophil count and a significant decrease in sputum macrophage count in Crohn disease were observed. However, there was no correlation between eos inophil chemotaxis and sputum eosinophil count in individual patients. Conc lusion: There is an increased response of blood eosinophils to various chem otactic agents, mainly PAF and Eotaxin, in clinically quiescent Crohn disea se. This may participate in the mucosal infiltration by eosinophils in this disease.