Increased IL-4 receptor expression in COPD small airway remodelling

<bold>Introduction:</bold> IL-4 and IL-13 signal through the IL-4 receptor (IL-4R) which is expressed on immune cells and stromal cells. Small airway (SA) IL-4R expression in COPD is unclear. <bold>Methods:</bold> We compared the number of IL-4R positive cells in SA epithelium, lamina propria and smooth muscle between COPD patients (n=34) vs smoking controls (n=23) by immunohistochemistry. IL-4R expression in areas of epithelial remodelling (determined by increased epithelial thickening and presence of basal cell or goblet cell hyperplasia) was compared to areas of normal epithelium. Results were expressed per mm reticular basement membrane (epithelial counts) or per mm2 of tissue (lamina propria and smooth muscle). <bold>Results:</bold> IL-4R was expressed by basal and non-basal epithelial cells (including ciliated, goblet cell and intermediate cells). The number of IL-4R positive cells was significantly increased in areas of epithelial remodelling compared to normal epithelium in COPD patients and controls (approximately two-fold increase p<0.0001). No differences were observed between patient groups for the number of IL-4R positive cells in different airway compartments. <bold>Conclusion:</bold> IL-4R expression in COPD SA is increased in areas of remodelling. The regulation of IL-4R expression appears to be related to epithelial injury, repair and remodelling processes.