Finally, GM-CSF being the eosinophil survivalpromoting cytokine together with IL-5 can up-regulate allergic eosinophil-mediated inflammation in the middle ear (Fig. 6) . However, in the past year of investigations GM-CSF has been shown as a potential down-regulator of allergic inflammation, because GM-CSF induced apoptosis of human eosinophils through the eosinophil receptor Siglec-8 (sialic acid binding immunoglobulin-like lectin). 119 Thus, GM-CSF can be a very important regulator of the middle ear inflammation and additional experimental work needs to be done to clarify the exact role of this cytokine in the pathogenesis of chronic OME.