The expression of IL17RA (the common subunit of IL-17A and IL-25 receptor) on sputum macrophages in asthma patients

<b>Background:</b> IL-17A and IL-25 (IL-17 cytokines family) play an important role in the development of asthma, and allergy. Both cytokines act by binding to heterodimeric receptors, whose common subunit is IL17RA. This receptor is found on macrophages and some other cell types. The aim of the study was to determine the expression of IL17RA on induced sputum (IS) CD206+ macrophages (M2 type) from asthmatics and controls with regard to IL-17/IL-25 background and relation to clinical features of the disease. <b>Methods:</b> The study enrolled 34 asthma patients and 34 controls. The expression of CD206 and IL17RA on IS macrophages was assessed by the immunofluorescence method. In the IS supernatant, IL-17A and IL-25 levels were evaluated (ELISA method). <b>Results:</b> An elevated expression of IL17RA on IS macrophages in asthmatics vs controls was found. In asthmatics, CD206+IL17RA+ macrophage percentage was significantly higher than in healthy subjects and correlated positively with total IgE level. A characteristic sputum profile of atopic asthmatic was as follows: high CD260+IL17RA+ macrophage percentage, elevated IL-25 level and low CD206+IL17RA- macrophage percentage. <b>Conclusion:</b> It seems that M2 rather than M1 type macrophages are the effector cells expressed common subunit of the receptor for IL-17A and IL-25 in asthma. This may be related to the Th2-environment in asthma and increased concentrations of IL-25 and IL-13 as well as eosinophils. To our knowledge, our study provides the first data on a possible link between immunological reaction orchestrating M2 macrophages and IL-25 via IL-17RA pathway in the asthmatic airways.