TNF and cystic fibrosis: Indeed, it has been reported that TNFα sustains the recruitment and activation of both neutrophils and macrophages, contributing to establishment and exacerbation of the chronic inflammatory state in different organs [27,40]; in contrast, a decrease in the levels of this cytokine (which we observed in CF patients regularly undertaking PA) may substantially contribute to reduction of the recruitment of immune cells and thus the inflammatory process [27,40].