Role of the immune cells, mediators and cytokines in pathogenesis of asthma: a review article

Asthma is a chronic inflammatory disorder of the airways, associated with airway re-modeling and hyperresponsiveness. It is expressed that asthma influences about 300 million people around the world, which is estimated to increase to about 400 million by 2025. The prevalence rate is 15 to 20 percent in children and 5 to 10 percent in adults, while its trend is still increasing. Inflammation plays an important role in the patho-physiology of asthma, which involves an interaction of different types of the immune cells and mediators. It leads to a number of pathophysiology changes, including bron-chial inflammation, airway obstruction, and clinical episodes such as cough, wheeze and shortness of breath. Asthma is now greatly being introduced as a heterogeneous disorder and it is pointed out to the role of T cells, including Th1, Th2, Th17, and regu-latory T cells. Other immune cells, especially neutrophils, macrophages and dendritic cells, as well structural cells such as epithelial and airway smooth muscle cells also pro-duce disease-associated cytokines in asthma. Increased levels of these immune cells and cytokines have been recognized in clinical samples and mouse models of asthma. Different cytokines, including pro-inflammatory cytokines (such as TNFα, IL-1, and IL-6), T helper 2 cytokines (such as IL-4, IL-5, IL-9, IL-13), and growth factors (such as GM-CSF, PDGF) play a role in the pathogenesis of asthma. Indeed chemokines (such as MPC-1, RANTES , MIP-1) and the chemokine receptors (such as CCR3, CCR4, CCL11, CCL24, and CCL26) play an important role in the recruitment of circu-lating inflammatory cells into the airways in asthmatic patients and also is related with increased T helper 2 cytokines after inhaled allergens. Among new approaches, treat-ment of asthma with anti-cytokine drugs such as antibodies blocking IL-4, IL-5, IL-9 could reduce recruitment inflammatory cells into the airways and remodeling. The final perspective of asthma treatments would be to alter from the symptomatic treatments to disease modifying