Innate and adaptive immune responses in asthma

The recognition that asthma is primarily an inflammatory disorder of the airways associated with T helper type 2 (T(H)2) cell-dependent promotion of IgE production and recruitment of mast cells and eosinophils has provided the rationale for disease control using inhaled corticosteroids and other anti-inflammatory drugs. As more has been discovered about the cytokine, chemokine and inflammatory pathways that are associated with T(H)2-driven adaptive immunity, attempts have been made to selectively inhibit these in the hope of discovering new therapeutics as predicted from animal models of allergic inflammation. The limited success of this approach, together with the recognition that asthma is more than allergic inflammation, has drawn attention to the innate immune response in this disease. Recent advances in our understanding of the sentinel role played by innate immunity provides new targets for disease prevention and treatment. These include pathways of innate stimulation by environmental or endogenous pathogen-associated molecular patterns (PAMPs) and danger-associated molecular patterns (DAMPs) to influence the activation and trafficking of DCs, innate sources of cytokines, and the identification of new T cell subsets and lymphoid cells.