Novel Concepts on Allergic Rhinitis: From Pathogenesis to Treatment

Atopic diseases like allergic rhinitis, atopic asthma, and atopic dermatitis are prevalent and on the rise. The need to understand the pathogenesis better is central to the development of newer therapeutic strategies. Conventional knowledge tells us that mast cells are only important in the immediate phase allergic reaction and that T cells orchestrate the late phase allergic reaction. Yet, in recent years, much evidence has accumulated on the versatile role of mast cells in allergic inflammation. Here, we describe the novel roles of mast cells and T cells in allergic inflammation; Like T cells, mast cells in the allergic nasal mucosa are a profound source of Th2 type cytokines and can induce IgE synthesis. Mast cells can also enhance self activation in an autocrine manner via the IL-4 and IgE-induced upregulation of the high affinity IgE receptor (FcepsilonRI) and interaction with the extracellular matrix proteins. Mast cells are also capable of modulating the function of other cells, like epithelial cells. Hence, it is increasingly evident that mast cells contribute to various arms of allergic inflammation. Of the T cells, those of the gammadelta phenotype are increased at sites of allergic inflammation, and potentially play a role at various steps of the allergic inflammation. Thus mast cells and gammadelta T cells may play crucial roles as both effector and immunoregulatory cells in perpetuating allergic inflammation. The strategy of management of allergic rhinitis includes optimal allergen avoidance followed by pharmacotherapy or immunotherapy. This is complemented with patient education, and surgery in selected cases. However, a significant proportion of patients with rhinitis also have associated asthma or minimal persistent inflammation in the lower airways. Since the IgE-IgE receptor network, a central component of the allergic inflammation, novel therapies like the humanized Anti-IgE monoclonal antibodies which target this component of the allergic inflammation may play an important role in the treatment of allergic diseases.