Modulation of Type 2 Inflammation by Sensing Immunomodulatory RNA in House Dust Mite and Viruses

The incidence of allergic diseases has been increasing over the past few decades worldwide. Although allergic reactions are often characterized by an overzealous Th2 inflammatory response, the underlying mechanisms remain poorly defined. House dust mite (HDM) is one of the most common indoor allergens that cause allergic diseases such as asthma. Recent studies suggest that innate immunity activated by HDM allergens is critical for driving the development of a polarized type 2 response. HDM harbors not only allergic protein antigens, but also non-protein microbial products, e.g., LPS or dsRNA, which can trigger innate immune responses that either promote a type 2 inflammatory phenotype or suppress a severe type 2 immunopathologies in mice, respectively. In this review, we discuss how the innate sensing of immunomodulatory RNA in HDM allergens and viruses modulates type 2 inflammatory responses.