Abstract

T helper type 2 (TH2) cells were previously thought to be the main initiating effector cell type in asthma; however, exaggerated TH2 cell activities alone were insufficient to explain all aspects of asthma. Asthma is a heterogeneous syndrome comprising different phenotypes that are characterized by their different clinical features, treatment responses, and inflammation patterns. The most-studied subgroups of asthma include TH2-associated early-onset allergic asthma, late-onset persistent eosinophilic asthma, virus-induced asthma, obesity-related asthma, and neutrophilic asthma. The recent discovery of human innate lymphoid cells capable of rapidly producing large amounts of cytokines upon activation and the mouse data pointing to an essential role for these cells in asthma models have emphasized the important role of the innate immune system in asthma and have provided a new means of better understanding asthma mechanisms and differentiating its phenotypes.

Highlights

  • The immune system is classically divided into two categories, innate and adaptive immunity, according to the speed and the duration of the response, and they collaborate with each other to target different agents and perform effector functions

  • Through recent advances in understanding the different subsets of immune system effector cells, Annunziato et al have recently suggested a new classification [1]. They proposed that the innate and adaptive immune systems could be generally classified into three major kinds of cell-mediated effector immunity: categorized as type 1, comprising T-bet+ IFN-γ–producing helper cells, type 2, composed of GATA-3+ lymphocytes producing interleukin-4 (IL-4), IL-5, and IL-13, and type 3, characterized by RORγt+ lymphocytes that produce IL-17 alone or in combination with IL-22 as signature cytokines [1]

  • We provide an updated view on the emerging roles of non-cytotoxic Innate lymphoid cells (ILCs) in different asthma phenotypes

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Summary

Introduction

The immune system is classically divided into two categories, innate and adaptive immunity, according to the speed and the duration of the response, and they collaborate with each other to target different agents and perform effector functions. Asthma includes complex innate and adaptive immune responses to environmental factors. ILC1s and its possible role in asthma phenotypes ILC1s, formerly known as conventional NK cells, are present in mucosal tissues, express the IL-7 receptor, and rapidly secrete IFN-γ upon stimulation with IL-12 and IL-18, which are produced by macrophages and other cells.

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