Role of Innate Lymphocytes in Infection and Inflammation

Abstract

Cooperation between the innate and adaptive immune responses is critical for enabling protective immunity against various invading microbes. Distinct types of effector T cells have different functions in adaptive immune responses. Th1 cells play important roles in the control of intracellular bacteria by producing IFN-γ to activate macrophages and in anti-viral immunity by producing IFN-γ and activating cytotoxic T lymphocytes. Th2 cell-derived cytokines are important in activating mast cells, eosinophils, and goblet cells in anti-helminth immunity. Th17 cells are pivotal for the inflammatory response mediated by neutrophils, which resists extracellular bacterial infection. In all cases, it is critical that the innate immune responses limit the growth and expansion of invading microbes until antigen-specific adaptive immune responses are established. Recent studies have identified multiple subsets in innate lymphocytes corresponding to previously defined Th subsets. Classical natural killer cells, RORγ+ lymphoid tissue inducer-related cells, and Th2-type innate lymphocytes play distinct roles in innate immune responses by producing Th1, Th17, and Th2 cytokines, respectively. Cooperation between innate lymphocytes and antigen-specific T and B cells are likely important in protective immunity against distinct types of microbes. The most recently identified subset is the RORγ-independent Lin−Thy-1+IL-7R+GATA3+ innate lymphocyte subset such as natural helper (NH) cell, which is Id2- and IL-7-dependent. This population produces Th2 cytokines, most notably IL-5 and IL-13, and plays a major role in innate immune responses during anti-helminth immunity. In addition, these cells are likely involved in the pathophysiology of some types of allergic diseases. We summarize here current knowledge regarding various innate lymphocyte subsets. In particular, we focus on the Th2-type innate lymphocyte subset.

Development, Differentiation, and Diversity of Innate Lymphoid Cells

“…IL-25, IL-33 and thymic stromal lymphopoietin (TSLP), all of which are epithelial cell-derived cytokines, regulate type 2 innate immune responses against helminths and pathophysiology of airway allergens (Koyasu and Moro, 2012). The existence of lineage-negative innate immune cells producing type 2 cytokines was first reported by Fort et al .…”

Increased percentage of IFN-γ producing CD56+CD3+ cells in active tuberculosis patients upon CFP-10 stimulation of peripheral mononuclear cells

“…NKT cells act as a bridge between the innate and adaptive immune response due to their ability to activate several cells of the innate response, as well as cells of the adaptive response through cytokines production [36]. Furthermore, NKT cells restricted to CD1d are divided in two major groups.…”

Characteristics of innate lymphoid cells (ILCs) and their role in immunological disorders (an update)

“…Nowadays, based on their common characteristics, these type 2 cytokine producing cells entitled ILC2 [2,11]. These cells also called natural helper cells (NHCs), nuocyte and innate helper 2 (IH2) cells that are found in the mesenteric fat-associated lymphoid cluster, liver, spleen, Peyer ' s patches and airway mesenteric lymph nodes [2,25]. For the first time, ILC2s were discovered in the fetal gut tissue in human.…”