Zdorovʹe Rebenka (Oct 2020)
The importance of innate lymphoid cells in the development of meta-inflammation of adipose tissue in obesity
Abstract
The literature review presents modern ideas about the role of innate lymphoid cells in the development of meta-inflammation of adipose tissue in obesity, which has recently become epidemic, especially in the adolescent group. The article presents the data on the organization of the population of innate lymphoid cells (ILC), which, according to the spectrum of their subpopulations, represent, as it were, an innate cellular analogue of CD4+ T-lymphocytes cells but do not express antigen receptors and are not capable of clonal expansion. The main types of ILCs are presented, namely ILC1, which are analogous to Th1 cells, ILC2 — Th2 cells, and ILC3 — Th17 and Th22 cells, as well as their main functional properties and structural features. The development of obesity is accompanied by an increase in the representation of NK cells, ILC1, and a decrease in the amount of ILC2 in the epididymal adipose tissue. The presented data indicate that the main function of the ILC1 group is a high level of expression of IFN-γ and TNF-α, which has a defining role of protection against intracellular pathogens, and the use of specific markers CD49a, CD127 (IL-7Rα), and Eomes makes it possible to distinguish ILC1 from NK cells. At the same time, the relatively high content of ILC2 in physiological adipose tissue is a necessary cellular mechanism that maintains the anti-inflammatory state of adipose tissue as an organ with a high content of pro-inflammatory molecular triggers. An increase in the populations of NK cells and ILC1 promotes the accumulation and activation of both M1 Mϕ and Th1 cells. The decrease in the ILC2 level is accompanied by a decrease in the M2 Mϕ and eosinophil pools. GATA3 acts as a key transcription factor for the development and functioning of ILC2. The ILC3 population is represented by cells expressing the transcription factor RORγt and producing IL-22. The ILC3 population plays a dual role: due to the production of IL-22, it prevents the process of inflammation, and due to the production of IL-17, it promotes the development of meta-inflammation. Thus, it can be assumed that the population of innate lymphoid cells is involved in the fine regulation of the functioning of the effector cells of the immune system. In the physiological state of the population, the ILC maintains a “state of rest”, and in the development of obesity, the mechanisms of elimination of hypertrophied adipocytes.
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