[The role of HLA genes: from autoimmune diseases to COVID-19]

Genes of HLA system (Human Leukocyte Antigen) play an essential role in the normal functioning of the immune system. There are three classes of genes: I, II, and III. The function of HLA molecules class I is to present antigens of peptides from the cytoplasm to T-lymphocytes on the cell surface, and class II - to present antigens of peptides from the extracellular space. In the classical view, the pathological activation of the immune system in patients with a genetic predisposition can result in the development of autoimmune diseases. However, the influence of this system on the development of non-autoimmune diseases, their severity and prognosis, has been recently considered. Besides, HLA molecules provide a presentation of various infectious agents. In this connection, the loci of the main histocompatibility complex can be considered candidates for determining the genetic predisposition to infectious diseases themselves and their course. This review hypothesizes that specific variants of HLA genes may cause the formation of a «cytokine storm» in patients with COVID-19. Identification of a group of patients with particular genetic variations that cause violation of immune tolerance and hyperresponse in the setting of viral infection will help to optimize the algorithm for disease prevention and treatment of such patients and, as a result, to reduce the severity of the epidemiological situation.