The article presents the literature review devoted to NOD2/CARD15 gene. Genetic variability affects the susceptibility and development of certain human diseases such as autoimmune diseases and infections, affecting numerous cellular processes, and thus modulating the response to environmental and internal factors. The NOD2/CARD15 gene plays a major role in the development and course of various diseases such as Grohn's disease, Blau syndrome, as well as the risk of developing severe complications of the graft versus host reaction after allogeneic stem cell transplantation. NOD (Nucleotide Oligomerization Domain) is the domain of nucleotide oligomerization. NOD-like receptors play an important regulatory role in the response on infectious agents and at activation of the adaptive immune response. It is known that the mechanism of action of NOD-like receptors is based on the response to the pathogen of associated molecular patterns mainly of bacterial origin, which leads to the formation and activation of inflammasome. Recently, another NOD-like receptor activation mechanism has been revealed that provides innate virus recognition. The review presents Toll-like receptors, which are part of the innate immune system. Innate immunity is an inherited system of protection of the body against pathogenic and non-pathogenic microorganisms. The mechanisms of innate immunity develop very quickly. In newborns, the immune system is mainly dependent on components of the innate or antigen-independent immune system including phagocytes, natural killer cells, antigen-presenting cells, humoral inflammatory mediators and complement system.

The article presents the review of the domestic and international researches devoted to one of the most «problem» aspects of pediatrics – to patients with recurrent infections (frequently ill children) and to their immune status (an immune imbalance). Children with recurrent infections (frequently ill children) are characterized by higher, than their peers, incidence of acute respiratory infection (ARI). ARI frequency up to 8 times a year can be a normal variant at favorable course, at the same time an immune imbalance is compensated by immune system.