Lysosomal cationic proteins as the basis of cellular and humoral immunity of animals: the role of neutrophil extracellular traps (NETs) in immune homeostasis (review)

Relevance. Lysosomal cationic proteins (LCP) of granulocytic leukocytes: elastase, cathepsin G, proteinase-3, calgranulin, cathelicidins, defensins, lactoferrin, protegrins are active against viruses, bacteria, fungi, protozoa. The issues of physiological regulatory, immune and pathological effects of LCP and their derivatives – neutrophil (heterophil) extracellular traps (NETs) on pathogens, healthy cellular and tissue structures of the body are noted. Results. The increment of LCP granulocytes is realized by: 1. merocrine type — by degranulation; 2. exocytosis and false degranulation, that is, the process of decationization of lysosomes containing granules of cationic proteins with apocrine or holocrine type of secretion. Decationization implements exocytosis of LCP, extrusion of intact lysosomes from the cell with LCP, and diffusion of LCP through the lysosome membrane. Lysosome degranulation reactions with LCP form phagolysosomes and initiate phagocytosis, lysosome decationization reactions with LCP ensure the formation and functions of NETs. NETs is formed by non-lytic (non-lytic) and lytic (lyzed) pathways in septic and aseptic inflammation, with the ontogenetic development of immune links. NETs is stereotypically formed intravascular during aseptic inflammation, oxidative stress and in a physiological regime, when granulocytes are stimulated by products of oxidative metabolism. Using a cytochemical test with a highly sensitive acid-base bromophenol blue indicator, subcellular and cellular manifestations of the physiological age-related immune activity of cationic proteins accumulated in granulocyte lysosomes were studied on the avian model organism (Aves), and nonspecific adaptive reactions (NAR) of vertebrates in early postnatal ontogenesis were studied. The basis for the formation of NAR is the relationship of groups of leukocytes (lymphocytes, monocytes and granulocytes) with the dynamics of their lysosomal cationic proteins. The method for calculating the level of activity and potential capabilities of granulocytes in phagocytic reactions and in the formation of .NETs includes indices characterizing the directions and intensity of immune reactions of granulocytes, taking into account the processes: 1. degranulation of lysosomes with LCP — in the initiation of the cellular phagocytic link; 2. decationization of lysosomes with LCP — in the initiation of extracellular traps involved in the implementation of the humoral link of immunity.