Natural killer (NK) cells are cytotoxic lymphocytes which constitute a significant element of innate immune responses against tumours and cells infected with viruses or parasites. The function of NK cells is tightly regulated and depends on the balance between activating and inhibitory signals. This review focuses on the latest research showing a high redundancy of mechanisms regulating the activity of NK cells during viral infections and indicating their involvement in the adaptive immune response.
This paper illustrates elements of innate immunity, such as recently described natural T 2 cells (nT 2 or NHC), nuocytes, innate type 2 helper cells (Ih2), multi-potent progenitor type 2 cells (MMPtype2 cells), and IL-36 that is very similar to IL-36. Populations of these cells are involved in the development of Th2 cytokine responses and participate in course of allergic processes and in host defense against microorganisms and parasites. All four populations lack expression of surface markers characteristic for T cells, B cells, NK cells, neutrophils, macrophages and dendritic cells.
Glycans are structures involved in many immunological processes. They covers the surfaces of all cells and they are added to protein and lipid backbones in the process called glycosylation. These molecules are recognized by variety of receptors presented or secreted by some of immunological system cells. Three the most significant receptors that recognize glycans has been described and these are galectins, C-type lectins and Siglecs.
Immunity can be defined as the ability of each living organism is Maintain its own integrity ( homeostasis ) through Recognizing the non -self and discriminating it from the self . In vertebrates innate and adaptive immunity mechanisms are Involved in fighting against Pathogens . According this general opinions , filogenetically older invertebrates respond this infection activating innate immunity reactions only .
Innate immunity is the first and in most organisms sole line of defence against pathogenic microorganisms. The activity of mechanisms of innate immunity starts with recognition of pathogen- associated molecular pattern (PAMP) by proteins that contain leucine rich repeats (LRR) domain. Plant proteins R contain TIR, NBD and LRR domains and recognize specifically fungal, bacterial or viral pathogens. After pathogen detection signal cascade is initiated that results in most cases with hypersen- sitive reaction in region of infection.