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This cytokine—a class of signaling molecule [39] —kills cancer cells and cells infected by viruses, and helps to activate the other cells of the immune system. [ 40 ] In some diseases, e.g., the rare chronic granulomatous disease , the efficiency of phagocytes is impaired, and recurrent bacterial infections are a problem. [ 41 ]
This is a list of [[White blood cell|immune cell], also known as white blood cells, white cells, leukocytes, or leucocytes. They are cells involved in protecting the body against both infectious disease and foreign invaders .
Phagocytosis (from Ancient Greek φαγεῖν (phagein) 'to eat' and κύτος (kytos) 'cell') is the process by which a cell uses its plasma membrane to engulf a large particle (≥ 0.5 μm), giving rise to an internal compartment called the phagosome. It is one type of endocytosis. A cell that performs phagocytosis is called a phagocyte.
Ten toll-like receptors have been described in humans. [26] Cells in the innate immune system have pattern recognition receptors, which detect infection or cell damage, inside. Three major classes of these "cytosolic" receptors are NOD–like receptors, RIG (retinoic acid-inducible gene)-like receptors, and cytosolic DNA sensors. [27]
Humans are home to 10 13 to 10 14 bacteria, roughly equivalent to the number of human cells, [2] and while these bacteria can be pathogenic to their host most of them are mutually beneficial to both the host and bacteria. The human immune system consists of two main types of immunity: innate and adaptive.
T H 1 cells play an important role in classical macrophage activation as part of type 1 immune response against intracellular pathogens (such as intracellular bacteria) that can survive and replicate inside host cells, especially those pathogens that replicate even after being phagocytosed by macrophages. [45]
An immune response is a physiological reaction which occurs within an organism in the context of inflammation for the purpose of defending against exogenous factors. These include a wide variety of different toxins, viruses, intra- and extracellular bacteria, protozoa, helminths, and fungi which could cause serious problems to the health of the host organism if not cleared from the body.
The major functions of the innate immune system are to: recruit immune cells to infection sites by producing chemical factors, including chemical mediators called cytokines; activate the complement cascade to identify bacteria, activate cells, and promote clearance of antibody complexes or dead cells