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Phagocytosis is the process of taking in particles such as bacteria, invasive fungi, parasites, dead host cells, and cellular and foreign debris by a cell. [22] It involves a chain of molecular processes.
The innate immune system is made of non-specific defensive mechanisms against foreign cells inside the host including skin as a physical barrier to entry, activation of the complement cascade to identify foreign bacteria and activate necessary cell responses, and white blood cells that remove foreign substances.
Bacterial cells are protected by a cell wall of polysaccharides, which are important virulence factors protecting bacterial cells against both immune host defenses and antibiotics. [57] To enter a host cell, bacteriophages bind to specific receptors on the surface of bacteria, including lipopolysaccharides , teichoic acids , proteins , or even ...
In a multicellular organism's immune system, phagocytosis is a major mechanism used to remove pathogens and cell debris. The ingested material is then digested in the phagosome. Bacteria, dead tissue cells, and small mineral particles are all examples of objects that may be phagocytized. Some protozoa use phagocytosis as means to obtain nutrients.
Cellular immunity protects the body through: T-cell mediated immunity or T-cell immunity: activating antigen-specific cytotoxic T cells that are able to induce apoptosis in body cells displaying epitopes of foreign antigen on their surface, such as virus-infected cells, cells with intracellular bacteria, and cancer cells displaying tumor antigens;
Macrophages (/ ˈ m æ k r oʊ f eɪ dʒ /; abbreviated Mφ, MΦ or MP) are a type of white blood cell of the innate immune system that engulf and digest pathogens, such as cancer cells, microbes, cellular debris, and foreign substances, which do not have proteins that are specific to healthy body cells on their surface.
Membrane attack complex (Terminal complement complex C5b-9) A membrane attack complex attached to a pathogenic cell The membrane attack complex (MAC) or terminal complement complex (TCC) is a complex of proteins typically formed on the surface of pathogen cell membranes as a result of the activation of the host's complement system, and as such is an effector of the immune system.
The B cell waits for a helper T cell (T H) to bind to the complex. This binding will activate the T H cell, which then releases cytokines that induce B cells to divide rapidly, making thousands of identical clones of the B cell. These daughter cells either become plasma cells or memory cells. The memory B cells remain inactive here; later, when ...