Cell-mediated immunity – Definition, Cells

Definition of Cell-Mediated Immunity The protective mechanism through which specialized immune cells, primarily T-cell lymphocytes and natural killer (NK) cells, carry out the immune response to protect the body from intracellular pathogens (diseasecausing entities, such as viruses and parasites, that invade the body’s cells). Cell-mediated immunity encompasses cytotoxic (death of invading cells) and phagocytic (consumption of cellular […]

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Leukotrienes – Definition

Leukotrienes Definition Molecules that instigate inflammation during an immune response. Mast cells secrete leukotrienes in response to stimulation by immunoglobulin E (IgE). Leukotrienes are derived from arachidonic acid, which is the same base source (precursor) as that of prostaglandins, the other primary agents of inflammation. The actions of leukotrienes are most apparent in asthma, in which they cause the bronchioles […]

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Vascular-Associated Lymphoid Tissue (VALT)

Vascular – Associated Lymphoid Tissue Definition Loosely collected clusters of lymph tissue throughout the inner, mucosal layer of the walls of the blood vessels. Researchers discovered VALT in the late 1990s and remain unsure of its role and functions. There do appear to be correlations between lymphocyte activity in VALT and cardiovascular conditions such as atherosclerosis, […]

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Chemokines – Definition and Cytokines

Definition of Chemokines Proteins, also called chemotactic cytokines, that draw or direct leukocytes to the scene of infection within the body. Macrophages produce chemokines when they encounter foreign cells, instigating an immune response. Some chemokines act as homing signals, marking the foreign cells so responding immune cells can zero in on them. Other send out biochemical “alerts” that attract circulating […]

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Lymphokines Definition and Cytokines

Lymphokines Definition Cytokines that convey biochemical messages among lymphocytes (a type of white blood cell) to direct their actions during an immune response. B-cell lymphocytes and T-cell lymphocytes both secrete lymphokines. Lymphokines activate and coordinate numerous immune functions across the spectrum of the immune response. They also stimulate cell growth and activation and stimulate macrophage activity. See also B-CELL LYMPHOCYTE; COMPLEMENT […]

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Clusters of Differentiation

Clusters of Differentiation Definition Clusters of differentiation – a system of classifying lymphocytes according to the collections of antigens on the surface of their cell membranes, also called CD markers. Each CD has a specific role in cell signaling and communication, guiding cell function and response. CDs are critical to the normal function of the immune system. […]

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Macrophage – Definition and Function

Macrophage Definition A monocyte that leaves the blood circulation and takes up residence in the tissues. Once there, the cell undergoes several changes: it greatly enlarges. it develops pseudopods (footlike projections) that permit it to move through tissue. it increases the amount of lysozyme its granules contain, increasing its ability to consume cellular debris. Macrophage Function Macrophages, […]

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Colony-stimulating factors (CSFs)

Colony-Stimulating Factors Definition Colony-Stimulating Factors are molecules that stimulate the growth of leukocytes (white blood cells) in the bone marrow. The body produces minute quantities of CSFs to regulate leukocyte production, maintaining the various types of leukocytes at appropriate levels to meet the needs of immune function. CSF production increases during infection and other demands for higher […]

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Mast Cell – Definition and Function

Mast Cell Definition Mast Cell – a granulated leukocyte that resides in tissues throughout the body. When the immune response stimulates mast cells, they release prostaglandins, histamine, and other biochemicals from their granules. Mast cells are primarily responsible for the symptoms that are the hallmark of the hypersensitivity reaction: inflammation, itching, skin rash, coughing, and sneezing. Mast cells have an […]

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Complement Cascade – Definition, Deficiencies

Complement Cascade Definition Complement Cascade is  the series of events that take place when an antibody binds with an antigen, activating the complements. Complements are proteins that participate in immune and inflammatory processes, acting primarily to kill antibody-marked cells. The biochemical interactions that take place with their activation ultimately lead to the formation of a protein structure called […]

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