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| − | ==Cellular responses== | + | ==[[Innate Immunity Cellular Responses]]== |
| − | [[Image:LH Macrophage Histology.jpg|thumb|right|125px|<p>'''Macrophage'''</p><sup>© Nottingham Uni</sup>]]
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| − | * If pathogens breach the barriers formed by the skin and mucus membranes, they must be detected and destroyed by cellular and humoral means
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| − | * The cells involved with innate protection are:
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| − | ** Blood granulocytes, or Polymorphonuclear Cells
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| − | *** Notable for their multi-lobed nuclei
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| − | *** '''Neutrophils''': phagocytose bacteria
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| − | *** '''Eosinophils''': kill parasites by the release of granules
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| − | *** '''Basophils/ mast cells''': kill parasites by the release of granules
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| − | ** Blood '''[[[[Monocytes|monocytes]]]]''': phagocytose bacteria
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| − | ** Tissue mast cells and '''macrophages''': phagocytose bacteria
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| − | *Effectively, innate cellular response seeks to hold off the infection until the [[Adaptive Immune System - WikiBlood|adaptive]] response can back it up with a more specific attack
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| − | ===[[Macrophages|Macrophages]]===
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| − | [[Image:Monocytes.jpg|thumb|right|150px|Monocytes - J. Bredl, RVC 2008]]
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| − | *The role of macrophages in Innate Immunity is to act as primary '''phagocytes'''
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| − | * Macrophages are present within tissues and take the form of distinct, tissue-specific populations:
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| − | ** Alveolar macrophages
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| − | ** Tissue histiocytes
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| − | ** Glomerular macrophages
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| − | ** Hepatic Küpffer cells
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| − | ** CNS microglia
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| − | ** Sinus-lining macrophages of the lymph nodes and spleen
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| − | * [[Monocytes|'''Monocytes''']] (immature macrophages) are circulating phagocytes
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| − | ** Circulate for 6-8 hours
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| − | ** Can function as phagocytes within the blood and as newly migrated cells in tissues
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| − | ** Chiefly function to replace the various tissue macrophage populations
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| − | ===[[Neutrophils|Neutrophils]]===
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| − | [[Image:Neutrophil 2.jpg|thumb|right|150px|Neutrophils - J. Bredl, RVC 2008]]
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| − | * Neutrophils are the principal, highly active '''phagocytes''' in the blood
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| − | ** Comprise 30-70% of white blood cells depending on species
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| − | ** Kill and digest microbes in a similar way as macrophages
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| − | * Neutrophils can also cause extracellular bacterial killing by disrupting bacterial membranes
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| − | ** Secrete small antibacterial peptides
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| − | *** E.g. defensins and bactenecins
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| − | * Neutrophils produce vasoactive peptides
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| − | ** E.g. histamine and bradykinin
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| − | ** Cause a great increase in extravasation of blood granulocytes and [[Monocytes|monocytes]] and plasma proteins at the site of infection
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| − | * Neutrophils are the archetypal cell associated with [[Inflammation - WikiBlood|acute inflammation]]
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| − | ** Are attracted to sites of inflammation by:
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| − | *** Complement activation
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| − | *** Cytokine production
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| − | *** Changes to vascular endothelium
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| − | ** Neutrophil activation in an inflammatory lesion results in the release of '''prostaglandins'''
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| − | *** Responsible for vasoactive changes and for pain
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| − | * The accumulation of dead and dying [[Neutrophils|neutrophils]] at the site of infection is called '''pus'''
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| − | ** Their removal from the site after the removal of infection is an important step in the resolution of the lesion
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| − | ===[[Eosinophils|Eosinophils]]===
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| − | [[Image:Eosinophil.jpg|thumb|right|150px|Eosinophil - J. Bredl, RVC 2008]]
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| − | * Eosinophils are less common than [[Neutrophils|neutrophils]], and they are not phagocytic
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| − | ** Make up <5% of the leukocytes in normal blood
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| − | * Eosinophil numbers are increased:
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| − | ** Slightly during the resolution phase of inflammation
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| − | ** Many-fold in parasite-infected animals
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| − | *** The presence of a large proportion of eosinophils in a blood smear is highly indicative of parasitaemia
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| − | * Mainly function by targeting the surface of parasites by means of specific antibody or complement
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| − | ** Release a large range of toxic molecules that break down the parasite integument
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| − | * Prominent in [[:Category:Allergic Diseases|allergic]] (anaphylactic) reactions
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| − | ===[[Basophils|Basophils]] / [[Mast Cells|Mast Cells]]===
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| − | [[Image:Basophil and Lymphocyte.jpg|thumb|right|150px|Basophil - J. Bredl, RVC 2008]]
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| − | * Basophils/mast cells are principally localised at epithelial surfaces
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| − | ** Very small numbers are present in blood
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| − | *** Less than 0.5% circulating leukocytes
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| − | * They have two principal functions:
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| − | *# Induction of [[Inflammation - WikiBlood|acute inflammation]]
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| − | *#* Trauma and/ or bacterial infection causes the production of '''cytokines''' by the mast cells that induce a classical acute inflammatory response
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| − | *# Response to parasite infection
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| − | *#* Specific [[Immunoglobulins|IgE]] binds cells
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| − | *#* Subsequent contact with antigen causes the mast cells to degranulate
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| − | *#* Release enzymes and vasoactive substances that can result in a high level of mucus secretion and smooth muscle contraction
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| − | * Also produce factors that influence local host cell physiology
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| − | ** Various mediators increase the ratio of phagocyte to microbe
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| | =Innate Immunity to Viruses= | | =Innate Immunity to Viruses= |