Changes

==Introduction==

==Introduction==

[[Image:LH Macrophage Histology.jpg|thumb|right|125px|<p>'''Macrophage'''</p>^{© Nottingham Uni}]]

[[Image:LH Macrophage Histology.jpg|thumb|right|200px|<p>'''Macrophage'''</p>^{© Nottingham Uni}]]

Pathogens can invade the body if a breach occurs in the barriers formed by the skin and mucus membranes, for example a wound, they must be detected and destroyed by cellular and [[Humoral Factors of Innate Immune System|humoral]] means.<br />

Pathogens can invade the body if a breach occurs in the barriers formed by the skin and mucus membranes, for example a wound, they must be detected and destroyed by cellular and [[Humoral Factors of Innate Immune System|humoral]] means.<br />

<br />

<br />

==[[Macrophages|Macrophages]]==

==[[Macrophages|Macrophages]]==

[[Image:Monocytes.jpg|thumb|right|150px|Monocytes - J. Bredl, RVC 2008]]

[[Image:Monocytes.jpg|thumb|right|200px|Monocytes - J. Bredl, RVC 2008]]

The innate cellular response begins with recognition and phagocytosis by macrophages that precide in the tissue where the wound occurs. The populations of distinct, tissue-specific macrophages that are present are the:

The innate cellular response begins with recognition and phagocytosis by macrophages that precide in the tissue where the wound occurs. The populations of distinct, tissue-specific macrophages that are present are the:

* Alveolar macrophages (lung)

* Alveolar macrophages (lung)

==[[Neutrophils|Neutrophils]]==

==[[Neutrophils|Neutrophils]]==

[[Image:Neutrophil 2.jpg|thumb|right|150px|Neutrophils - J. Bredl, RVC 2008]]

[[Image:Neutrophil 2.jpg|thumb|right|200px|Neutrophils - J. Bredl, RVC 2008]]

[[Neutrophils|Neutrophils]] are the principal, highly active '''[[Phagocytosis|phagocytes]]''' in the blood and comprise 30-70% of all white blood cells depending on species. Their main function is to kill and digest microbes in a similar way as macrophages. They also have another function of extracellular bacterial killing by disrupting bacterial membranes by the secretion of small antibacterial peptides, for example defensins and bactenecins.

[[Neutrophils|Neutrophils]] are the principal, highly active '''[[Phagocytosis|phagocytes]]''' in the blood and comprise 30-70% of all white blood cells depending on species. Their main function is to kill and digest microbes in a similar way as macrophages. They also have another function of extracellular bacterial killing by disrupting bacterial membranes by the secretion of small antibacterial peptides, for example defensins and bactenecins.

<br />

<br />

<br />

<br />

<br />

<br />

Their removal from the site after the removal of infection is an important step in the resolution of the lesion. Under physiological conditions the neutrophils undergo a process called '''apoptosis''' (or ''Programmed Cell Death''), and are then cleared by tissue macrophages ([[#Macrophages|see above]]). However, if there are too few macrophages to clear the cells, or the infection is resulting in the death of the neutrophils, they undergo a process called '''necrosis'''. When these neutrophils that have undergone necrosis accumulate at the site of infection it forms '''pus'''.

Their removal from the site after the removal of infection is an important step in the resolution of the lesion. Under physiological conditions the neutrophils undergo a process called '''apoptosis''' (or ''Programmed Cell Death''), and are then cleared by [[#Macrophages|tissue macrophages]] (see above). However, if there are too few macrophages to clear the cells, or the infection is resulting in the death of the neutrophils, they undergo a process called '''necrosis'''. When these neutrophils that have undergone necrosis accumulate at the site of infection it forms '''pus'''.

==[[Eosinophils|Eosinophils]]==

==[[Eosinophils|Eosinophils]]==

[[Image:Eosinophil.jpg|thumb|right|150px|Eosinophil - J. Bredl, RVC 2008]]

[[Image:Eosinophil.jpg|thumb|right|200px|Eosinophil - J. Bredl, RVC 2008]]

Eosinophils are less common than [[Neutrophils|neutrophils]], with eosinophils making up less than 5% of the leukocytes in normal blood. They are still described as granulocytes but they are not phagocytic.

Eosinophils are less common than [[Neutrophils|neutrophils]], with eosinophils making up less than 5% of the leukocytes in normal blood. They are still described as granulocytes but they are not phagocytic.

<br />

<br />

==[[Basophils|Basophils]] / [[Mast Cells|Mast Cells]]==

==[[Basophils|Basophils]] / [[Mast Cells|Mast Cells]]==

[[Image:Basophil and Lymphocyte.jpg|thumb|right|150px|Basophil - J. Bredl, RVC 2008]]

[[Image:Basophil and Lymphocyte.jpg|thumb|right|200px|Basophil - J. Bredl, RVC 2008]]

The basophils and the mast cells are principally localised at epithelial surfaces with very small numbers present in blood, making up less than 0.5% of circulating leukocytes.

The basophils and the mast cells are principally localised at epithelial surfaces with very small numbers present in blood, making up less than 0.5% of circulating leukocytes.

<br />

<br />

<br />

<br />

<br />

<br />

The first is the induction of [[:Category:Inflammation|acute inflammation]]. They do this through the production of '''[[Cytokines|cytokines]]''' by the mast cells in response to trauma and/or bacterial infection which then induces a classical acute inflammatory response.

The first is the induction of [[Acute Inflammation - Introduction|acute inflammation]]. They do this through the production of '''[[Cytokines|cytokines]]''' by the mast cells in response to trauma and/or bacterial infection which then induces a classical acute inflammatory response.

<br />

<br />

<br />

<br />

The second is to respond to parasite infection. They do this specifically by interacting with the Fc region of the [[Immunoglobulins|IgE]] class of antibody. When the IgE then comes into contact with antigen, Fc receptors on the surface of the Mast cells and basophils can interact with the antibody which causes the mast cells and basophils to degranulate. This causes the release enzymes and vasoactive substances that can result in a high level of mucus secretion and smooth muscle contraction. As the granules contain a much greater concentration of these peptides, the degranulation of Mast cells and Basophils creates a much more powerful response than that by neutrophils alone (it is for this reason that they can cause Type I hypersensitivity reactions). These cells also produce factors that influence local host cell physiology

The second is to respond to parasite infection. They do this specifically by interacting with the Fc region of the [[IgE|IgE]] class of antibody. When the IgE then comes into contact with antigen, Fc receptors on the surface of the mast cells and basophils can interact with the antibody which causes the mast cells and basophils to degranulate. This causes the release of enzymes and vasoactive substances that can result in a high level of mucus secretion and smooth muscle contraction. As the granules contain a much greater concentration of these peptides, the degranulation of mast cells and basophils creates a much more powerful response than that by neutrophils alone (it is for this reason that they can cause [[Type I Hypersensitivity|Type I hypersensitivity reactions]]). These cells also produce factors that influence local host cell physiology

and various mediators that increase the ratio of phagocyte to microbe (in particular [[Cytokines|cytokines]]).

and various mediators that increase the ratio of phagocyte to microbe (in particular [[Cytokines|cytokines]]).

<br><br>

<br><br>

{{Jim Bee 2007}}

{{Jim Bee 2007}}

[[Category:Innate Immune System]]

[[Category:Innate Immune System]]