WikiVet English - User contributions [en]

Eosinophils

2011-02-16T12:59:34Z

Kate English:

[[Image:LH Eosinophil Histology.jpg|thumb|right|150px|Eosinophil©RVC 2008]]

== Introduction ==

Eosinophils are a similar size to [[Neutrophils|neutrophils]], have a bilobed nucleus and are characterised by the large eosinophilic granules present in their cytoplasm. Produced in the [[Bone Marrow - Anatomy & Physiology|bone marrow]] they migrate into circulation briefly before moving into tissue where they survive for around six hours. The proportion of eosinophils circulating depends on the state of the animal. Normally numbers are very low but will rise considerably during a parasitic infection or allergic reaction.

Eosinophils are mainly located in connective tissue associated with routes into the animal i.e. the respiratory, alimentary, and urogential systems. They play key roles in reacting to [[Parasites|parasites]] and allergens but have limited phagocytic ability and therefore play no role in bacterial infections.

== Development ==

The eosinophil is a [[Blood Cells - Overview|granulocyte]] and has a similar development to the other granulocytes; this process is called [[Leukopoiesis#Granulopoiesis|granulopoiesis]]. Eosinophils differ morphologically in the size and density of the cytoplasmic granules between different animal species; the granules are more prominent in the pig and the horse.

== Granules ==

Two types of granules are present in eosinophils:

*Azurophilic granules which are present in all granulocytes and contain acid hydrolases and other enzymes.
*Specific granules contain four major proteins: Major basic protein (MBP) found in the crystalloid bodies, and then eosinophil cationic protein (ECP), eosinophil peroxidise (EPO) and eosinophil derived neurotoxin (EDN) which are all found in the granule matrix. Substances such as histaminases, cathepsins (proteases) and collagenases are also present.

== Actions ==

Eosinophils are involved in [[Type I Hypersensitivity|type I hypersensitivity]] reactions.

In an infection or allergic reaction, eosinophil numbers are increased by the release of [[Leukopoiesis#Eosinophils|Il-3, Il-5 and GM-CSF]] by Th2 and [[Mast Cells|mast cells]]. This causes more eosinophils to be released into the blood stream. The eosinophils are then attracted to the required site of action by chemicals known as eotaxins which are released by mast cells. Histamine and its breakdown products also act as attractants. These same products activate the eosinophil increasing its affinity to bind to [[IgE]].

Large numbers of eosinophils in a tissue give the tissue a greenish colour.

=== Anti-parasitic ===

FC receptors on eosinophils allow them bind to [[Parasites|parasites]] coated in antibodies and once bound they degranulate. The specific granules release EDN which interferes with the parasitic nervous system while MBP, ECP and EPO (EPO dissolves the carbohydrate coat of the parasite) all have anthelmintic and anti-[[Protozoa|protozoal]] actions. These proteins act as stimulants to mast cells causing them to release histamine and thus attracting more eosinophils. However, they also damage the animal’s tissue as well as the [[Parasites|parasites]].

=== Allergic ===

Histaminases in the specific granules breaks down histamine produced by mast cells while arylsulfatase breaks down leukotrienes. The products of these breakdowns further attracts more eosinophils.

=== In pathology ===

*See anti-parastic and allergic sections above
*Classically a cell involved in [[Acute Inflammation|acute inflammation]]
*Can be quite numerous in mast cell tumours of the skin of the dog
*[[Eosinophilia|Eosinophilia]]/[[Eosinopenia|Eosinopenia]]

 

[[Category:Blood_Cells]] [[Category:Kate_English_reviewing]]

Eosinophils

2011-02-16T12:58:44Z

Kate English:

[[Image:LH Eosinophil Histology.jpg|right|thumb|150px|'''Eosinophil'''©RVC 2008]]
==Introduction==
Eosinophils are a similar size to [[Neutrophils|neutrophils]], have a bilobed nucleus and are characterised by the large eosinophilic granules present in their cytoplasm. Produced in the [[Bone Marrow - Anatomy & Physiology|bone marrow]] they migrate into circulation briefly before moving into tissue where they survive for around six hours. The proportion of eosinophils circulating depends on the state of the animal. Normally numbers are very low but will rise considerably during a parasitic infection or allergic reaction.
Eosinophils are mainly located in connective tissue associated with routes into the animal i.e. the respiratory, alimentary, and urogential systems. They play key roles in reacting to [[Parasites|parasites]] and allergens but have limited phagocytic ability and therefore play no role in bacterial infections.

==Development==
The eosinophil is a [[Blood Cells - Overview|granulocyte]] and has a similar development to the other granulocytes; this process is called [[Leukopoiesis#Granulopoiesis|granulopoiesis]]. Eosinophils differ morphologically in the size and density of the cytoplasmic granules between different animal species; the granules are more prominent in the pig and the horse.

==Granules==
Two types of granules are present in eosinophils:
*Azurophilic granules which are present in all granulocytes and contain acid hydrolases and other enzymes.
*Specific granules contain four major proteins: Major basic protein (MBP) found in the crystalloid bodies, and then eosinophil cationic protein (ECP), eosinophil peroxidise (EPO) and eosinophil derived neurotoxin (EDN) which are all found in the granule matrix. Substances such as histaminases, cathepsins (proteases) and collagenases are also present.

==Actions==
Eosinophils are involved in [[Type I Hypersensitivity|type I hypersensitivity]] reactions.
In an infection or allergic reaction, eosinophil numbers are increased by the release of [[Leukopoiesis#Eosinophils|Il-3, Il-5 and GM-CSF]] by Th2 and [[Mast Cells|mast cells]]. This causes more eosinophils to be released into the blood stream. The eosinophils are then attracted to the required site of action by chemicals known as eotaxins which are released by mast cells. Histamine and its breakdown products also act as attractants. These same products activate the eosinophil increasing its affinity to bind to [[IgE]].
Large numbers of eosinophils in a tissue give the tissue a greenish colour.
===Anti-parasitic===
FC receptors on eosinophils allow them bind to [[Parasites|parasites]] coated in antibodies and once bound they degranulate. The specific granules release EDN which interferes with the parasitic nervous system while MBP, ECP and EPO (EPO dissolves the carbohydrate coat of the parasite) all have anthelmintic and anti-[[Protozoa|protozoal]] actions. These proteins act as stimulants to mast cells causing them to release histamine and thus attracting more eosinophils. However, they also damage the animal’s tissue as well as the [[Parasites|parasites]].

===Allergic===
Histaminases in the specific granules breaks down histamine produced by mast cells while arylsulfatase breaks down leukotrienes. The products of these breakdowns further attracts more eosinophils.
===In pathology===
*See anti-parastic and allergic sections above
*Classically a cell involved in [[Acute Inflammation|acute inflammation]]
*Can be quite numerous in mast cell tumours of the skin of the dog
*[[Eosinophilia|Eosinophilia]]/[[Eosinopenia|Eosinopenia]]
 
[[Category:Blood_Cells]] [[Category:Kate English reviewed]]

Category:Kate English reviewed

2011-02-16T12:58:18Z

Kate English: Created page with "Pages that Kate has reviewed"

Pages that Kate has reviewed

User:Kate English

2011-02-16T12:57:57Z

Kate English:

{{UserPage
|Name=Kate English
|Occupation= Veterinary Surgeon 
|School= UK - RVC (London)
|Year= 1999
|Email=
|Image=
}}
[[Category:UK - RVC (London) Graduates]]

[[:Category:Kate English reviewing|View pages]] that Kate is reviewing

Kate has reviewed [[:Category:Kate_English_reviewed|these pages]]

Category:Kate English reviewing

2011-02-16T12:57:19Z

Kate English: Replaced content with "Copy"

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Category:Kate English reviewing

2011-02-16T12:55:39Z

Kate English:

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[[Category:Kate English reviewed]]

Thrombocytes

2011-02-16T12:54:27Z

Kate English: /* Pathology */

{|align="right"
|<gallery>
Image:LH_Platelet_Histology.jpg|<center>'''Platelets'''©RVC 2008</center>
Image:LH_Avian_Thrombocyte_Histology.jpg|<center>'''Avian Thrombocytes'''©RVC 2008</center></gallery>
|}
Commonly known as '''''platelets
==Introduction==
Thrombocytes are small anuclear fragments of [[Thrombopoiesis#Megakaryocyte|megakaryocytes]]. They are membrane bound portions of the megakaryocyte cytoplasm and have a finely granular cytoplasm; they are much smaller than other blood cells at 2-3µm and have a lifespan of around 10 days in the circulation.

==Development==
[[Thrombopoiesis#Megakaryocyte|Megakaryocytes]] develop from [[Haematopoiesis - Overview#Colony Forming Units |CFU-GEMM]] and from these thrombocytes are formed during [[Thrombopoiesis|thrombopoiesis]].

==Structure==
[[Image:LH_Thrombocyte_TEM.jpg|thumb|150px|'''Transmission electron microscopy view of a Thrombocyte '''©Nottingham Uni 2008]]
The thrombocyte is structurally divided into four zones:
* ''Peripheral zone'' is the outer membrane with a coat of glycocalyx
* ''Structural zone'' contains microtubules and actin and myosin filaments
* ''Organelle zone'' contains organelles such as mitochondria along with three different granule types
* ''Membrane zone'' is made of of two types of membrane. One, the open canicular system, is membrane not used when the platelet budded off the megakaryocyte. The other, the dense tubular system, is membrane from the rough endoplasmic reticulum and is involved in calcium ion storage and regulation.
Reptilian thrombocytes are ellipsoidal to fusiform shaped with an elliptical, centrally positioned nucleus. They are similar in function to mammalian platelets and are involved in thrombus formation, blood clotting and wound healing.

[[Image:Thrombocyte.jpg|150px|thumb|right|'''Reptilian Thrombocytes''' (Copyright © RVC. All rights reserved)]]

==Granules==
*α granules are the most common and contain coagulation factors, fibrinogen, plasminogen, plasminogen activator factor and platelet derived growth factor (PDGF)
*δ granules contain ADP, ATP, serotonin and histamine and aid platelet adhesion and vasoconstriction
*λ granules contain lysosomes with hydrolytic enzymes to aid clot resorption

==Actions==
Thrombocytes play a number of roles in [[Normal_Mechanisms_of_Haemostatic_Control#Platelet_Responses|haemostasis]]. They adhere to exposed connective tissue in the walls of blood vessels forming platelet plugs, while releasing a number of factors from their granules. The glycocalyx on their surface provides a surface for fibrinogen to convert to fibrin leading to the formation of the secondary haemostatic plug. The platelets then contract (see structural zone) reducing the clot size. Finally lytic enzymes are released to break the clot down.If platelet numbers fall below 50x109/l an animal is likely to haemorrhage after trauma and if the count falls below 30x109/l then spontaneous haemorrhage is a risk.PDGF from the granules stimulates tissue repair in blood vessels by stimulating smooth muscle cell growth and division and by stimulating fibroblast activity.
===Pathology===
[[Category:Blood_Cells]] [[Category:Kate English reviewing]]

Neutrophils

2011-02-16T12:54:07Z

Kate English:

{| align="right"
|<gallery caption="Neutrophils" perrow="1">
Image:LH Neutrophil Histology Smaller.jpg|<div style="text-align: center;">'''Higher power'''©RVC 2008</div>
Image:LH Neutrophil Histology.jpg|<div style="text-align: center;">'''Lower power'''©RVC 2008</div>
Image:LH_Avian_Heterophils_Histology.jpg|<div style="text-align: center;">'''Avian Heterophil'''©RVC 2008</div>
</gallery>
|}
==Introduction==
Neutrophils represent up to half of all [[Leukocytes|leukocytes]] in the blood stream and are distinguished by their irregular multi-lobed nucleus and indistinct granular appearance. They are 10-12µm and circulate in the blood for minutes to hours (average 6-8 hours) and lasting for 1-2 days in tissue. Although the most abundant leukocyte in the blood the vast majority of neutrophils are found in the [[Bone Marrow - Anatomy & Physiology|bone marrow]] (5x more). Neutrophils play a key role during bacterial infections and have both phagocytic and killing actions.
Neutrophils are called '''heterophils''' in birds, reptiles and some mammals.

==Development==
The neutrophil is a [[Blood Cells - Overview|granulocyte]] and has a similar development to the other granulocytes; this process is called [[Leukopoiesis#Granulopoiesis|granulopoiesis]].

==Granules==
Three types of granules are present in neutrophils:
*Primary granules (azurophilic) are present in all [[Blood Cells - Overview|granulocytes]] and contain myeloperoxidase which creates anti-bacterial compounds, acid hydrolases and defensins.
*Secondary granules (specific) are the most numerous type and contain complement activators and enzymes e.g. collagenases.
*Finally tertiary granules are either phosphatases or metalloproteinases with the later aiding movement through connective tissue.

==Movement==
Neutrophils are extremely motile and express a number of adhesion molecules on their surface which allows them to attach to the walls of capillaries. 
Selection molecules expressed on the surface of neutrophil bind to receptors on the capillary endothelium causing a loose attachment. This allows the neutrophil to “roll” along the surface of capillaries. Stimulation by chemokines causes further attachment between the neutrophils intergrin molecules and associated receptors on the endothelium. Finally signalling molecules or [[Cytokines|cytokines]] such as tumour necrosis factors (TNF) and interleukin 1 (Il-1) cause the expression of inter-cellular adhesion molecule 1 (ICAM-1) and vascular cell adhesion molecule 1 (VCAM-1) on the neutrophil which causes firm attachment. 
The neutrophil then exhibits amoeboid movement and can pass through holes in the capillary wall that are smaller than themselves ('''diapedesis'''). This is achieved by extending a small part of the cell (a pseudopodium) through the capillary; the neutrophil's cytoplasm and contents then passes through. This process is assisted by the release of histamine and other vasodilators by other inflammatory cells.
Once within the tissue, neutrophils respond to chemotactic substances such as [[Cytokines|cytokines]] or bacterial products which attract the neutrophil to the area of damage/ infection. This process is called '''chemotaxis'''. Once neutrophils have entered tissue they do not return to the blood stream.

==Actions==
Neutrophils are the first inflammatory cells to enter damaged tissue from the blood after tissue damage has being caused. They are the predominant cell 4 - 6 hours after the beginning of an inflammatory reaction; at 12 hours there are also substantial numbers of [[Macrophages|macrophages]] and at 24 hours there are equal numbers of neutrophils and macrophages.
===Phagocytosis===
The main role of the neutrophil is to engulf and destroy foreign material. They uptake this material via endocytosis and this surrounds the material in the neutrophil membrane forming a '''phagosome'''. Lysosomes inside the neutrophil then fuse with the phagosome and release their contents degrading the foreign material. Phagocytosing material shortens the lifespan of the neutrophil due to the build up of toxins both from the degraded bacteria etc. and also from its own lysosomes contents. Most neutrophils die after phagocytosing 5-25 bacteria; sufficient numbers of dead neutrophils form [[Necrosis - Pathology#Pus Formation|pus]].
Neutrophils do not always destroy engulfed particles and may instead transport them to local lymph nodes to be dealt with by other host defence mechanisms. This means that acute inflammation in tissue can be accompanied by an acute inflammation in the lymph nodes.
====Recognition====
To function correctly neutrophils need to correctly identify material that is either foreign (non-self) or which requires removal, such as damaged cells. They are able to recognise some foreign material directly but in other circumstances proteins (opsonins) that bind to bacteria are required to increase the chances of successfully binding the foreign material to the neutrophil.

====Killing====
This occurs using either oxygen dependant pathways or oxygen independent pathways.
Oxygen dependant killing requires the production of reactive oxygen atoms that damage bacterial membranes. These atoms are generated during a burst of respiration following phagocytosis where increased amounts of oxygen are produced. Hydrochloric acid is also produced during this process.
Oxygen independent killing uses lysosomes, cathepsin (a protease) and other mechanisms. Lysozymes are particularly effective against gram positive bacteria as they hydrolyse the glycopeptide coating of the bacterial organisms.

===Interactions===
Il-6, Il-8 and C5a are all chemoattractants for neutrophils.
===In pathology===
*Classically a cell involved in [[Acute Inflammation|acute inflammation]]
*[[Necrosis - Pathology#Liquefactive Necrosis|Liquefactive necrosis]] in the formation of [[Necrosis - Pathology#Pus Formation|pus]]
*Are pyrogenic (fever producing)
*[[Neutrophilia|Neutrophilia]]/[[Neutropenia|Neutropenia]]
 

[[Category:Blood_Cells]] [[Category:Kate English reviewing]]

Monocytes

2011-02-16T12:53:32Z

Kate English: /* Monocytosis */

[[Image:LH Monocyte Histology.jpg|right|thumb|150px|'''Monocyte'''©RVC 2008]]
==Introduction==
Monocytes are the largest [[Leukocytes|leukocytes]]. They have a large indented nucleus, few granules and constitute about 5% of circulating leukocytes. Monocytes are precursors to a number of cells that make up the [[Lymphoreticular System - Anatomy & Physiology|mononuclear phagocytic system]]. Developing in the [[Bone Marrow - Anatomy & Physiology|bone marrow]], monocytes migrate into the circulation where, after approximately three days, they migrate into tissues and differentiate.

==Development==
Monocytes develop from the bi-potential [[Haematopoiesis - Overview#Colony Forming Units|CFU-GM]] stem cell during [[Leukopoiesis|leukopoiesis]].
When monocytes leave the blood stream they then differentiate into a number of cells (all are classified as [[Macrophages|macrophages]]):
* Connective tissue histiocyte
* [[Respiratory System General Introduction - Pathology#Alveolar macrophages|Alveolar macrophage]]
* Peritoneal macrophage
* Liver Kupffer cell
* Melanophage of skin
* Lipophage
* [[Bones - Anatomy & Physiology#Osteoclasts|Osteoclasts]] in bone
* [[Neurons_- Anatomy & Physiology#Microglial_Cells|Microglial cell]] in bone & brain
* Specialised histiocytes
** Epithelioid cell
* Histiocytic giant cell
** Langerhans cell
** Touton giant cell
[[Image:Monocyte Picture.jpg|thumb|right|150px|Monocyte Picture - Copyright Prof Dirk Werling DrMedVet PhD MRCVS]]

==Action==
During inflammation chemokines attract monocytes which migrate out of blood vessels into the damaged tissue, where they differentiate into cells of the [[Lymphoreticular System - Anatomy & Physiology|mononuclear phagocytic system]].
Monocytes can live for months to years in the circulation.
Monocytes are referred to as macrophages once they enter a tissue by '''diapedesis'''.
Monocytes/macrophages act as phagocytes, removing particular antigens. They also act as antigen presenting cells to take up, process and present antigen to [[T cells]].
==Monocytosis==
An increase in the number of monocytes (haematogenous macrophages) in the blood is known as a [[Monocytosis|monocytosis]]. It occurs in conjunction with other changes inidicative of a [[Stress Leucogram|stress leucogram]] or it may occur independently. Monocytes in the blood represent a brief transitional stage as they quickly move into tissues and differentiate further to tissue macrophages; they rarely perform any notable functions whilst in the bloodstream but they have been found to phagocytose red blood cells in cases of immune-mediated haemolytic anaemia. The major causes of monocytosis are:
*Stress leucogram mediated by the production or administration of glucocorticoids (plus a neutrophilia, eosinopenia and lymphopenia).
*Chronic inflammatory processes, including chronic bacterial infections and chronic inflammatory diseases of the liver (chronic hepatitis and cholangitis) and pancreas (chronic pancreatitis).
*Granulomatous disease results in monocytosis as monocytes are recruited to contain certain types of bacteria (namely Mycobacteria spp., Nocardia spp., Actinomyces and Rhodococcus equi) or foreign bodies.
*Certain types of monocytic or myelomonocytic chronic myeloid leukaemia may result in the presence of large numbers of monocytes in the blood.

[[Category:Blood_Cells]] [[Category:Kate English reviewing]]

Mast Cells

2011-02-16T12:53:03Z

Kate English:

[[Image:LH Mast cell Histology.jpg|right|thumb|150px|'''Mast cell'''©Nottingham Uni 2008]]
[[Image:LH Mast cells Histology.jpg|right|thumb|150px|'''Mast cells'''©Nottingham Uni 2008]]
==Introduction==
Mast cells are derived from the same stem cell line as [[Basophils|basophils]] and while they are similar to basophils they are not identical. Mast cells are found in connective tissue and are larger than other [[Leukocytes|leukocytes]] at 15-20µm. They have cytoplasm containing a high number of large, intensely staining basophilic granules which mask the nucleus.
==Development==
Mast cells colony forming units (CFU) develop in the [[Bone Marrow - Anatomy & Physiology|bone marrow]] from the myeloid set cell ([[Haematopoiesis - Overview#Colony Forming Units|CFU-GEMM]]) under the stimulation of IL-3 and Stem Cell Factor. Then under the stimulation of Il-6 and SCF the immature mast cells are formed. These then enter circulation where they remain undifferentiated. On migration into tissue they then differentiate, under stimulation by Il-4, and produce their granules. Once in the tissue mast cells may last for weeks to months.

==Granules==
Mast cells can be classified by the presence or lack of tryptase and/or chymase. MCTC mast cells have granules that contain tryptase and chymase (found mainly in skin and intestinal submucosa) while MCT mast cells have granules containing only tryptase (found mainly in respiratory tissue and intestinal mucosa). They can also be classified by their location within the body<ref>{{citation|initiallast = Metcalfe|initialfirst = D.D|2last = Baram|2first = D|finallast = Mekori|finalfirst = Y|year = 1997|jtitle = Mast Cells|jor = Physiological Reviews|vol = 77(4)|range = 1033-1064}}</ref>. Mast cells in connective tissue are larger, have the proteoglycan heparin and contain high amounts of histamine while mucosal mast cells contain less histamine and have the proteoglycan chondroitin sulphate.More generally the granules contain:
* Preformed mediators such as serotonin, histamine, proteoglycans, heparin and serine proteases (tryptase and/or chymase)
* Lipid mediators such as leukotrienes and prostaglandin D2
* Cytokines: Il-3, Il-4, Il-5, Il-6, Il-8, Il-13, Il-16 TNF-α
*Chemotactic factors for both [[Neutrophils|neutrophils]] and [[Eosinophils|eosinophils]]
Histamine increases vascular permeability, mucous production and smooth muscle tone in the respiratory tract and is responsible for the itch sensation in the skin. Heparin is an anticoagulant and binds with antithrombin III and platelet factor IV to block coagulation factors. Leukotrienes like histamine are responsible for contraction of respiratory smooth muscle. Chymase plays a role in the production of angiotensin II.
Mast Cell granules are thought to produce a ground substance to facilitate collagen formation which occurs during the repair of an injury.

==Actions==
Mast cells are involved in the inflammatory response and play a key part in anaphylaxis.
[[IgE]] released by plasma cells in response to antigens bind to FC receptors on the mast cell surface. This stimulates the mast cells to degranulate. The granule contents cause blood vessel permeability to increase and, along with chemotactic factors, this enhances the migration of other leukocytes to the area. The production of angiotensin II by chymase causes systemic vasoconstriction in response to vascular damage.

==In pathology==
*Classically a cell involved in [[Acute Inflammation|acute inflammation]]
*[[Neoplasia_-_Pathology#Mast_Cell_Proliferation_Disorders|Mast cell tumours]] of the intestine, liver and skin.

==References==
<references />
 

[[Category:Blood_Cells]] [[Category:Kate English reviewing]]

Macrophages

2011-02-16T12:52:29Z

Kate English:

[[Image:LH Macrophage Histology.jpg|thumb|right|125px|'''Macrophage'''© Nottingham Uni]]
==Introduction==
Macrophages are large, round cells that contain a central round nucleus and have abundant clear, often vacuolated, cytoplasm. Macrophages acts as sentinel cells; they have a role in destroying bacteria, protozoa and tumour cells, and release substances that act upon other immune cells. Macrophages are phagocytic, long lived and are found throughout the body.

==Development==
Macrophages are either derived from blood borne [[Monocytes|monocytes]] which have migrated into tissue and differentiated, or from dividing macrophages within the tissue.
===Locations===
Macrophages are present throughout the body with large numbers in the [[Lymph Nodes - Anatomy & Physiology|lymph nodes]], [[Bone Marrow - Anatomy & Physiology|bone marrow]] and [[Spleen - Anatomy & Physiology|spleen]]. In connective tissue macrophages are fixed and referred to as tissue histocytes. Sentinel macrophages in the lung are called alveolar macrophages, while in the [[Liver - Anatomy & Physiology|liver]] they are called Kupffer cells. In the brain they are microglia with long cytoplasmic processes.

===Variations===
====Epithelioid cells====
* Look like squamous epithelial cells with a pink (eosinophilic) cytoplasm and indistinct borders.
* May be binucleate.
* Tend to remain in the lesion.
* It is thought by some people that they may not phagocytose, but instead secrete substances directed against the foreign agent.

====Giant cells====
Macrophages can fuse together to form giant cells (Langhan’s cells), which with their greater cytoplasmic volume and number of lysosomes are able to engulf and deal with large foreign particles/bodies. They are thought to form when two or more macrophages attempt to engulf the same organism; the resulting cell can contain between two to several hundred nuclei per cell).The nuclei can be scattered throughout the cytoplasm, clumped in the centre in foreign body granulomas or appear in a horseshoe shape at the periphery of the cytoplasm at one end in tuberculosis and some other granulomas. In the past, the morphology of these giant cells was correlated with the agent responsible for inflammation, although the distinction is not absolute.

==Actions==
Macrophages are phagocytic and take up particles and cell debris by endocytosis, as well has engulfing pathogens like bacteria. These are then present in the macrophage inside phagosomes. Lysosomes present in the cytoplasm then bind with the phagosome and release their contents which degrade/digest its contents.
Macrophages also act as '''antigen presenting cells''' taking antigens to lymph nodes to present to T cells. MHC II ([[Major Histocompatability Complexes|major histocompatibility complex]] II) proteins on their surface allow them to interact with helper T cells (CD4). Short peptide segments from foreign cells are presented with MHC II which activates the [[T cells|T cell]].
To migrate through connective tissue they release proteases and glycoaminoglycanases.
===Role in pathology===
Macrophages are seen in both [[Acute Inflammation|acute]] and [[Chronic Inflammation| chronic inflammation]]. If large numbers of macrophages are found in chronic inflammatory processes, it implies the inability to eliminate the causal organism e.g. [[:Category:Mycobacterium species|Mycobacterium (TB)]], [[:Category:Actinobacillus species|Actinobacillus]], fungi, parasites and foreign bodies.
 
[[Category:Blood_Cells]] [[Category:Kate English reviewing]]

User:Kate English

2011-02-16T12:51:53Z

Kate English:

Erythrocytes

2011-02-16T12:51:12Z

Kate English:

[[Image:LH Erythrocyte Histology.jpg|thumb|right|150px|'''Erythrocytes''' ©RVC 2008]]
Also known as '''''red blood cells (RBCs)
Erythrocytes deliver oxygen to, and remove carbon dioxide from tissues.
==Development==
Erythrocytes are derived from the stem cell ([[Haematopoiesis - Overview#Colony Forming Units|CFU-GEMM]]) and formed in a process known as [[Erythropoiesis|erythropoiesis]].
==Erythrocyte Structure==
[[Image:LH_Avian_Erythrocyte_Histology.jpg|thumb|right|150px|'''Avian Erythrocytes'''.©RVC 2008]]
===Mammals===
Erythrocytes are small (4-8µm), circular, anucleate biconcave cells that lack organelles. 
The cell's membrane is a lipid bilayer which contains two different protein groups. Integral membrane proteins, which make up most of the proteins, and peripheral membrane proteins. The arrangement of these proteins makes the membrane elastic but stable and contributes towards the biconcave shape.
The biconcave shape increases the cell's surface area by 20-30%, thereby increasing the probability of oxygen binding with the haemoglobin molecule within the RBC.

===Birds===
In birds erythrocytes are ovoid and contain a nucleus.

==Function==
RBCs contain haemoglobin, an oxygen binding protein that is responsible for the transport of oxygen from the lungs to tissues, and the transportation of carbon dioxide from the tissues to the lungs for elimination.
[[Image:LH Hb Animation.gif|thumb|right|250px|Blue(α) & orange(β) are globin chainsRed objects represent haem groups]]
Haemoglobin (Hb) is a metalloprotein that binds oxygen reversibly and accounts for almost all of the protein in the erythrocyte.
When bound to oxygen it is referred to as oxyhaemoglobin and when unbound, deoxyhaemoglobin. Haem gives blood its colour, and this colour depends on its saturation. When fully saturated with four oxygen molecules it appears red and when completely unsaturated it appears blue-red.
Haemoglobin also acts as an extracellular buffer
*Hb(O2)H + H2 ↔ Hb(O2)- + H3O+
**pKa = 6.6
*HbH + H2O ↔ Hb- + H3O+
**pKa = 7.8

====Haemoglobin Structure====
Haemoglobin is composed of globin and four haem groups which contain an iron atom in each haem group. Four oxygen molecules can bind to each haemoglobin - one to each heam group via the iron when in its ferrous state.
=====Globin=====
Globin is composed of two polypeptide groups each composed of two polpeptides chains. The chains are identical within the group, but differ between the groups. Globin varies between species and individuals within a species due to changes in the polypeptide chain sequence.
=====Haem=====
Each of the haem groups has an iron atom at its centre and each iron atom binds one molecule of oxygen. Haem groups are identical in all species.

====Types====
 There are three types of haemoglobin: embryonic, foetal and adult. Embryonic is present in the early stages of foetal development. Foetal haemoglobin has a higher affinity for oxygen than adult haemoglobin and is replaced by adult haemoglobin shortly after birth. Dogs do not have foetal or embryonic haemoglobin. Horses do not have embryonic haemoglobin and their foetal haemoglobin is structurally identical to adult haemoglobin and as such some would say that there is no foetal haemoglobin. Pig (and horse) foetal haemoglobin has the same affinity for oxygen as their adult haemoglobin.

====Chemistry====

*One gram of haemoglobin binds 1.34g of oxygen.
*Haemoglobin concentration (g/l) varies between species
**Poultry: 90
**Ruminants: 100-120
**Dogs: 150

===Antigens===
The RBC surface contains glycoproteins that are specific to the individual and potentially antigenic. Plasma contains antibody like substances known as agglutins - mixing RBCs with the blood of another individual can create an agglutination reaction where the plasma agglutins and the RBC glycoproteins bind together. This is the basis of a transfusion reaction and other blood type abnormalities associated with reproduction such as [[Neonatal Isoerythrolysis|neonatal isoerythrolysis]] in horses and fading kitten syndrome.

==Degradation==
Erythrocytes have a limited life span and as they age their membranes become more fragile leading to a loss of function and swelling. Damage occurs as the fragile cells pass through narrow capillaries which occurs particularly in the [[Spleen - Anatomy & Physiology#Erythrocytes & Platelets|spleen]]. Ageing also causes sialic acid to be lost from the membrane and this exposes galactose moieties leading to phagocytosis.
===Life Span===
The life span of the erythrocyte varies from 70-160 days in domestic species although the life span is often shorter in juvenile animals (e.g. calves and lambs) compared to adult animals. Erythrocytes in small animals have a shorter life span than in the larger domestic species.
{| border="0" cellpadding="5" cellspacing="1"
!style="color:black;background-color:#FFC1C1;" colspan="7"|Life span (days)
|-
! <div style="text-align: center;">Cat</div>
! <div style="text-align: center;">Pig</div>
! <div style="text-align: center;">Dog</div>
! <div style="text-align: center;">Goat</div>
! <div style="text-align: center;">Horse</div>
! <div style="text-align: center;">Sheep</div>
! <div style="text-align: center;">Cattle</div>
|-
| <div style="text-align: center;">70</div>
| <div style="text-align: center;">85</div>
| <div style="text-align: center;">120 </div>
| <div style="text-align: center;">125 </div>
| <div style="text-align: center;">145</div>
| <div style="text-align: center;">150</div>
| <div style="text-align: center;">160</div>
|}
''Transfused dog erythrocytes last around 21 days''

===Breakdown===
Around 90% of erythrocytes are phagocytised by [[Macrophages|macrophages]] in the [[Liver - Anatomy & Physiology|liver]], [[Spleen - Anatomy & Physiology|spleen]] and [[Bone Marrow - Anatomy & Physiology|bone marrow]], with the other 10% breaking down in circulation.

Following phagocytosis, haemoglobin is broken down into haem and globin. Globin, a protein, is hydrolysed into amino acids while the haem is transformed into biliverdin and then into bilirubin before being excreted into the blood stream bound to albumin. In the [[Liver - Anatomy & Physiology|liver]] it is conjugated and excreted into bile which in turn is excreted into the [[Alimentary System Overview - Anatomy & Physiology#Stomach|gastro-intestinal system]]. The iron from haem is either stored as insoluble ferritin in the [[Liver - Anatomy & Physiology|liver]] (in hepatocytes and [[Macrophages|macrophages]]) or it is directly transported to the [[Bone Marrow - Anatomy & Physiology|bone marrow]] for reuse in [[Erythropoiesis|erythropoiesis]].
[[Image:Haem Breakdown.jpg|center|thumb|375px|<div style="text-align: center;">'''Haem breakdown pathway'''©Nottingham Uni 2008</div>]]
 
[[Category:Blood Cells]] [[Category:Kate English reviewing]]

Eosinophils

2011-02-16T12:50:44Z

Kate English:

Category:Kate English reviewing

2011-02-16T12:44:14Z

Kate English: Created page with "test"

test

Basophils

2011-02-16T12:44:04Z

Kate English:

[[Image:LH Basophil Histology.jpg|thumb|right|150px|Basophil©RVC 2008]] [[Image:LH Avian Basophil Histology.jpg|thumb|right|150px|Avian Basophil©RVC 2008]]

== Introduction ==

Basophils are derived from the same stem cell line as [[Mast Cells|mast cells]] and while they are similar to mast cells, they are not identical (they are thought by some to be immature mast cells). They are the least common of all the [[Leukocytes|leukocytes]], are a similar size to neutrophils and eosinophils and are characterised by the large number of basophilic staining granules in their cytoplasm. They are present in the circulation but rarely found in tissue.

== Development ==

The basophil is a [[Blood Cells - Overview|granulocyte]] and has a similar development to the other granulocytes. This process is called [[Leukopoiesis#Granulopoiesis|granulopoiesis]].

== Granules ==

Two types of granules are present in basophils:

*Azurophilic granules which are present in all granulocytes and contain acid hydrolases and other enzymes.
*Specific granules contain heparin, histamine, leukotrienes and some lysosomes. Heparin has anti-coagulative capabilities and is also involved in assisting lipid uptake from the blood after meals. Histamine causes vasodilation.

== Actions ==

Fc receptors on the basophil surface binds with IgE formed during allergic reactions and causes them to degranulate. The vasoactive substances released from the granules causes vasodialtion allowing for the infiltration of other leukocytes i.e. [[Neutrophils#Movement|neutrophil diapedesis]].

=== Role in pathology ===

*Classically a cell involved in [[Acute Inflammation|acute inflammation]]

== Interactions ==

*[[IgE]] and CD40 receptors on the basophils interact with B cells to increase [[IgE]] production
*Il-8 released by [[Neutrophils|neutrophils]] attracts basophils
*[[Complement]] factor C3a binds to the basophil and causes degranulation

 

[[Category:Blood_Cells]] [[Category:Kate English reviewing]]