Download Functions Of White Blood Cells Monocyte

Functions Of White Blood Cells
Monocyte-Macrophage System (RETICULOENDOTHELIAL SYSTEM)
LEARNING OBJECTIVES
At the end of the lecture, the student will be able to :
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Describe the functions of Leucocytes.
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What makes the hallmark of acute inflammation.
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Give the role of neutrophils, eosinophils, basophils, monocytes and macrophages
in the immune system.
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Describe the components of the monocyte macrophage system.
WHITE BLOOD CELLS
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Granulocytes
(polymorponuclear leukocytes) include:
neutrophils, basophils, and eosinophils.
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Agranulocytes
(mononuclear leucocytes):
include: lymphocytes, monocytes, and macrophages.
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FUNCTIONS OF WHITE BLOOD CELLS
Leukocytes are fighting forces in the human body.
Eosinophils deal with parasitic infections.
Basophils responsible for allergic response .
Neutrophils defend us from bacteria and fungus.
Lymphocytes common in lymphatic system.
Monocytes are pieces of pathogens to T cells so that the
„bad“ cells could be recognized and killed. They leave the blood to become
macrophages (they allow a process called phagocytosis).
ROLE OF NEUTROPHILS
Form an essential part of innate immune system.
recruited to site of injury within minutes following trauma.
hallmark of acute
inflammation.
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Undergo chemotaxis.
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Cell surface receptor
allow neutrophils to
detect chemical
gradients of molecules such as interleukin-8 (IL-8), interferon
gamma (IFN-gamma), and C5a, which these cells use to direct
the path of their migration.
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ROLE OF NEUTROPHILS (CONT.)
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Being highly motile, neutrophils quickly congregate at a focus of infection, attracted
by cytokines expressed by activated endothelium, mast cells, and macrophages.
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Neutrophils express and release cytokines, which in turn amplify inflammatory
reactions by several other cell types.
Have three strategies for directly attacking micro-organisms :
1.Phagocytosis (ingestion).
2.Release of soluble anti-microbials (including granule proteins)
3.Generation of neutrophil extracellular traps (NETs)
PHAGOCYTOSIS:
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Internalize and kill many microbes, each phagocytic event resulting in the
formation of a phagosome into which reactive oxygen species and hydrolytic
enzymes are secreted
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The consumption of oxygen during the generation of reactive oxygen species has
been termed the "respiratory burst”
Degranulation:
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Neutrophils also release an assortment of proteins in three types of granules
by a process called degranulation.8
Have three types of granules:
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Specific granules (or "secondary granules").
Azurophilic granules (or "primary granules").
Tertiary granules.
NEUTROPHIL EXTRACELLULAR TRAPS NETS
Activation of neutrophils causes the release of web-like structures of DNA !
These neutrophil extracellular traps (NETs) comprise a web of
fibers composed of chromatin and serine proteases that trap and
kill microbes extracellularly .
Recently discovered mechanism of neutrophil killing.
ROLE OF BASOPHILS
Basophils appear in specific kinds of inflammatory reactions,
particularly those that cause allergic symptoms
Basophils contain anticoagulant heparin.
contain vasodilator histamine.
They can be found in unusually high numbers at sites of ectoparasite infection,
e.g., ticks.
Like eosinophils, basophils play a role in both parasitic infections
and allergies
Basophils have protein receptors on their cell surface that bind
IgE, an immunoglobulin involved in macroparasite defense and
allergy.
ROLE OF EOSINOPHILS
Following activation, eosinophils effector functions include production of:
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cationic granule proteins and their release by degranulation
Reactive oxygen species such as superoxide, peroxide, and hypobromite.
Lipid mediators like the eicosanoids from the leukotriene and prostaglandin (e.g.,
PGE2) families. enzymes, such as elastase.
Growth factors such as TGF beta, VEGF, and PDGF
Cytokines such as IL-1, IL-2, IL-4, IL-5, IL-6, IL-8, IL-13, and TNF alpha
ROLE OF MONOCYTES
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Monocytes have two main functions in the immune system:
(1) Replenish resident macrophages and dendritic cells under normal states
(2) In response to inflammation signals, monocytes can move quickly (approx. 8-12
hours) to sites of infection in the tissues and divide/differentiate into macrophages
and dendritic cells to elicit an immune response.
Half of them are stored in the spleen.
ROLE OF MACROPHAGES
Three important roles :
1.Phagocytosis.
2.Antigen presentation.
3.Muscle regeneration.
RETICULOENDOTHELIAL SYSTEM
Also called as Mononuclear phagocytic system and lympho
reticular system
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The total combination of monocytes, mobile macrophages, fixed tissue
macrophages, and a few specialized endothelial cells in the bone marrow, spleen,
and lymph nodes is called the reticuloendothelial system
COMPONENTS OF RES
Basically it is formed by two different types of tissues:
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Primary Lymphoid organs.
Secondary Lymphoid organs.
PRIMARY LYMPHOID ORGANS
Include all those organs where the cells of RES are formed and get
matured
Includes :
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Bone Marrow
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Thymus
Secondary lymphoid organs
Includes the sites where the cells of RES function:
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Lymph nodes
Tonsils
Spleen
MALT (mucosa associated lymphoid tissue)
Others ( kupfer cells , Microglia etc.)
MALT
MALT is further divided into:
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BALT (Bronchus associated Lymphoid tissue)
GALT (Gut associated lymphoid tissue)
NALT (nose-associated lymphoid tissue)
LALT (larynx-associated lymphoid tissue)
SALT (skin-associated lymphoid tissue)
VALT (vascular-associated lymphoid tissue. A newly recognized entity that
exists inside arteries; its role in the immune response is unknown.)
CALT (conjunctiva-associated lymphoid tissue in the human eye)
MACROPHAGES IN LYMPH NODES
Can be regarded as CHECK POSTS of the body
All the particles including microorganisms after invasion of tissues donot enter
directly in the blood
Instead they enter the lymph and are then trapped in the nodes in the sinusoids
lined by the tissue macrophages
MACROPHAGES IN SPLEEN AND BONE MARROW
If the organism has been successful in passing through the lymph nodes , then its
enters the blood !
But it has another obstacle to encounter THE SPLEEN
The spleen is similar to the lymph nodes, except that blood, instead of lymph, flows
through the tissue spaces of the spleen.
The red pulp and the venous sinuses in the spleen are lined by macrophages
where they are active in removing the invading organism as well as unwanted
debris in the blood, like old and distorted RBCs
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MACROPHAGES IN TONSILS
Four groups of tonsils in pharyngeal region provides effective
defense mechanism against intruders trying to enter body via
nose and mouth.
They all form Waldeyer's tonsillar ring.
Have got the same function as that of lymph nodes as they too
have the macrophages lining their interior.
MALT
MALT is populated by lymphocytes such as T cells & B cells,
as well as plasma cells and macrophages, each of which is
well situated to encounter antigens passing through mucosal
epithelium
In case of intestinal MALT, M cells are also present, which
sample antigen from lumen and deliver it to lymphoid tissue.
GALT (GUT ASSOCIATED LYMPHOID TISSUE)
Immune system of GIT.
Comprises 70% of body’s immune system.
GALT is made up of several types of lymphoid tissue that store immune cells, such
as T and B lymphocytes, that carry out attacks and defend against pathogens.
Payer’s patches ,found in the small intestine , mostly in the ileum ,are part of GALT
GALT may continue to be a major site of HIV activity, even if drug treatment has
reduced HIV count in the peripheral blood.
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MACROPHAGES IN TISSUES AND SUBCUTANEOUS TISSUES
Also called as HISTIOCYTES.
derived from circulating monocytes that have become
lodged in tissues and subcutaneous tissues.
Provide first line of defense if the skin gets interupted
because of some damage to epithelium.
MACROPHAGES IN LUNGS
Alveolar Macrophages
Large numbers of tissue
macrophages are present as integral
components of the alveolar walls.
Two fates of the entering organism:
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If particles are digestible, macrophages can also digest them
and release digestive products into the lymph.
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If particle is not digestible, macrophages often form a “giant
cell” capsule around the particle until such time—if ever—that
it can be slowly dissolved.
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MACROPHAGES IN LIVER SINUSOIDS
Also called as KUPPFER cells.
If organism entering through GIT has been able to enter GALT
in submucosa of intestinal tract , then it is carried all the way
through portal circulation to sinusoids of liver where tissue
macrophages are present.
Effectively remove ALL the invading organisms ,thus none of
them is able to enter the blood stream
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MACROPHAGES IN BRAIN
MICROGLIA of the Central Nervous System can be considered
a part of reticuloendothelial system.
They are scavenger cells that proliferate in response to CNS
injury.
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