Immunity Biology 2122 Chapter 21. Introduction Innate or nonspecific defense: – First-line of...
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Transcript of Immunity Biology 2122 Chapter 21. Introduction Innate or nonspecific defense: – First-line of...
Immunity
Biology 2122Chapter 21
Introduction
• Innate or nonspecific defense: – First-line of defense– Second-line of defense
• The adaptive or specific defense system– lymphocytes, the production of antibodies specific to certain
antigens
• The immune system is a ‘functional’ system
Innate Defense System Epidermis and keratin-cells provide a tough barrier to penetrate
▫Resistant to weak acids, bases, toxins
The mucous membranes • physical barrier
▫3-5 pH ▫HCl in the stomach (pH 2)▫Saliva contains lysozyme ▫Mucus
Internal Defense If the surface defenses are broken, microorganisms will invade deeper tissue areas.
Nonspecific cells and chemicals – prevent the ‘invaders’ from penetrating deeper into the body
Cells involved- Nonspecific Cells:– 1. Phagocytes- Neutrophils, Eosinophils– 2. Natural Killer Cells– 3. Mast cells
•When body tissues are damaged– inflammatory response is set into motion which involves a series of chemicals
The Role of Phagocytes Monocytes will leave the bloodstream and be converted into the ‘main’ phagocytes called macrophages.
They can be free (lungs) or fixed in position (Kupffer cells in the liver)
Other WBCs involved: – 1. Neutrophils – 2. Eosinophils – 3. Mast cells
Phagocytosis– Phagosome– Phagolysosome – Opsonization – Respiratory Burst
– Animation
Natural Killer Cells
Large granular lymphocytes - non-specific• Detect ‘non-self’ cells via the surface receptors.• Eliminate cancerous or infected cells.• The mode of killing is via the release of cytolytic chemicals
called perforins• Not Phagocytic
What is an ‘inflammatory’ response?
When tissues are injured– ‘healing process’ that eliminates debris and pathogens in the
affected area. – Identifiable signs of an inflammation are redness, heat,
swelling and pain.
•Macrophages have surface membrane receptors called Toll-like Receptors or TLRs.
▫ If activated, TLR triggers the release of chemicals called cytokines that cause inflammation and attract WBCs to the site of the injury
Inflammatory Chemicals Histamines
• released by basophils and mast cells, microorganism or chemicals released by neutrophils
• Promotes vasodilation; permeability of capillaries
Kinins • produced from the cleavage of a plasma protein called
kiniogen • Induces chemotaxis of leukocytes; same roles as histamine
Prostaglandins or PGs – fatty acid molecules – generated by lysosomal enzymes of neutrophils and other
cells– Production of free radicals
Inflammatory Chemicals - Effects
Most of the chemicals: 1. ‘Vasodilation’ of blood vessels
2. Increases the permeability of capillaries causing fluid to leak out into the extracellular space• exudate fluid and contains clotting factors and
antibodies
3. Causes swelling (edema), which causes pressure on nerves, results in pain• Dilutes harmful substances; brings oxygen and nutrients;
entrance of clotting proteins
Inflammatory Response
1. Release of Chemical Mediators
2. Vasodilation, increased permeability of capillaries
3. Attraction of neutrophils, monocytes, leukocytes, “chemotaxis”
4. Vasodilation leads to “hyperemia”, redness swelling
5. Capillary permeability leads to exudate, pain, swelling, clotting Leukocytes migrate ----- Margination ---- Diapedesis
----- Phagocytosis of dead tissue and cells, etc.
Phagocyte Mobilization
Neutrophils are first followed by macrophages
1. Leukocytosis – injured cells release leukocytosis inducing factors which promote the fast release of neutrophils from red marrow.
2. Margination – Blood flow slows in the injured region and the neutrophils will attach to CAMs called selectins on the endothelial cells.
3. Diapedesis – Neutrophils are able to squeeze through the walls
4. Chemotaxis – chemotactic agents (inflammatory chemicals) attract neutrophils and other WBCs to the injury site
Animation
Phagocyte Chemotaxis and the Inflammatory Response
• Animation Link
• Leukocyte Migration Animation
Other Nonspecific Defense Systems • Antimicrobial proteins attack pathogens directly or indirectly
– Interferon and complement proteins
• Complement Protein Animation
• Interferons (IFNs) are small proteins that are secreted by cells infected by viruses to protect other cells which have not been infected.
– Stimulate synthesis of PKR protein that interfers with vial replication in healthy cells
– Lymphocytes secrete gamma interferon; leukocytes secrete alpha interferon
– Also can activate NK cells and macrophages which have anti-cancer capabilities (attack malignant cells)
InterferonAnimation
Complement Proteins • Includes 20 plasma proteins which circulate in their inactive form in the blood. They are nonspecific!
• When activated they release chemical mediators which:
– Amplify the inflammatory process
– Kill pathogens via lysis
– Complements both innate and adaptive (specific responses)
– Activated via the classical pathway or alternative pathway
Complement Protein Animation
FeverThis is a systemic response to invading microorganisms
Pyrogens (chemicals) •released by leukocytes and macrophages exposed to a pathogen•cause the body’s temperature to be reset (hypothalamus)
Mild or moderate fevers cause the liver and spleen to hold onto iron and zinc (necessary for bacteria to replicate)
Increases the metabolic rate of cells which increases healing.
▫High temperature ‘denature’ enzymes