immune system mic lec
TRANSCRIPT
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IMMUNE SYSTEM
MARLON M. MARAMION, MD, DPSP
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THE IMMUNE SYSTEM
• OBJECTIVES1.Know the components of the immune system2.Understand how each component functions in
the elimination of microorganisms
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IMMUNE SYSTEM
PHYSIOLOGIC FUNCTION protect the body against infectious pathogens
MECHANISM:INNATE IMMUNITYADAPTIVE IMMUNITY
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INNATE IMMUNITY
Natural ImmunityDefense mechanisms that are present even
before infection and have evolved to specifically recognize microbes and protect multicellular organism against infection
nonspecificFIRST LINE OF DEFENSE
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Mechanisms of Innate Immunity
• PhysiologicBarriers at the Portal of EntrY- skin- mucous membranes
• Alternative Pathway of Complement Activation
• Phagocytosis• Interferons• Natural Killer (NK) Cells
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SKIN• acid pH and certain chemical
substances (especially fatty acids)
• Lysozyme
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MUCUS MEMBRANES
• Mucus & cilia• Secretions (saliva, tears)• Lysozyme• IgA antibody• Phagocytes• pH• Normal flora
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Reticuloendothelial System
• mononuclear phagocytic cellsbloodlymphoid tissuesliverspleenbone marrowlungs and other tissues
- FILTER BLOOD AND TISSUE
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COMPLEMENT SYSTEM
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COMPLEMENT SYSTEM
• OPSONIZATION• MEMBRANE ATTACK COMPLEX FORMATION
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PHAGOCYTOSIS
• polymorphonuclear leukocytes (granulocytes)• phagocytic monocytes (macrophages)• fixed macrophages of the reticuloendothelial
system
OPSONIZATIONa. C3 component of the complement systemb. Fc portion of antibody
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NEUTROPHILS
•60-70% of WBC•12-15 µm•Nucleus – 2-5 lobes•Lifespan – 6-7 hrs
•Function- PHAGOCYTOSIS
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NEUTROPHILS• MICROBIAL KILLING1. Non oxidative process
- lytic enzymes- Lysozyme (destroys Peptidoglycan of
bacterial cell wall)- Lactoferrin (binds iron)
2. Oxidativea. generation of H2O2- acted upon MPO + cofactors (halides) + acid = HOClb. production of superoxide anion (O2
–)- directly lethal for many microorganisms
PUS
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Monocytic (Mononuclear) Phagocytic System
• Principal cells– Monocytes and Macrophages
• Monocytes circulate in the blood (1-3%) for a few days, then migrate in the tissues as macrophages
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Macrophages Types
• Tissue and fixed macrophages– Kupffer cells, histiocytes, splenic macrophage,
alveolar macrophages, mesangial cells, microglial cells, osteoclasts
• Giant and epitheloid cells– Granuloma formation
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MacrophagesReceptors
• Chemokines and cytokines• Complement components• Fc receptors• Class I and II antigens for Ag presentation
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MacrophagesActivation
• By gamma interferon which are released by activated T helper 1 subset
• More efficient in intracellular killing activities
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MacrophagesFunctions
• Phagocytosis• Antigen processing• Antigen presentation• Secretory cells
– IL-1, IL-6, TNF-a
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Phagocytosis
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Phagocytosis Mechanisms Of Microbial Killing
• Oxygen-dependent reactions– Myeloperoxidase-mediated
• MPO + H2O2 form aldehydes and hypochlorites which have powerful antimicrobial activity
– MPO-independent• H2O2, superoxide anions, hydroxyl radicals and singlet
O2
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Phagocytosis Mechanism Of Microbial Killing
• Oxygen-independent reactions– Intracellular accumulations of lactic acid– Lysozymes– Cationic proteins– Lactoferrin and transferrin– Ceruloplasmin– LYTIC ENZYME
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INTERFERONS
• Antiviral proteins• Interferon α (IFN- A) and interferon β (IFN-B)
& interferon γ (IFN-G)• produced by virally infected cells & activated
lymphocytes• control viral replication by inhibiting protein
synthesis & viral multiplication.
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Natural Killer Cells- 10-20% of the circulating lymphocytes- Larger than small lymphocytes- Abundant azurophilic granulesRECEPTORSa. "activating receptor" - recognizes
carbohydrate ligandsb. "inhibitory receptor" - recognizes MHC
class I molecules- Kill:
Tumor cellsVirally infected cells
First line of defense
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INNATE IMMUNE MECHANISM
• Phagocytosis• Inflammation
- IL-1 & TNF α release by macrophages- generation of prostaglandins- fever