Innate and Acquired Immunity

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Innate and Acquired Immunity
Lecture 3
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Agenda

• Distinction between innate and specific immunity
• Discuss mechanisms of innate immunity
• Barriers
• Recognition of invading microorganisms
• Phagocytosis
• Inflammation

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Innate Immunity
Specific Immunity
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Innate Immunity

• Refers to various PHYSICAL, CHEMICAL, and
  CELLULAR attributes that collectively represent
  the first line of defense against infectious
  disease.

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Innate Immunity

• Natural Immunity
• Phylogenetically older Present in all
  Multicellular Organisms
• Use Proteins Encoded in the Germline (Elements an
  Individual is born with Standard
  Equipment-Hard-Wired

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Innate Immunity Features

• Preformed Rapid-Available on Short Notice
• No MemoryNot Enhanced by Prior Exposure
• Broad Specificity
• Dependent on species, strain, sex.

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Acquired/Specific Immunity

• Acquired Following Exposure to the Microorganism.

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Acquired/Adaptive/Specific Immunity Features

• Specificity
• Memory
• Specialization
• Self/Nonself recognition

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Innate vs. Acquired Immunity

• Innate/Natural/ Nonspecific
• present from birth
• operates against any substance
• not enhanced by prior exposure

• Acquired/Adaptive/Specific
• defense mechanisms tailored to individual
  pathogens
• enhanced by prior exposure

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Mechanisms/Components of Innate Immunity

• Anatomic barriers
• Physiologic barriers
• Phagocytic/Cellular Barriers
• Inflammatory Barriers

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Anatomic Barriers

• External/First line of defenses
• Epithelial Barrier
• Skin
• Mucous membranes
• Conjunctivae, GI, resp, urogenital tracts
• secretions (saliva, tears, urine, mucus)
• wash/trap/inhibit growth
• cilia

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Functions of Epithelial Barrier
Defensins
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Physiological Barriers

• Temperature-Fever
• pH-Stomach, vagina, and skin
• Normal microflora of GI tract, skin Superinfectio
  n
• Chemical Mediators
• Defensins-Secreted by Epithelia
• Hydrolytic enzymes of Saliva
• Lysozyme in tears

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Physiological Barriers (Contd.)

• Interferons-viral infection

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dsRNA
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Cellular Barriers

• Following Penetration of Anatomical and
  Physiological Barriers
• Specialized Cells Function is to Destroy Invader

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Recognition of Microbial Nonself

• Depends on recognition of Pathogen Associated
  Molecular Patterns (PAMPS)
• Gene products unique to microbes-Molecular
  Signatures of microbial invaders
• Conserved among microbes of a given
  class-Invariant
• Essential for microbial survival
• LPS (Gram negative bacteria) Peptidoglycan (Gram
  positive bacteria)

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Pattern Recognition Receptors (PRRs)

• Recognize PAMPs
• Receptors expressed on macrophages
• Signal to induce inflammatory cytokines and
  activate host defense mechanisms
• Examples
• Macrophage mannose receptor
• Macrophage Scavenging Receptor-LPS and Gram neg.
  bacteria
• Toll-like Receptors

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Receptors of The Innate Immune System
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TOLL-LIKE RECEPTORS
Unmethylated CpG DNA
LPS (G-ve)
Peptidoglycan (Gve) Zymosan (Yeast) Bacterial
lipopeptides
Flagellin
dsRNA
Bacterial Lipoproteins Parasite surface proteins
Viral ss RNA
TLR3
TLR8
TLR4
TLR2
TLR6
TLR9
TLR7
TLR1
TLR5
TLR2
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Receptors and Responses of Phagocytes in Innate
Immunity
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Phagocytosis

• Eating by Cells
• Ingestion/Engulfment and Destruction of Invading
  Foreign Particles such as Bacteria
• 1883 Metchnikoff

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Professional Phagocytes

• Neutrophils
• Macrophages

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Phagocytosis of Bacteria by Macrophages
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Phagocytosis

• Adherence and Opsonization
• Ingestion
• Destruction

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Opsonins and Opsonization
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Adherence and Opsonization

• Adherence to Surface Receptors
• Mannose Receptor
• Scavenger Receptor
• Opsonins Greek- Prepare food for
• Enhance Phagocytosis
• Antibodies-Fc Receptors
• Complement Proteins-Complement Receptors

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Resistant Pathogens

• Brucella abortus
• Listeria monocytogenes-Escape into the cytoplasm
• Mycobacterium avium, tuberculosis-cell wall lipid
  prevents phagolysosome formation
• Salmonella typhimurium
• Candida albicans

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Evasion of Innate Immunity by Microbes
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Inflammation

• Infection
• Injury
• Irritants