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Anatomy 2FF3 > Innate Immunity > Flashcards

Innate Immunity Flashcards

1
Q

What is immunology?

A

The study of the multi-layered “host defence” system that protects us against pathogens

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2
Q

Innate vs adaptive: speed

A

Innate system is much faster than the adaptive

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3
Q

Three layers of immunity

A

Intrinsic barriers, innate and adaptive

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4
Q

Intrinsic barriers

A

Pre-formed barriers to PREVENT invasion

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5
Q

Innate immunity

A
  • Non-specific
  • Fast
  • Fixed/constant (no ability to learn from prior exposure)
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6
Q

Adaptive immunity

A
  • Very specific
  • Slow
  • Improves throughout response (ability to learn)
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7
Q

Intrinsic barriers (x4)

A
  • Mechanical
  • Chemical
  • Physiological
  • Microbiological
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8
Q

Mechanical barriers

A
  • Expulsive force (coughing/sneezing/defecation etc.)
  • Ciliary beating (respiratory tract)
  • Tight junctions in the epithelium (prevents pathogens from entering)
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9
Q

Chemical barriers

A
  • Low pH barriers (stomach, vagina, sebaceous fatty acids - denatures pathogens)
  • Proteolytic enzymes (breaks down proteins; lysozyme and pepsin found in tears + gut)
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10
Q

Physiological barriers

A
  • Temperature regulation (fever)
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11
Q

Microbiological barriers

A
  • Commensal flora compete with pathogens; found in the GI tract, pathogens can only take control if they outcompete the flora, competes for nutrients and adhesion spots
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12
Q

What are zymogens?

A
  • Zymogen is the complement protein precursor - free floating in blood + tissues, made in the liver
  • Activated in 3 different ways; antibody-antigen binding, lectin-mannose binding and by pathogens
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13
Q

3 pathways for zymogen activation

A
  1. Classical pathway (antibody-antigen binding): zymogens get cleaved into their active form
  2. Lectin-mannose binding: lectin from the human body binds to mannose sugar found on the pathogen surfaces
  3. Alternative pathway: some pathogens themselves naturally have enzymes on their surface that cleave + activate zymogens
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14
Q

What happens when zymogen is activated?

A
  1. Inflammation: small fragments of complement proteins act on BVs to cause inflammation –> BV dilation and permeabilization occurs; proteins + cells are released into the tissue to defend the body
  2. Membrane attack complex formation: large fractions of complement proteins polymerize to form barrel-shaped structures aka membrane attack complexes
    • Pores are formed in the bacterial cell wall by the membrane attack complex
    • Bacteria are under a lot of pressure (human defence mechanisms get in & bacterial material out)
  3. Opsonization aka tagging: phagocytes will envelope opsonized pathogens (CPs are on the pathogen surface) –> they get digested in a way so they are no longer hazardous
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15
Q

Resident phagocytes

A

Phagocytic cells

  1. Macrophages: found in healthy tissues, takes big bites of pathogens to engulf
    • Bacteria binds to macrophage receptors & macrophage engulfs + digests the bound bacteria
  2. Dendritic cells: found in healthy tissues, does macropinocytosis; takes samples of pathogens and so the lymph nodes knows to turn on the adaptive immune system
  3. Neutrophils: recruited later and also does macropinocytosis
  • Phagosome fuses with lysosome to create a phagolysosome; digests pathogens
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16
Q

Inflammation activation

A
  • Pattern recognition receptors (PRRs): found on human cells to recognize pathogens
  • Toll-like receptors: example of PRRs that recognize pattern-associated molecular patterns (PAMPs) on pathogens –> initiates inflammation
    • Releases cytokines: allows for communication
    • Releases chemokines: brings in other cells to help signalling
16
Q

Inflammation activation

A
  • Pattern recognition receptors (PRRs): found on human cells to recognize pathogens
  • Toll-like receptors: example of PRRs that recognize pattern-associated molecular patterns (PAMPs) on pathogens –> initiates inflammation
    • Releases cytokines: allows for communication
    • Releases chemokines: brings in other cells to help signalling
    • Vasodilation + increased permeability allows for fluid/protein/inflammatory cells to blood –> tissue
    • After inflammation, buffy coat is larger (more WBCs)
    • Signs of inflammation: redness + swelling + heat + pain
17
Q

Innate immune cells

A
  1. Macrophages
  2. Neutrophils
  3. Dendritic cells
  4. Natural killer cells
  5. Mast cells
  6. Eosinophils
  7. Basophils
18
Q

Macrophages

A
  • Tissue resident “sentinel cells” –> senses + monitors presence of pathogens
  • Differentiate from monocytes which travel in the blood –> tissues and then stay there
  • Phagocytose bacteria + dead cells
  • Produce cytokines; causes inflammatory response
  • More are recruited to sites of infection when needed
19
Q

Neutrophils

A
  • Found in the body in high quantities
  • Migrate to tissues during inflammation
  • Recruited by chemokines; including IL-8
  • Contain toxic granules that can kill invaders
    • This must be regulated to prevent immunopathology
  • Short-lived, replenished by bone marrow
20
Q

Dendritic cells

A
  • Antigen-presenting cells found mostly in tissue
  • Differentiate from blood-borne monocytes –> tissue
  • Bridge the gap between innate & adaptive immunity by ACTIVATING T & B cells in the lymph nodes and spleen
  • Come from the same lineage as adaptive immune cells, but are a part of the innate response
21
Q

Mast cells

A
  • Important in allergic reactions: release histamine

- Help battle parasite infections (macrophages are too small for this)

22
Q

Eosinophils

A
  • Parasite infection + protection of mucosal surfaces (GI tract, lungs + genital tract)
23
Q

Basophils

A
  • Also important in allergic reactions: release histamine

- Release heparin to reduce blood clotting

24
Q

Innate response for extracellular bacteria

A
  • Phagocytosed by macrophages
    • Release cytokines + chemokines to attach more monocytes & neutrophils
  • Positive feedback loop
25
Q

Innate response for intracellular viruses

A
  • Infected cells (often epithelium) produce anti-viral cytokines (interferons)
    • Change in temperature (fever)
    • Recruitment of NK cells
    • Infected cells are killed
  • Phagocytes clean up released virus & dead cell material
26
Q

Lymphatic system

A
  • Drain the tissues of the body
  • Return fluid, proteins & cells to the blood via the thoracic duct
  • Bring together the components of the immune system
    • Lymphoid tissues
    • Lymph nodes
27
Q

Lymphoid tissues

A

Primary lymphoid tissues: where cells develop and are educated

  • Bone marrow: all immune cells are born here, B cells are also educated here
  • Thymus: T cells are educated here

Secondary lymphoid tissues: where immune components are brought together to mount a response

  • Lymph nodes (found in places where you’re likely to run into pathogens)
    • GALT/MALT: gut/mucus
    • BALT: bronchus; protects respiratory tract

Anatomy 2FF3 (26 decks)

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