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Microbiology > Chapter 14 The Innate Immune Response > Flashcards

Chapter 14 The Innate Immune Response Flashcards

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1
Q

Overview of Innate Immunity

A
  • Refers to defences that are present at birth
  • Non-specific - act against all (most) microbes in the same way
  • No memory component - cannot recall previous contact with an invader
  • Always present - it is active before an infection occurs - Responds Rapidly
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2
Q

First Line Defences

A

Physical and chemical barriers that prevent microbes from entering the body
Examples: Skin, Mucous Membranes, and Fluid Flow

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3
Q

Skin (Physical Barriers)

A
  • Outer surface of skin consists of dead cells and keratin
  • Frequently shed - removes microbes
    -Dry - inhibits growth of microbes
    Skin infections are more common on moist areas of skin, or in moist environments
    -Outer layer of skin is an excellent defence - rarely penetrated by microbes
    Most infections occur under the skin after skin has been broken
    -Some microbes are able to eat dead skin cells and oils secreted by the skin - Results in body odor
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4
Q

Mucous Membranes (Physical Barriers)

A
  • Involved in fluid or gas exchange
  • Offer less protection than the skin
  • Line our “tracts” - ex. Diestive tract
  • Secrete mucous - a glycoprotein - keeps membrane from dying (cracking) - Traps microbes
  • Mucocilliary Escalator - Cilia sweep mucous away
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5
Q

Fluid Flow (Physical Barriers)

A

Saliva, tears, urine, vaginal secretions - move microbes away from the body

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6
Q

Antimicrobial Substances (Chemical Barriers)

A

1) Acidity of Body Fluids and Skin
2) Lysozyme
3) Lactoferrin
4) Defensins
5) The Normal Microbiota

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7
Q

Acidity of Body Fluids and Skin (Chemical Barriers)

A
  • Stomach acid - pH 2
    Destroys many bacteria and toxins
  • Skin - fatty acids and lactic acid - pH 3-5
    Prevents growth of many microbes
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8
Q

Lysozyme (Chemical Barriers)

A
  • Enzyme that degrades peptidoglycan

- Found in sweat, tears, saliva, nasal secretions

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9
Q

Lactoferrin (Chemical Barriers)

A
  • Iron binding proteins in milk, mucous - Makes iron unavailable to slow growth of microbes
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10
Q

Defensins (Chemical Barriers)

A
  • Short polypeptides
  • Poke holes in microbial membranes
  • Produced by epithelial cells
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11
Q

The Normal Microbiota (Chemical Barriers)

A
  • Acquired shortly after birth

- Prevent growth of pathogens - competitive exclusion and microbial antagonism

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12
Q

The Second Line of Defence

A

Cells of the Immune System
- Leukocytes - White Blood Cells
Always found in normal blood, but increase in response to infection
- Phagocytes - White blood cells that use phagocytosis to “eat” microbes

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13
Q

Granulocytes

A

Have large granules in their cytoplasm - visible with light microscope

1) Basophils
2) Eosinophils
3) Neutrophils

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14
Q

Basophils - weak phagocytes

A
  • Secrete chemoattractants

- Release histamine - causes inflammation, allergies

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15
Q

Eosinophils

A
  • Destroy large pathogens
  • Ex. Parasitic Worms
  • Produce extracellular digestive enzymes to attack the parasite
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16
Q

Neutrophils - Strong phagocytes

A
  • Polymorphonuclear

- Can leave the blood and migrate into tissues to destroy invading microbes

17
Q

Mononuclear Phagocytes

A

Also have granules - but they are not visible under light microscope

1) Monocytes
2) Dendritic Cells

18
Q

Monocytes - initially non-phagocytic

A
  • Leave blood, enter tissues and change into macrophages - strong phagocytes
  • Often found in organs - filter out invading pathogens as blood passes through
19
Q

Dendritic Cells

A
  • Phagocytize foreign material and bring it to the adaptive immune system for ‘inspection’ - antigen presentation
20
Q

Lymphocytes

A

Natural Killer Cells (NK cells)

  • Responsible for killing infected body cells and tutor cells
  • Attack any body cell that displays unusual proteins in the cytoplasmic membrane
  • T and B lymphocytes - part of adaptive immunity
21
Q

Molecular Defences

A

The Complement System

  • About 30 proteins that circulate in blood
  • Work together in a cascade - action of one protein triggers action of the next
  • Complement can be triggered several ways: Small molecules binding to the surface of invading microbes
22
Q

Results of Activating the Complement Cascade

A

1) Opsonization
2) Enhance Inflammation
3) Lysis of Foreign Cells

23
Q

Opsonization

A

Attach to microbes and act as a flag to attract phagocytes - increases phagocytosis by 1000x

24
Q

Enhance Inflammation

A
  • Increase blood vessel permeability

- Attract phagocytes to infection site

25
Q

Lysis of Foreign Cells

A
  • Formation of membrane attack complexes (MACs)
    Pokes holes in membranes
    Kills Gram negative bacteria, but not Gram positive bacteria
26
Q

The Inflammatory Response

A
  • In response to tissue damage: blood vessels dilate, fluids leak and leukocytes migrate into tissues
    1) More blood reaches area
    2) Allows phagocytes to enter tissues - increased phagocytosis
    3) Brings platelets to form blood clots, and nutrients for faster repair
27
Q

Signs and Symptoms of Inflammation

A
  • Pain, swelling
  • Heat, redness
  • Edema
  • Loss of Function
28
Q

Fever

A

Can be triggered by toxins, LPS or chemicals produced by the immune system

29
Q

Fevers result in

A
  • Rapid muscle contraction (shivering)

- Increase temperature

30
Q

Fevers Benefit

A
  • Faster phagocytosis
  • Slows growth of heat limited microbes
    Ex. E. coli prefers to grow at 37C, growth slows at 40C
  • Faster metabolism - healing
  • Up to a certain temperature, fever is a defence against disease
31
Q

Fever Drawbacks

A
  • Uncomfortable

- Fever above 43C can cause death

32
Q

Anti-viral Interferons (IFNs)

A
  • Produced when cells detect viral RNA
  • Released by infected cells to warn neighbouring cells
    Induces neighbouring cells to enter into an antiviral state
    Does not help cells that are already infected
    Neighbouring cells undergo apoptosis if infected

Microbiology (17 decks)

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