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Foundations Of Medicine > 10.2 The Innate Immune System > Flashcards

10.2 The Innate Immune System Flashcards

1
Q

What types of barriers exist within the static barrier of the innate immune system?

A
  • Mechanical
  • Chemical
  • Microbiological
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2
Q

Is the epidermis permeable to bacteria?

A

No

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3
Q

How does sebum play a role in killing bacteria?

A
  • Changes pH down to about 3-5 due to lactic and fatty acid release
  • Denatures enzymes in bacteria -> death
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4
Q

Where can mucous membranes be found?

A
  • Respiratory tract
  • Gastrointestinal tract
  • Urogenital tract
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5
Q

What does mucous contain?

A
  • Mucin (glycoprotein)
  • Anti-microbial proteins
  • Inorganic salts
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6
Q

When commensal microbes digest dietary fibres, what do they produce?

A
  • Metabolites
  • Vitamins
  • SCFAs
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7
Q

How do commensal microbes fight with pathogenic microbes?

A
  • Lactic acid produced by lactobacilli (too acidic for some pathogens)
  • Bacteriocin production (antimicrobial peptides)
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8
Q

How can commensal microbes cause disease?

A
  • Called “opportunistic pathogens”
  • Take over in situations where the immune system is distracted by weakness/stress of some kind
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9
Q

General mode of action of AMPs (+Charge)

A
  • Cationic proteins
  • Disrupt membrane integrity/cell anabolism
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10
Q

Where are AMPs produced?

A
  • Keratinocytes
  • Mucosa
  • Neutrophils
  • Macrophages
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11
Q

Why do AMPs preferentially disrupt bacterial membranes over mammalian membranes?

A
  • Bacterial membranes have negative charge, whereas mammalian cells do not
  • AMPs are positive (therefore attracted)
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12
Q

What are the three pathways by which the complement system can be activated?

A
  • Classical pathway
  • Alternative pathway
  • Lectin pathway
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13
Q

Describe the classical pathway of complement activation

A

C’ recognising antibody:antigen complex

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14
Q

Describe the alternative pathway of complement activation

A

C’ binding generally to microbe surface

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15
Q

Describe the lectin pathway of complement activation

A

C’ binding to sugar residues on bacteria surface

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16
Q

What are the three outcomes following complement activation?

A
  • Opsonisation
  • Initiation of inflammatory response
  • Punching holes in cell membranes
17
Q

What complex punches holes in cell membranes following complement activation?

A

Membrane Attack Complex (MAC)

18
Q

What is released to trigger the inflammatory response following complement activation? What does this also do?

A
  • Anaphylotoxins are released
  • Chemoattractants to phagocytes
19
Q

Describe opsonisation following complement activation. Which proteins are used?

A

Coats microbe surface with C3b proteins to promote phagocytosis

20
Q

When can a monocyte differentiate to become a macrophage?

A

When migrating from blood to tissue

21
Q

Which immune cell is the number one defence against prokaryotes?

A

Neutrophils

22
Q

What cells do NKCs target?

A
  • Tumour cells
  • Cells affected by virus
  • Cells affected by intracellular bacteria
23
Q

Which cells take care of intracellular/extracellular bacteria?

A

Intracellular: NKCs
Extracullular: Neutrophils and macrophages

24
Q

Phagocytosis vs endocytosis

A

Phagocytosis: Whole organisms and other cells
Endocytosis: Macromolecules

25
Q

What are the two mechanisms of endocytosis other than phagocytosis?

A
  • Pinocytosis (invagination to form vesicles, vesicles form endosome, digested by lysosomes)
  • Receptor-mediated endocytosis (bind to receptor, form vesicles, vesicles form endosome, endosome digested by lysosome)
26
Q

Endocytosis vs phagocytosis: what do the vesicles form when combined?

A

Endocytosis: endosome
Phagocytosis: phagosome

27
Q

What soluble proteins are used to tag microbes to make them more “palatable” for phagocytes?

A

Opsonins

28
Q

How do opsonins make microbes more palatable?

A
  • Bind to substance
  • Phagocytes have receptor for opsonin -> phagocytoses
29
Q

What receptors facilitate direct microbe recognition that triggers phagocytosis?

A
  • Pattern recognition receptors (PRRs)
30
Q

Which patterns do PRRs detect in gram negative/positive bacteria?

A

Gram-positive: Lipoteichoic Acid
Gram-negative: Lipopolysaccharide

31
Q

What kinds of receptors are used during indirect microbe recognition that triggers phagocytosis?

A

Opsonin receptors

32
Q

What are the two kinds of opsonin receptors, and what do they bind to?

A

FcR: Butt end of antibodies
C3bR (Complement protein C3b)

33
Q

How do NKCs recognise tumour/infected cells?

A

They recognise that something is not right

Foundations Of Medicine (98 decks)

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