3.9 Flashcards

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1
Q

Cell death
Lysis of host cells
1. growth of pathogen within host cells

A
• Cell membrane
damage causes cell
death (free radicalinduced lipid
peroxidation).
• Damage is
proportional to number
of bacteria inside cell.
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2
Q
  1. Cell death (continued)
    Lysis of host cells
  2. cell-mediated immunity
A
activated CD8+ cell encounters infected cell displaying pMHC class 1
reactivated CD8+ cell proliferated and makes contact with other cells that display the same pMHC class 1
CTL use perforin and granzymes to kill cells displaying appropriate pMHC class 1
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3
Q
  1. Cell death (continued)
    Lysis of host cells
  2. Membrane-damaging toxins
A

Apoptosis (programmed cell death)

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4
Q

Damage caused by host responses
Uncontrolled inflammation
due to

A

exaggerated adaptive immune response = hypersensitivities

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5
Q

Inflammation (3)

A

– healthy response
- increased blood supply (redness)
- increased vascular permeability (edema)
- chemotaxis (infiltration by phagocytes and
lymphocytes)

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6
Q

Type I hypersensitivity =

A

allergy but can lead to

anaphylaxis and shock

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7
Q

Type II hypersensitivity =

A

bound
antibodies leading to complement
and leukocyte activation to surfaces

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8
Q

Type III hypersensitivity =

A

bound antibodies
leading to complement and leukocyte
activation to soluble molecules, then immune
complex deposition (e.g in glomeruli)

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9
Q

Type IV hypersensitivity =

A

inflammation by purely CMI

responses (not antibodies)

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10
Q

Alteration of the metabolism of host cells

caused by —

A

toxins

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11
Q

Toxins

A

Microbial product or component that can injure another

cell or organism at low concentrations

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12
Q

Toxins act in different ways: (3)

A

Modulation of targets inside a host cell
Action in the extracellular matrix
Action on surface of a host cell

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13
Q

Toxin production and disease consequences vary widely

among

A

pathogenic bacteria

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14
Q

Like transposons, many toxin-encoding genes are carried

on

A

plasmids or temperate bacteriophage genomes (easy to

transfer to other, non-toxigenic bacteria).

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15
Q

ctxA and ctxB encode the

proteins that comprise

A

cholera toxin

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16
Q

Modulation of targets inside a host cell

Exotoxins -

A

secreted by pathogens

17
Q

Modulation of targets inside a host cell

Type III cytotoxins -

A

injected into host cells

contact-dependent

18
Q

Exotoxins are secreted

by

A

Type I or II secretion

systems

19
Q

Common features of exotoxins (3)

A
  1. A-B toxins (2 components)
  2. Require activation (proteolysis or reduction of disulfides)
  3. Many are ADP-ribosyltransferases
20
Q

Action of diphtheria toxin (an exotoxin)

Inhibits

A

translocation reaction

of protein synthesis

21
Q

Action on surface of a host cell

3

A

Membrane-damaging toxins
Superantigens
Endotoxin

22
Q

Membrane-damaging toxins

A

lipases, pore-forming toxins, hemolysins

23
Q

Endotoxin

=

A

LPS of gram negative bacteria

24
Q

Active toxin

part =

A

Lipid A

25
Q

Exoenzymes
collagenases, hyaluronidases, DNases
streptokinase (Streptococcus pyogenes)
activates

A

plasminogen (converts to plasmin)

help microbes spread

26
Q

Protection against exotoxins (2)

A

A. Immunization with toxoids
B. Treatment with antitoxins
passive immunization