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PHAR20400 > HOST DEFENCE 1 > Flashcards

HOST DEFENCE 1 Flashcards

1
Q

Give examples of viruses? (2)

A
  • Influenza
  • Polio mellitus
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2
Q

Give some examples of parasites? (3)

A
  • Tapeworms
  • Malaria
  • Helminths
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3
Q

What are the benefits of the immune system? (2)

A
  • Protection from invaders
  • Eliminates altered self cells
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4
Q

What are the negative effects of the immune system? (2)

A
  • Discomfort (inflammation)
  • Damage to self (autoimmunity)
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5
Q

What are the two major elements of the immune system?

A
  1. Innate immune system
  2. Adaptive immune system
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6
Q

List 4 innate defence mechanisms

A
  • Anatomic resisting barriers e.g skin, mucous
  • Physiological barriers e.g temp, pH
  • Phagocytosis
  • Inflammatory defensive barriers e.g vasodilation, increase in capillary permeability, influx of phagocytes
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7
Q

What is the role of epithelia in innate immunity? (3)

A
  • Physical barrier
  • Antibiotics - locally produced on epithelial tissue
  • Intra-epithelial lymphocytes - live on the skin
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8
Q

What are the four soluble factors that the innate immune system uses to provide defence against bacterial infections?

A
  • Lysozymes
  • Acute phase proteins
  • Complement
  • Interferons (cytokines)
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9
Q

What is the role of lysozymes?

A

Splits the peptidoglycan wall of susceptible bacteria, this ruptures the extracellular membrane

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10
Q

What is the role of acute phase proteins e.g. C reactive protein?

A
  • Opsonization
  • Attraction of phagocytes
  • Increased blood flow - in areas where there’s a high conc. of foreign pathogens (this brings several chemicals and cells which are required to eliminate potential pathogens) = part of inflammation
  • Basically activate complement
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11
Q

What are complements?

A

A group of 20 serum proteins with the role of opsonization

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12
Q

What are interferons?

A

Provide antiviral resistance (break down viral wall)

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13
Q

What is opsonization?

A

Formation of a coating surface around the pathogen, so the pathogen can be identified more easily

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14
Q

What cells are part of the innate immune system? (two)

A
  • Phagocytes: engulfs particles
  • Natural killer NK cells: recognises cell surface changes occurring on virally infected and tumour cells
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15
Q

Where do all cells of the immune system arise from?

A

Pluripotent hemopoietic stem cells

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16
Q

What can pluripotent hemopoietic stem cells differientate into?

A
  1. Myeloid stem cells
  2. Lympoid stem cells
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17
Q

What can Myeloid cells differentiate into? (2)

A
  • Granulocytic stem cells
  • Monocytic stem cells
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18
Q

What can granulocytic stem cells differentiate into? (3)

A
  • Neutrophils
  • Basophils
  • Eosinophils
19
Q

What can monocytic stem cells differentiate into? (4)

A
  • Macrophages
  • Langerhans & Kupffer cells
  • Dendritic cells
20
Q

What can lymphoid cells differentiate into?

A
  • T cells (THELPER TCYTOTOXIC)
  • B cells (plasma cells)
21
Q

How do specialised cells develop from stem cells?

A
  • Cytokine growth factors
  • The development of a progenitor cell (committed cell, meaning that it is committed to that line of cell growth)
    • e.g. an eosinophil progenitor must become an eosinophil
22
Q

Describe the structure of monocytes?

A
  • Larger than lymphocytes
  • Have ONE horseshoe-shaped nucelus
  • Often contain faint azurophillic granules
23
Q

What’s the function of monocytes?

A

Precusor of Macrophages, Langerhans, Kupffer, and Dendritic cells

24
Q

How do macrophages recognise microbes and give an example of a receptor?

A

Through different Pattern Recognition Receptors (PRR) such as Toll-like receptor.

25
Q

How do macrophages present the antigens of a pathogen on it’s surface?

A
  • The macrophage produces an MHC Class II molecules
  • This binds the degraded peptides of the pathogen and transfers the peptides to the outer surface
  • So the peptides can be detected by Th1 cells
26
Q

What are the functions of macrophages? (4)

A
  • Phagocytosis
  • Intracellular and extra-cellular killing
  • Tissue repair
  • Antigen presentation
27
Q

What is the structure of neutrophils? (2)

A

Are polymorphonuclear

  • This means they have a nucleus with several lobes and a cytoplasm that contains granules (these granules are not acidic or basic)
28
Q

What is the difference between macrophages and neutrophils? (5)

A
  • Neutrophils aren’t antigen-presenting cells
  • Neutrophils are found in the blood and macrophages are found in the tissue
  • Neutrophils nucleus has several lobes and macrophage has a horse-shoed nucleus
  • Neutrophilis has lots of granules
  • Neutrophilis are at the infected site first
29
Q

What are the four types of PRRs?

A
  • Fc receptors – activate phagocytosis
  • Complement receptors – bind to C3b-coated bateria and results in enhanced phagocytosis
  • Scavenger receptors – Bind to polyanions on bacterial surfaces = recognition + phagocytosis
  • Toll-like receptors – recognize PAMPs + phagocytosis
30
Q

What are the three stages involved in killing of opsonised microbes?

A
  1. . In the innate immune response this occurs via Complement Receptors and in the adaptive immune response by Fc receptors. In both systems, pattern recognition receptors (PRR) are also needed to identify the organism.
  2. The microbe is ingested by the pseudopodia of the phagocyte (forms a phagosome)
  3. Metabolic reactions take place in phagosome, generating oxygen and nitrogen radicals which damage microbes
  4. formation of phagolysosomes = reduction reactions + low pH and lysosomal enzymes = death of microbe
31
Q

In the killing of opsonised microbes, pseudopodia ingest the microbe. How does this differ in innate and adaptive response?

A
  • In innate - complement receptors carry this out
  • In adaptive - Fc receptors carry this out
  • Both systems require PRRs
32
Q

What do basophil contain? (2)

A
  • Contain glycogen
  • Contain deep violet-blue granules (contain histamine and are acidic)
33
Q

Which complements do basophils bind?

A

C3a, C3b and C5a

34
Q

How do eosinophils work?They gather at a parasitic infection or site of allergic reaction such as asthma
they release their toxins, contained in their granules

A
  • Eosinophils gather where there is a parasite infection or an allergic reaction such as allergic asthma
  • They degranulate releasing the contents of their granules (peroxidase and histaminase)
35
Q

How do NK cells know which host cells are infected?

A
  • Virally infected cells inhibit the expression of MHC Class I molecules = reduced expression of MHC class I
  • Virally infected cells don’t respond to IFNα and IFNβ (MHC Class I aren’t produced)
36
Q

When both receptors on NK cells are occupied, the NK cell becomes activated. True or false?

A

False - not activated when both receptors are occupied so doesn’t kill virally infected cells

37
Q

When the activating receptor is occupied (not the inhibitory one) what happens?

A

The NK cells receive a signal to secrete chemicals that kill virally infected cells

38
Q

What’s the complement pathway/ overview of innate immune response? (4)

A
  1. Mast cells are activated causing vasodilation and increased capillary permeability to bring immune cells to the site of infection
  2. Permeable capillaries allow influx of fluid and cells
  3. Phagocytes + neutrophils move to site of inflammation (chemotaxis)
  4. Phagocytes and antibacterial destroy bacteria
39
Q

What are cytokines (interferons)?

A

Toxic to viruses

40
Q

What shows resistance to phagocytosis and how does it do this?

A

Pneumococcus

  • Capsular polysaccharide inhibits phagocytosis
41
Q

What shows resistance to reactive oxygen intermediates in phagocytes and how does it do this?

A
  • Staphylococci
  • Produces catalase which breaks down oxygen intermediates
42
Q

What shows resistance to complement activation (alternative pathway) and how does it do this?

A
  • Neisseria meningitides: expresses sialic acid which inhibits C3 and C5 convertases
  • Streptococcus: M protein blocks C3 binding to organism and C3b binding to complement receptors
43
Q

What shows resistance to antimicrobial peptide antibiotics and how does it do this?

A
  • Pseudomonas
  • Synthesis of modified LPS that resists action of peptide AB’s

PHAR20400 (20 decks)

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