3 - Innate Immune System Flashcards Preview

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Flashcards in 3 - Innate Immune System Deck (30)
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1
Q

What is the definition of the immune system and an infectious disease?

A

- Immune system = cells and organs that contribute to immune defences against infectious and non-infectious diseases e.g cancer

- Infectious Disease: When a pathogen succeeds in evading or overwhelming the host’s immune defences

2
Q

What are the main roles of the immune system?

A
  • Recognise pathogen
  • Contain infection and eliminate
  • Regulate itself to prevent damage to host
  • Remember pathogen
3
Q

What are the differences between the innate and adaptive immunity?

A
4
Q

What are the different categories of innate barriers and what is their role?

A
  • Chemical
  • Physiological
  • Biological
  • Physical

PREVENT ENTRY AND LIMIT GROWTH OF PATHOGENS

5
Q

What are some physical innate barriers?

A
  • Skin
  • Mucous membranes with lymphatic tissue
  • Bronchial cilia
6
Q

What are some physiological innate barriers?

A
  • Vomiting
  • Diarrhoea
  • Coughing
  • Sneezing

Expulsion from body

7
Q

What are some chemical barriers?

A
  • Low pH (skin, vagina, stomach)
  • Antimicrobial molecules
8
Q

What are some antimicrobial molecules in the innate immune response?

A
  • IgA (tears): prevent microbe attaching
  • Lysozyme (sebum and urine): punch holes in bacteria
  • Mucus
  • Beta-defensins
  • Gastric acid
9
Q

What are some biological innate barriers?

A

Normal non-pathogenic flora in strategic locations such as nasopharynx, mouth, skin, GI

Not present in internal organs or tissues

10
Q

What are the benefits of having normal flora in the body?

A
  • Immune maturation
  • Produce antimicrobial substances
  • Synthesise vitamins (K and P)
  • Compete with other pathogens
11
Q

What are some normal flora that inhabit the skin and nasopharynx and what can they cause if displaced?

A
12
Q

Why are antibiotics given before dental treatment?

A

Poor dental hygeine could lead to bacteria getting into the blood stream when dental work takes place and can lead to sepsis

13
Q

What patients are high risk for developing serious infections?

A
  • Hyposplenic/Asplenic patients
  • Patients with damaged or prosthetic heart valves
  • Patients with previous infective endocarditis
14
Q

What is the issue with infections when a patient is immuno-compromised?

A

Patient has a weaker immune system so can’t prevent overgrowth of normal flora, e.g in diabetes, aids, chemotherapy

15
Q

What type of cell is needed for adaptive immunity?

A
  • Dendritic cells
16
Q

What are the key properties of macrophages?

A
  • Present in all organs
  • Present antigens to T-cells
  • Produce cytokines/chemokines
17
Q

How are macrophages and neutrophils linked?

A

The neutrophils reccruited by chemokines to the site of bacteria and they desroy pyogenic bacteria, e.g Staph aureus and strep.pyogenes

18
Q

How do phagocytes recognise their pathogen?

A

- PAMPS on pathogens: structures not on host cell, e.g lipids, proteins, nucleic acids

- PRR on phagocytes e.g TLR4

19
Q

What is opsonisation?

A

Coating proteins called opsonins that bind to microbial surfaces leading to enhance attachment of phagocytes and clearance of microbes

Used in conjuction with PAMPS

20
Q

What are some examples of opsonins?

A

Complement proteins: C3b, C4b

Antibodies: IgG, IgM

Acute phase proteins: CRP, Mannose-binding lectin

21
Q

What is the process of phagocytosis?

A
22
Q

What is the difference between the first and second line of defence in innate immunity?

A
23
Q

How is the complement system activated and what are some of the main complement proteins involved in innate immunity?

A

1. Alternative pathway - initiated by cell surface microbial constituents e.g endotoxins like LPS

2. MBL pathway - when MBL binds to mannose containing residues of proteins on microbes e.g salmonella, neisseria

24
Q

What do chemokines/cytokines stimulate?

A
  • Phagocytic activation
  • Chemotaxis
  • Inflammation

(ones in red are macrophage dervied cytokines and the picture is the effects theses have)

25
Q

Summarise the five steps of the innate immune response.

A
26
Q

What are some risk factors for neutropenic sepsis?

A
  • Asplenic/hyposplenic
  • Chemotherapy
  • Drugs lowering neutrophils, e.g phenytoin
  • Chronic granulomatous disease (no respiratory burst)
  • Chediak-Higashi syndrome (no phagolysosome)
27
Q

In general, why are people with chronic granulomatous disease susceptible to large infections?

A

They lack the enzyme NADPH oxidase, so cannot produce superoxide to destroy bacteria

28
Q

What is the acute phase response?

A

Where acute phase proteins are released from the liver in response to cytokines leading to things such as vasodilatation and increased body temperature

29
Q

What is the function of CRP?

A

Released by the liver in response to inflammatory cytokines, about 4-6h after injury/inflammation. Rapidly decreases

  • Opsonisation of damaged self and pathogens
  • Interact with Fc receptors to release inflammatory cytokines
  • Activates complement and adaptive immunity
30
Q

What is the single most important function of CRP?

A
  • Opsonin-mediated phagocytosis
  • Binds to phosphocholine on dead or dying cells anf bacteria, promoting phagocytosis