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MEDI2000 - IMMUNOBIOLOGY 2021 > 2 - INNATE AND ADAPTIVE IMMUNITY > Flashcards

2 - INNATE AND ADAPTIVE IMMUNITY Flashcards

1
Q

Describe the general characteristics of innate immunity

A

Non specific
Do not require previous exposure
Present at birth
Immediate response, no memory cells
Recognises surface molecules that are common among many pathogens
Provides initial discrimination between self and non-self entities
Initially inhibits spread of invaders

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2
Q

Functions of the innate system

A

Initial defence against microbes - preventing spread, eliminates and controls

Eliminates damaged cells and initiates repair

Stimulates adaptive immune response

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3
Q

Innate defences: surface barriers

A

Physical barrier: skin and mucosal surfaces - to trap microbes and carried to external surfaces via ciliated epithelial cells

Cough reflex: prevents entry into the RT

GIT: acidic pH, proteolytic enzymes are not an ideal environment for microbial survival

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4
Q

Innate defences: internal defence

A

Specialist cells: destroy invading microbes

  • Macrophages and neutrophils: phagocytosis and activation of bactericidal mechanisms
  • Dendritic cells: antigen presentation in lymph nodes
  • NK cells

Inflammation

Antibacterial peptides
- amino acids with anti-microbial activity
- defensins: kills a wide range of bacteria, some fungi and enveloped viruses
Secreted by neutrophils, epithelial cells and paneath cell
Disrupts the microbe membrane causing lysis

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5
Q

Describe the process of inflammation

A

Injury causes the release of inflammatory mediators
Acute inflammation removes damaging stimulus which can either result in:
- cell regeneration: restore normal function and structure
- no cell regeneration: healing by repair and scar formation

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6
Q

What processes begin inflammation?

A

Tissue/cellular injury
Attempt to prevent spread of agent
Disposal of debris and pathogens
Tissue repair

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7
Q

What are the signs of inflammation?

A 
Redness
Heat 
Swelling 
Pain 
Loss of function
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8
Q

What are the types of inflammatory mediators

A

Cytokines: proteins that are released by cells that affect other cells

Chemokines: proteins released by cells to attract other cells to the area

Acute-phase proteins: plasma proteins that increase in concentration with inflammation

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9
Q

Provide examples of acute phase proteins and their mechanisms

A

C reactive protein: binds microbes and activates complement

Kinins: locally induce vasodilation

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10
Q

Describe the process of phagocytosis

A
  1. Phagocytic cell recognises surface of microbe, adheres and takes in microbe
  2. Held within phagosome and fuses with lysosome to form a phaglolysosome
  3. Toxic substances kill and degrade microbe -
    - nitric oxide
    - superoxide anions
    - hydrogen peroxide
  4. Exocytosis to remove debris
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11
Q

Describe the mechanism of NK cells

A

NK cells recognise reduces MHC I molecules via receptors

ADCC: Antibody dependent cell mediated cytotoxicity - NK cells attach to abys via Fc receptor on cell surface

Direct cytotoxicity by release of perforin and granzymes

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12
Q

How does the inhibitory receptors of NK cells work

A

When inhibitory receptor is engaged
- NK cell is not activated = no cell killing

When inhibitory receptor is engaged
- NK cell is activated = cell killing

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13
Q

How is the innate system stimulated

A

PAMPs - pathogen associated molecular patterns

DAMPs - damage associated molecular patterns

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14
Q

Describe the mechanism of PAMPs

A

When the cells of the immune system, recognises a particular structure on a pathogen a response is stimualated

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15
Q

Give examples of the structures on pathogens that are recognised by PAMPs

A

Virus: nucleic acid - ssRNA, dsRNA, cpG

Bacteria: proteins - pilin, flagelin

GNB: cell wall - lipids

When cells of the innate system recognise lipids found on the cell wall on a GNB a response is stimulated

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16
Q

Describe the mechanism of DAMPs

A

Damaged cells will release molecules in response to trauma resulting in healthy cells releasing alarmins to enhance the innate response

17
Q

Describe how pattern recognition receptors on cellular phagocytes work

A

Dendritic cells, macrophages and neutrophils have TLR that bind to PAMPs/DAMPs activates a signal transduction pathway to promote inflammation and anti-microbial activity

18
Q

Provide examples of TLR, their location and the PAMP/DAMP they bind to.

A

TLR 1 - bacterial lipoproteins found on cell membrane binds to microbial molecules via LPS or viral nucleic acid

19
Q

Provide examples of TLR found on cell membranes

A

TL-1: Bacterial lipoproteins
TL-2: Bacterial peptidoglycan
TL-4: LPS
TL-5: Bacterial flagelin

20
Q

What are NOD-like receptors

A

NOD: nucleotide binding oliomerisation like receptors
Are specific for intracellular pathogens
These receptors are found in the cytosol of cells
Are activated by peptidoglycan, RNA, toxins and flagellin
They release pro-inflammatory cytokines: IL1, IL6, TNFa and IL8

21
Q

What are the groups of interferons and what is their function

A

IFNa, IFNb and IFNy

IFNa and IFNb are produced in response to viral infection
INFy are inflammatory - macrophages, B cells and T helper cells

22
Q

Describe the mechanism of interferons

A

Binds specific receptors of neighbouring cells

  • neighbouring cell produces PKR: blocking virus entry
  • Limits spread of viral infections
  • Stops production of protein in cells -> inhibiting virus production
  • Stimulates endonuclease production -> Degrades viral mRNA
23
Q

What are APCs

A

Antigen presenting cells
Phagocytose antigens
APCs migrate to the lymph node and digests + presents antigens to T helper cells via MHC II

24
Q

What are the types of APCs

A

Dendritic Cells

Macrophages

25
Q

Describe the general characteristics of the adaptive immunity

A 
Is stimulated once innate system has been overwhelmed
More specific
Has memory 
Mediated by lymphocytes
Two branches: humoral and cell mediated
26
Q

How is communication permitted between the innate and adaptive immune system

A

Via DCs and macrophages

27
Q

List the characteristics of humoral immunity

A

Antibody mediated
Acts against extracellular invaders
Produced by B lymphocytes

28
Q

List the characteristics of cell mediated immunity

A

Lymphocytes kill infected cells
Act against intracellular invaders
Cytotoxic T cells involved

29
Q

Define somatic cell recombination

A

Multiple gene segments are combined and recombined to form variations in protein binding of antigen

30
Q

What is the action of antibodies

A

Activate complement
Trigger phagocytosis
Neutralise viruses and toxins
Agglutination

31
Q

List the classes of antibody isotypes

A 
IgG
IgA 
IgM 
IgE
IgD
32
Q

Describe each antibody isotype

A

IgG - monomer, most abundant in SERUM: long term immunity and can cross the placenta

IgA - monomer in serum and dimer in secretions, most abundant overall: found in saliva, mucosal surfaces, nasal fluids

IgM - pentamer and involved in primary response; first aby to appear during an infection

IgE - monomer, binds mast cells basophils and eosinophils causing granule release: anti-parasitic and allergy responses

IgD - monomer, attached to B cells and is the largest antibody

33
Q

Describe the primary immune response

A

Has a lag of several days for B cell proliferation
Antibody levels peak and falls as the antigen is removed
The predominant antibody isotype: IgM

34
Q

Describe the secondary immune response

A

Second exposure to the same antigen
The response is much quicker and larger, with a rapid rise in antibody levels
Memory cells become plasma cells much more quicker
Predominant antibody isotype: IgG

35
Q

Define clonal selection

A

How a B or T cell is selected to destroy a particular antigen

36
Q

Describe how clonal selection works

A

An antigen can only bind to an antibody specific to it, the antigen will select the antibody

The specific antigen binds to the variable region on the B cell surface

The B cell is stimulated

Clone is selected

Other antibodies on other B cells are not able to bind

37
Q

Describe cell-mediated immunity

A

Mechanism acting against intracellular infections (viruses, mycobacteria) and cancer cells

T cells involved: Cytotoxic T cells which require T help cells

38
Q

Describe the mechanism of cytotoxic T cells

A

Have a wide range of surface receptors against an antigen
Each Tc is specific for one receptor
Infected cells will express the antigen on their surface by MHC I
Tc via a T cell receptor binds and destroys the cells expressing the specific antigen with MHC I
Killing occurs by the release of toxic molecules effecting the membrane causing lysis and initiating apoptosis

MEDI2000 - IMMUNOBIOLOGY 2021 (3 decks)

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