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POM > Immune response to infection > Flashcards

Immune response to infection Flashcards

1
Q

How does the immune response start?

A

Detection of tissue damage - damage associated molecular patterns DAMP
Detection of pathogenic structures - pathogen associated molecular pattern PAMP (molecular detection of microbes)
Inter-cellular signalling using interleukins
Activation of the innate immune system, non-specific immune response
Communicate with adaptive immune cells
Non-immune cells can produce antimicrobial peptides

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2
Q

How does a response to infection stop?

A

After pathogen is cleared, immune cells undergo apoptosis
Suppressed production of inflammatory cytokines mediated by the same mechanism as immune tolerance

After the cell population contracts and some memory cells form tissue repair and remodelling occurs

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3
Q

What are the four different pathogen niches during infection? Give examples of each

A

Extracellular don’t invade host pathogens - staphylococcus, candida, microbiota, worms
Surface adherent - enteropathogenic and enterohaemorrhagic E.coli sticks to the surface of intestinal wall cells

Intracellular vacuolar - stay within a compartement - salmonella, chlamydia, plasmodium, legionella
Intracellular cytosolic - viruses, Liberia, mycobacterium, burkholderia, TB -break open the compartment they infect and reside in the cytosol

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4
Q

Define innate immunity.

A

Fast acting, first line of defence germ-line encoded receptors so all cells of one lineage have the same receptors
Pre-determined and present at birth
non-specific

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5
Q

What are the physical, humeral and cellular components of the innate response?

A

Physical - skin, mucous, epithelial cells, commensal bacteria
Humoral - complement, lectins (neutralise and opsonise pathogens), pentraxins and antimicrobial peptides
Cellular - Neutrophils, macrophages, dendritic cells, natural killer cells

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6
Q

What are the four roles of the innate immune system?

A

Anaphylatoxins - proteins which can lead to vascular permeability
Chemokines - attract immune cells
Opsonisation - coating of a cell membrane setting it up to be phagocytosed
Membrane attack complex

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7
Q

What organ is the innate humeral response mediated by? What does it produce?

A

Liver
Lectins
Iron chelation proteins - siderocalins
Complement system

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8
Q

What are the three pathways for the complement cascade?

A

Classical pathway – activated by C1 binding to antibodies that have bound to antigens

Lectin pathway – activated by C1 binding to lectin that has bound to microbial carbohydrate structures

Alternative pathway – factor C3 gets directly activated onto the surface of the pathogen

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9
Q

How does a membrane attack complex cause cell destruction?

A

Creates a whole in the cell which can lead to an imbalance of sodium and potassium, disrupting the cell surface tension and causes it to swell and explode due to higher osmolarity

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10
Q

Which cells are involved in the innate immune response?

A

Granulocytes
Natural killer cells
Dendritic cells

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11
Q

Why do innate immune cells have less than 100 possible receptors? What are the four types?

A

Innate immune cells recognise structural patterns thus cells of the same lineage have the same receptor

  • Toll like receptors
  • fc receptors
  • Complement receptors
  • scavenger receptors
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12
Q

What are the first few responders in an infection?

A

Neutrophils first - short lived 6hrs

Followed by macrophages

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13
Q

What happens when naive cells are activated by pathogens?

A

Start secreting cytokines and chemokine

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14
Q

Why is uncontrolled phagocytic activity not good?

A

Leads to:
Granulomas
Excessive inflammation and adaptive immunity
Tissue damage

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15
Q

Where do macrophages come from?

A

From monocytes which circulate for 2-3 days then migrate to tissues and develop into macrophages

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16
Q

What type of response to phagocytes show?

A

Pathogen-type specific

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17
Q

What are macrophages activated by and what is enhanced when they are?

A

Activated by T helper cells

  • phagocytosis and migration
  • cytokine/chemokine production
  • Expression of cell surface molecules
  • antimicrobial activities
  • antigen presentation and T-cel activation
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18
Q

What are interferons and how do they work?

A

Cytokines produced by immune cells and infected cells in response to viruses and gram-negative bacteria
Signals surrounding cells and circulating immune cells
Produce antiviral proteins in response

19
Q

What are the three types of interferons and their roles?

A

Type I and III promote antiviral responses

Type II promote antibacterial immunity

20
Q

What do antiviral genes include?

A

Nucleases
Inhibitors of virus entry and exit
Inhibitors of viral uncoating and replication
Inhibitors of protein translation

21
Q

What immunomodulatory roles do interferons have?

A

Enhanced T-cell responses
Anti-inflammatory actions
Tissue repair

22
Q

What are MHCI and where are they found?

A

Receptor found on all nucleated cells

Give an idea of what peptides are inside the cell

23
Q

What do MHCI molecules interact with and what does this achieve?

A

Interact with cytotoxic T cells and NK cells and detect changes in the cells MHCI

24
Q

Where are MHCII cells found and what is their function?

A

Found on dendritic (APCs) only
Detect peptides outside their cell, once they phagocytose the pathogen they present small sections of its proteins on its surface to be detected by other cells

25
Q

Why do NK cells kill cells without MHCI?

A

All nucleated cells should present MHCI however virus cells and some cancer cells try to evade detection by lack of MHCI molecules so NK cells target these cells

26
Q

What are the humoral and cellular components of the adaptive immune system?

A

Humoral- Antibodies (immunoglobulins) and complement

Cellular- Cytotoxic T cells, T helper cells, T-regulatory cells, B-lymphocytes and plasma cells

27
Q

What are the four cellular effector mechanisms in innate immunity?

A
  • Phagocytosis of microbe into phagosome
  • Phagocyte oxidase which is a reactive oxygen species ROS
  • iNOS -nitric oxidase
  • Cytokines released
28
Q

What are the four soluble mechanisms in humoral immunity?

A 
Complement mediated bacterial destruction 
Lectin-binding to neutralise cell attachment or entry 
Iron chelation (siderocalins) to prevent replication 
Antibiotic like peptides
29
Q

What does IL-12 do? When is it released?

A

Promotes T-cell replication

Produced by APCs when pathogen is detected

30
Q

What is the role of IFN gamma and IL-17 with T cells?

A

Interferon gamma allows a T cell to differentiate into a TH1 cell
It also up regulates MHCII expression
IL-17 converts T cell into Th 17 cell

31
Q

What are the two types of receptors in the adaptive immune response?

A

TCR

BCR - cell surface bound IgM

32
Q

Where can memory cells be found?

A

Lymphoid tissues - lymph nodes, spleen GI mucosa (peters patches), mucosal epithelia, bone marrow

Circulation
T cells - migrate to and from lymphoid tissues constantly
B cells - can differentiate into plasma cells

33
Q

What three things are antibodies good at enhancing?

A

Phagocytosis (opsonisation)
Complement activation
Neutralising pathogen

34
Q

What are the four main functions of T cells?

A

Activate phagocytes
Activate B cells
Directly kill infected cells
Regulate the immune response

35
Q

What are the two functions of B cells?

A 
Present soluble antigen to T cells - can present it 
Produce antibodies (main)
36
Q

Name the three different effector T cells and their defining cytokines

A

Th1: IFN-γ
Th2: IL-4, IL-5, IL-13
Th17: IL-17, IL-22

37
Q

What is the principle target cell of Th1 cells and their immune reaction?
What host defence and role in disease do they have?

A

Macrophages - macrophage activation

Intracellular pathogens - autoimmunity, chronic inflammation

38
Q

What is the principle target cell of Th2 cells and their immune reaction?
What host defence and role in disease do they have?

A

Eosinophils - eosinophil and mast cell activation

Helminths (parasitic) - allergy

39
Q

What is the principle target cell of Th17 cells and their immune reaction?
What host defence and role in disease do they have?

A

Neutrophils - neutrophil recruitment and activation

extracellular bacteria and fungi - autoimmunity and inflammation

40
Q

What is thymic involution ?

A

Thymus stops producing new naive T cells and it shrivels away
Over time the T-cells become activated and change from naive T cells to memory cells

41
Q

Explain the sequence of the immune response

A
  1. Innate immune cells recognise pathogen and become activated
  2. They start secreting cytokines and phagocytose pathogens
  3. Antigen presenting cells move to lymph nodes to find specific lymphocytes
  4. Lymphocytes proliferate and differentiate into specific types
  5. Cellular and humoral specific immune response to pathogen
42
Q

Differences between a primary and secondary antibody response?

A

Primary - peak 2 weeks after infection, smaller peak

Secondary - Higher peak and peaks sooner (1 week)

43
Q

Why are two doses of vaccines given?

A

After re-exposure to an antigen, more plasma cells keep producing protective serum antibodies

POM (42 decks)

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