Lecture 4 Immune Processes III Flashcards

(25 cards)

1
Q

How is antigen presented to T cells ?

A
  • Via MHC molecules
  • T cell receptors (TCR) binds to antigen presented on MHC
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2
Q

What does MHC stand for?

A

Major Historical-Compatibility group proteins

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3
Q

What is MHC-I expressed by ?

A

All nucleated cells

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4
Q

What is MHC-II expressed by ?

A

Specialised antigen presenting cells

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5
Q

What type of cell and MHC molecules does CD8+ recognise?

A

CD8+ CTLs recognise MHC-I and antigen presented by infected cells

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6
Q

What type of cell and MHC molecule does CD4+ T helper cells recognise?

A

They recognise MHC-II and antigen on Antigen presenting cells

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7
Q

3 Antigen Presenting Cells (APCs)

A
  1. Dendritic cells
  2. Macrophages
  3. B cells
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8
Q

What are dendritic cells function? (5)

A
  1. Professional APCs
  2. Migrate from site of infection to lymphoid tissues
  3. Display antigen to naive helper T cells
  4. Important in triggering a Primary immune response
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9
Q

Function of macrophages as APCs

A
  • Can present antigen but less able to activate naive T cells than dendritic cells
  • important in activation of the secondary immune response
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10
Q

Function of B cells as APC (5)

A
  1. B cells bind antigen via B cell receptor
  2. Receptor and antigen endocytosed
  3. B cells present antigens via MHC II to helper T cells with same epitope recognition
  4. Activated T cell releases cytokines
  5. Cytokines activate B cell to produce memory B cells and plasma cells
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11
Q

What are the 3 major immune responses?

A
  1. Inflammation
  2. Humoral mediated immunity
  3. Cell-mediated immunity
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12
Q

What is humoral immunity

A
  • B cell mediated
  • Antibody-antigen mediated
  • Phagocytosis and complement-mediated killing
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13
Q

Steps involved in clonal selection ?

A
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14
Q

Humoral response (10)

A
  1. Macrophage or dendritic cell phagocytoses pathogen
  2. Antigen processed in macrophage or DC & presented in surface via MHC II
  3. Specific T helper cell recognises processed antigen and binds (aided by CD4 binding to MHC II)
  4. Helper T cell activated
  5. B-cell phagocytoses BCR & antigen, presents antigen on MHC II
  6. Helper T cell recognises antigen present enter by B cell
  7. Cytokines from activated helper T cell fully activate B cell
  8. B cell activated to produce clones of plasma cells and memory B cells
  9. Antibody production from plasma cells
  10. Elimination of pathogen
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15
Q

How do antibodies initiate antigen activation?

A
  1. Neutralisation
  2. Agglutination
  3. Precipitation of soluble antigens

1,2&3 enhance phagocytosis - opsonisation

  1. Complement fixation (activation of complement) e.g. MAC leads to cell lysis
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16
Q

What does opsonisation mean?

A

Enhancement of phagocytosis

17
Q

3 different pathways of complement activation ?

A
  1. Classical
  2. Lectin
  3. Alternative
18
Q

What do all complement activation pathways end with?

A

All routes end with formation of Membrane Attack Complex (MAC)

19
Q

What is classical complement activation pathways?

A

Antibody-activated pathway

20
Q

How do complements kill cells/complement-mediated lysis?

A
  1. Complement bind to antigen-antibody complexes on cell surface
  2. Complement cascade activated
  3. Several complement proteins form Membrane Attack Complex (MAC)
  4. A hole is formed in foreign cell and the cell eventually lyses
21
Q

Cell type in cell-mediated response

A

T cell mediated
CTL for cell mediated, aided by t helper cells

22
Q

What does perforin do?

A

Forms pores in target cell membrane

23
Q

What do granzymes do?

A

Intimate apoptosis in target cell membrane

24
Q

Cell-mediated response (5)

A
  1. Infected cell presents antigen on MHC I to CTL
  2. T cell receptor (TCR) binds presented antigen
  3. CD8 binds to MHC I
  4. CTL cell activated
  5. Perforin-forms pores in target cell membrane and granzymes initiate apoptosis in target cell
25
How do Helper T cells trigger humoral response & supply cytokines to CTL? Bit all over the place basically activated t helper cell releases cytokines
When TCR on T helper cell binds to antigen presented on MHC-II on APC APC release interleukin-1 T helper cell release interleukin-2 and other cytokines which tells T cell to divide and also signal CTL to attack infected cells