Lecture 5 Flashcards

(27 cards)

1
Q

What are the two differentiations of B cells

A
  1. Plasma cells
    * ​Produces low affenity antigen specific antiboides
  2. Memory B cells
  • produce high affinity antigen-specific antibodies
  • These are long-lived plasma cells
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2
Q

What are the 5 main antibodies

A
  • IgA
  • IgG
  • IgM
  • IgD
  • IgE
  • Each have a specialised function - Classified according to their heavy chain
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3
Q

What is the dual biological function of Antibodies

A
  1. Varaible regions - Recognition function
    * Binding of antigen is mediated by variable regions
  2. Constant regions - Effector function
  • Clearance mediated by constant region interacting with effector molecules
  • Effector molecues = Complement and Fc receptors
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4
Q

Describe the structure and role of IgM

A
  1. Monomer - Memebrane bound form serves as a B cell antigen recptor
    * Function: B cell activation

​ 2. Pentamer - present in plasma and scretory fluids

  • first antibody produced during an immune responce
  • Function: Agglutination and complement activation
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5
Q

Describe Agglutination

A
  • When an antibody cross-links multiple antigens producing clumps of antigen
  • Specific antigen binding to IgM and IgG
  • Enhances clearance of pathogen by phagocytosis
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6
Q

How is the classical pathway of complement activated

A
  • Initiated by specific antigens binding to IgG or IgM antibodies
  • leads to conformation change in the heavy regions of the antibodies
  • Exposes multiple binding sites for C1 complement protein - which is the first component of the classical pathway
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7
Q

Describe the structure and function of IgG antibody

A
  • Most abundant antibody in serum - 80%
  • This antibody is produced during a secondary/memory immune responce ​​
  1. Functions
  • •Agglutination
  • •Complement system activation
  • •Foetal immune protection
  • •Neutralisation
  • •Opsonisation
  • •Natural Killer cell activation
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8
Q

How does IgG take part in foetal immune protection

A

Transport via placenta directly into foetal blood circualtion

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9
Q

Describe neutralisation by antibodies

A
  • For specific antigen binding to antibody- protective mechanism
  • IgG and dimeric IgA
  • Function:
  1. Protects pathogen from infecting host
  2. Prevents pathogen toxins from disturbing normal cellular function
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10
Q

Describe opsonisation by antibodies

A
  • Antibody coats spefici antigens
  • Constant region of heavy chains Bind to Fc receptor on macrophage
  • Enhance phagocytosis
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11
Q

How do antibodies enhance NK cell activity

A
  • Infected host cells or apoptotic cells express
  • IgG antibodies on surface
  • Binds to Fcy receptor on Natural killer cells
  • Leads to cell killing and release of IFNY which enhances phagocytes
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12
Q

Describe the structure and function og IGD antibodies

A
  • Membrane bound form - B cell activation
  • secreted form in low levels in plasma and function is not well understood
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13
Q

Describe the structure and function of IgA antibodies

A
  • Second most abdundant
  1. Monomeric form - in serum - B cell activation
  2. Dimeric form - found in secratory fluids
  3. Secreted IgA:
  • ​Neonatal defence
  • Neutralisation
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14
Q

Describe the structure and function of IgE antibodies

A
  • Tiggering allergic responces
  • Asthma, allergy anaphylaxis
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15
Q

When are the different antibodies produced during the adaptive immune responce

A
  • IgM is the main produce early one in the reponces to antigen
  • IgG and others are produced later on
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16
Q

How are antibodies of the same specificity, but different Ig classes produced?

A
  • During B cell activation, B cells can change the gene segments of heavy chain constant region
  • process if induced by specific cytokines
17
Q

What are the effector functions of activated CD4+ T cells

18
Q

What are the different T effector cells and whats their function

19
Q

How do T effector cells stimulate other Immune cells

20
Q

How do Effector T cell help T cell responces?

A

They secrete Interleukin-2 (IL-2) – this a cytokine which stimulates proliferation and differentiation of antigen-activated T cells (and antigen-activate B cells)

21
Q

How do effecto T cell stimulate macrophages

A
  • Effector TH1 cells migrate from secondary lymphoid tissues into infected tissue sites.
  • TH1 cells are re-activated by tissue-resident macrophages in an antigen-specific manner
  • TH1 cells express co-stimulatory molecules (e.g. IFNy) that hyper-activate macrophages, enhancing their killing activities and pro-inflammatory cytokine production.
22
Q

How do Effector T cells help B-cells

A
  • Protein antigen bound to BCR is internalised by the B cell
  • Antigen is degraded and peptides are presented on the B cell surface in complex with MHC-II
  • Effector TFH cells move into B cell zone of the lymph node where they are re-stimulated by B cells in an antigen-specific manner and start to express co-stimulatory molecules
  • Re-activated effector TFH cells stimulate the B cell to clonally proliferate
  • •The re-activated Effector TFH cells secrete cytokines that further activate the B cell and stimulate the Germinal Centre response
23
Q

What are the germinal center responces

A
  • B cell proliferation
  • Differentiation into plasma cells
  • Differentiating into memory B cells
  • Ig Heavy chain class switching
  • Generation of high affinity antibodies
24
Q

What are the effector functions of CD8+ T Cells

A

CD8+ cells → Cytotoxic T Lymphocytes (CTLs)
→ Kill infected host cells

25
How do CTLs kill infected hosts
**Exit lymph nodes - enter site of infection - recognise and kill infected tissue cells in an antigen-specific manner**
26
Describe the killing process by CTLS
1. **Release of lytic grangules containing** * **​Perforin -** forms a pore in target membrane * **Granzyme - Serin proteases** triggers Apoptosis * **Granulosin - Induces apoptosis** **​ 2. Fas-ligand mediated killing**
27
Restoring immune system back to Homeostasis