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Semester 2 Molecular Medicine > Antibodies > Flashcards

Antibodies Flashcards

1
Q

What are antibodies produced by?

A

B lymphocytes (plasma cells)

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2
Q

Which stem cells produce all of the blood cells?

A

Haematopoietic cells

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3
Q

Where do B cells come from?

A
  • Stem cells in bone marrow

* Differentiate in the central organs

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4
Q

Where do T cells come from?

A

The thymus

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5
Q

Where are B cells that haven’t met their antigen located?

A

• From blood to peripheral lymphoid tissues

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6
Q

Where is the main site of antigen encounter?

A

Peripheral lymphoid tissues

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7
Q

How do recirculating B cells enter back into the blood stream?

A

Thoracic duct

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8
Q

Describe the structure of a lymph node

A

• Cortex:
- Outer section of B cells organised into follicles
- Paracortical area of T cells and dendritic cells
• Medulla:
- Macrophages
- Antibody secreting cells= plasma cells

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9
Q

What forms during an immune response?

A

Germinal centres of B cell proliferation in the cortex

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10
Q

Where do lymph enter the lymph nodes?

A

Afferent lymphatic vessel

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11
Q

Where do B cells enter the lymph node?

A

Artery

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12
Q

What causes swelling in the lymph nodes?

A

The growing germinal centres of B cell proliferation

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13
Q

What makes up the red pulp in the spleen?

A

Site of RBC destruction

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14
Q

What is white pulp in the spleen?

A

Lymphoid

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15
Q

How do antigen enter the spleen?

A

From the blood stream

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16
Q

What are the basic features of antibodies?

A
  • Expressed as membrane bound (B cell receptor) or secreted forms
  • B cells express a single Ab specificity only
  • Ab have 2 separate functions
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17
Q

What are the 2 functions of Ab cells

A
  • Firstly to bind to the pathogen that elicited its production
  • Secondly to recruit other cells and molecules that will lead to clearance or destruction of the pathogen
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18
Q

Describe the structure of an antibody

A
  • 2 identical heavy chains that are disulfide bonded to each other
  • 2 light chains
  • Each H chain is also disuldfide bonded to an L chain
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19
Q

What are the types of L chain

A
  • Lamba or kappa

* Ab either has one or the other

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20
Q

Which is the more common L chain?

A

Kappa

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21
Q

What are the 2 ways to cleave an antibody?

A
  • Proteolytic by papain: 2 FAB regions

* Proteolytic by pepsin: F(‘ab)2

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22
Q

Where is the binding site for the antigen?

A

In the FAB region

23
Q

What is the Fc region?

A

• Interact with receptors

24
Q

Describe the hypervariability of antibodies

A
  • 3 hypervariable loops

* Determine antigen specificity by forming a surface complimentary to the antigen

25
Q

What determines the final specificity of the antibody?

A

Combination of loops from H and L chains

26
Q

What limits the number of antibody specificities?

A

The number of B cells present

27
Q

Germline theory

A

Separate gene exists for each Ab - not correct

28
Q

Somatic Diversification theory

A

Repertoire is generated from a limited number of V region genes that undergo alteration

29
Q

Chromosomal rearrangement

A

The sequence of a V region is generated by the somatic recombination of separate gene segments

30
Q

Regions in Heavy chains

A
  • Variable
  • Dregion
  • J regions
  • Constant
31
Q

What happens in chromosomal rearrangement

A
  • Somatic mutation, VDJ come together (light and heavy chain)
  • Multiple V regionsand junction and D regions and multiple constant regions
  • Splicing to each giving potential for diversity
32
Q

What accounts for the variation?

A
  • Chromosomal rearrangement
  • junctional diversity
  • Different combinations of light and heavy chains
  • Somatic Hypermutation
33
Q

Junctional Diversity

A

Gap left in cleavage which allows for an enzyme to come in and insert random DNA

34
Q

Somatic hypermutation

A

Mutations occur in the V regions of the H and L chains

• Some will bind antigen better and these are selected for to expand and secrete antibodies

35
Q

What are the 5 classes of antibodies?

A 
• IgG
• IgM
• IgD
• IgA
• IgE
Defined by the heavy chain
36
Q

Which class of antibody do we have most of

A

IgG

37
Q

What drives allergic response?

A

IgE- sucked out of the blood stream and absorbed by mast cells

38
Q

Which classes can exist as a multimeric form?

A

IgM - pentamers

IgA - dimeric

39
Q

What is special about the dimeric form of IgA

A

Taken up by endothelial cells and moved across

40
Q

Antibodies predominating the plasma

A

IgG and IgM

41
Q

Antibodies in extracellular fluid

A

IgG and monomeric IgA

42
Q

Antibodies in secretions

A

Dimeric IgA

43
Q

Which antibody does the foetus receive by transplacental transfer?

A

IgG

44
Q

Which antibody is mostly near to the epithelial surfaces?

A

IgE - especially gut, lungs and skin

45
Q

Which area of the body is free from Ab?

A

The brain

46
Q

How does an antibody protect against a virus?

A

Blocks binding of the cell to the virus receptor

47
Q

How do antibodies protect against toxins?

A
  • Neutralising antibodies blocks the binding of the toxin

* e.g. tetanus toxoid

48
Q

How do antibodies protect against bacteria?

A
  • Coats bacteria
  • Increases phagocytosis
  • Acts as an opsonin
49
Q

What is a clinical issue of antibody-antigen complexes?

A

Accumulate and can activate the complement pathway

Glomerulonephritis autoimmune diesases

50
Q

Monoclonal antibodies

A
  • Mouse produced B cells immunised with antigen and myeloma (cancer) cell
  • Fuse the cells
  • Grow in a drug containing medium
  • Select for antigen-specific hybridoma
  • Clone selected hybridoma cells
51
Q

What is the problem with monoclonal antibodies? How are they overcome?

A

Mouse so body reacts to them

• humanise them

52
Q

Infliximab

A
  • Anti tumour necrosis Factor
  • Rheumatoid arthritis
  • Ankylosing spondylitis
  • Psoriasis
  • Inflammatory bowel disease
53
Q

Herceptin

A
  • Anti HER2

* Can blck growth and lead to the destruction of breast tumour cells that express high levels of HER2

54
Q

Gleevac

A

Anti-tyrosine kinase

• Effective against chronic myeloid leukaemia

Semester 2 Molecular Medicine (27 decks)

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