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Medicine Year 1 - Semester 2 - Part 1 > Antibodies > Flashcards

Antibodies Flashcards

1
Q

How are antibodies produced ?

A

By B lymphocytes

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2
Q

How are lymphocytes produced ?

A

Lymphocytes arise from stem cells in bone marrow and differentiate into B cells in bone marrow and T cells in the thymus.

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3
Q

Describe naive B cells

A

These are B cells that have not met antigen, and circulate from the blood into peripheral lymphoid tissues.

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4
Q

Function of Peripheral lymphoid tissues

A

Main site of antigen encounter

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5
Q

Function of lymphatics

A

Drain tissues of fluid, through the lymph nodes and into the thoracic duct.

Recirculating B cells enter back into the bloodstream by the thoracic duct.

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6
Q

State the main sites of B cells in the body

A

Spleen
Lymph nodes

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7
Q

Lymph node organisation

A

Material draining from the site of infection passes through some regions of B/T cells and varieties of antigen presenting cells.

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8
Q

Germinal centre

A

Accumulation of clonal B cells, which are expanding rapidly in response to an infection.

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9
Q

Describe the spleen

A

Site of B cells

Has :

  • Red pulp
  • White pulp
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10
Q

Red pulp

A

Site of RBC destruction

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11
Q

White pulp

A

Lymphoid

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12
Q

Spleen organisation

Where is antigen coming from ?

A

Antigen is coming through the bloodstream, not the lymphatics (like the lymph nodes)

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13
Q

Describe Secondary response

A

Secondary (memory) response is :

  • faster
  • can produce more antibody
  • does not prevent you from making a response to another antigen.

(multiple antiegns - vaccination)

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14
Q

Function of B cells

A

Form part of the ADAPTIVE immune response, the key features of which are antigen specificity, and memory.

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15
Q

Describe some basic features of antibodies

How can they be expressed ?

A

They can be expressed as membrane bound (B cell receptor)

OR

secreted forms

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16
Q

Describe a key feature of B cell antibodies

A

B cells express a single Ab specificity only

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17
Q

State the functions of antibodies (Ab)

A
  1. Bind to the pathogen that elicited its production
  2. 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 antibodies

A

4 polypeptide chains :

  • 2 identical heavy chains
  • 2 identical light chains
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19
Q

Describe the heavy chains of antibodies

A

Disulphide bonded to each other
Each H chain is also disulphide bonded to an L chain

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20
Q

Describe the light chains of antibodies

A

2 Light chains exist as lambda and kappa
(either lambda or kappa, never a mix)

In humans ratio is 2:1 in favour of kappa

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21
Q

Function of the 2 identical heavy and light chains

A

Results in 2 identical binding sites

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22
Q

Function of the constant region of antibodies

A

Activates the complement pathway

OR

Can assist with processes like phagocytosis

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23
Q

Fab region of antibodies

A

Contains the binding site for the antigen

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24
Q

Function of Fab and F(ab)2 fragments

A

Very useful tools in the lab, ie.e can be used to label cells without inducing the effects of the Fc region.

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25
Q

How are the Fab and F(ab)2 fragments removed

A

Fab - by papaln
F(ab)2 - by pepsin

26
Q

Describe how antigens have specificity

A

3 hyper-variable loops determine antigen specificity by forming a surface complimentary to the antigens.

Final specificity is determined by a combination of loops from H and L chains, not either alone.

27
Q

Germline Theory

A

Suggested that a separate gene existed for each Ab, which was not really the case.

28
Q

Somatic Diversification Theory

A

Proposed that repertoire is generated from a limited number of V region genes that undergo alteration.

Essentially correct.

29
Q

Chromosomal Rearrangement

A

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

30
Q

What are V region genes constructed from ?

A

Constructed from multiple gene segments.

31
Q

Junctional Diversity

A

Errors in DNA replication

Completely random insertion of bits of DNA/nucleotides to make up a fresh DNA.

New loop at the front of antibody

CREATES EXTRA VARIABILITY

32
Q

Name the main methods by which you generate antibody diversity

EXAM Q

A
  1. Rearranging multiple gene segments
  2. Junctional diversity
  3. Different combinations of H and L chains
  4. Somatic Hypermutation
33
Q

When do methods to generate antibody diversity occur ?

A

During B cell development

(happens in bone marrow)

34
Q

Somatic Hypermutation

A

Occurs after B cells have become antigen activated in the lymph node.

Accumulation of random mutations

35
Q

State the 5 classes of antibodies and what they are defined by

A

Defined by the heavy chain

IgG
IgM
IgD
IgA
IgE

36
Q

IgE

A

Sticks on mast cells and causes the allergic responses.

Sequestered away on mast cells.

37
Q

IgA

A

Present in secretions, tears and saliva

Good at being transported across epithelium to get into saliva and tears.

38
Q

IgD

A

The first B cells that come out of the bone marrow tend to always have IgD

39
Q

IgG

A

The most common antibody and most prevalent in the bloodstream.

40
Q

Describe IgG subclasses

A

IgG1 is the body common with up to 10mg per ml in blood.

Note : If IgG is increased –> infection, IgG decreased –> deficiency in immune response

41
Q

Why is IgE concentration low in the blood ?

A

IgE which is very low, because as soon as you make it, it gets sucked out of the bloodstream and sits on muscle cells where its going to be doing its jobs.

42
Q

IgM

A

All B cells initially express a membrane form of IgM (also some IgD).

43
Q

Describe Antibody multimers

A

IgA - dimer in secretion
IgM - pentamer in secretion

44
Q

What antibodies are dimers ?

A

IgA

45
Q

What antibodies are pentamers ?

A

IgM
(can also be a monomer)

46
Q

Function of dimeric form of IgA

A

Enables it to get across an epithelial cell and secreted via a transport mechanism.

47
Q

Where is IgE found ?

A

Mostly near epithelial surfaces, especially gut, lungs and skin.

48
Q

Where are IgG and IgM found ?

A

Predominate in plasma

49
Q

Where are IgG and monomeric IgA found ?

A

MAin isotypes in extracellular fluid

50
Q

Where is dimeric IgA found ?

A

Secretions across epithelia, including breastmilk.

Found in intestinal tract and respiratory tract.

51
Q

Brain

A

Normally free from antibodies, due to blood brain barrier

52
Q

Function of antibodies

A

Blocking binding to virus receptor

53
Q

Opsonisation

A

Enhances phagocytosis into cells for degradation

54
Q

What is high in autoimmune diseases ?

A

High levels of Antibody-Antigen complexes
Ab-Ag complexes

Major cause of glomerulonephritis

55
Q

Function of Ab-Ag complexes

A

Important mechanisms for clearing soluble antigens.
Taken up by phagocytes.

56
Q

Monoclonal Antibodies

A

A powerful tool for research, diagnosis and maybe treatment.

Antibodies of just one specificity.
Grown in LAB.

57
Q

New Biologicals

A

Infliximab
Herceptin
Tocilizumab

58
Q

Infliximab

A

Anti-tumour necrosis factor
(inflammatory mediators)

Used in rheumatoid arthritis
Psoriasis
Ankylosing Spondylitis
Inflammatory Bowel disease

59
Q

Herecptin

A

Anti HER2

Can block growth and lead to destruction of breast tumour cells that express high levels of HER2.

60
Q

Tocilizumab

A

Anti-interleukin 6

Used in Inflammatory conditions
Covid-19

Medicine Year 1 - Semester 2 - Part 1 (51 decks)

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