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YEAR 2 HUMAN BIOCHEMISTRY > Antibodies > Flashcards

Antibodies Flashcards

1
Q

The Immune System: The Cells

What are the 2 catagories of immunity cells? and how are each of these decribed?

A
  1. Innate immunity=rapid response
  2. Adaptive immunity= slow response
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2
Q

The Immune System: The Cells

All cells of the immune system share a common progenitor – What is it?

A
  • The hematopoietic stem cell
  • Multipotent
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3
Q

The Immune System: The Cells

What produces the vast array of ”white blood cells” that make up our immune system?

A

Rounds of differentiation and specialisation

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4
Q

The Immune System: The Lymphoid Lineage

What are the 3 types of cells found in this category?
And where do they all start life?

A
  1. T- cells
  2. B-Cells
  3. NK-Cells

All start life in the bone marrow, receiving signals from stromal cells

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5
Q

The Immune System: The Lymphoid Lineage

Where do T cells mature and what is their function?

A
  • Mature in the Thymus
  • Regulatory and Cytotoxic
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6
Q

The Immune System: The Lymphoid Lineage

Where do B cells mature and what is their function?

A
  • Mature in the Bone Marrow
  • Produce antibodies
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7
Q

The Immune System: The Lymphoid Lineage

Where do NK cells mature and what is their function?

A
  • Mature in the Bone Marrow and also secondary lymphoid tissues
    -Cytotoxic
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8
Q

B-cell development:

What is B-Cell development dependent on?

A

Dependent on the transcription factor Pax5

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9
Q

B-cell development:

The development of the B-cells and the B-cell receptor, involves a complex series of what? And what does this produce?

A
  • Involves a complex series of gene recombination
  • To produce the vast array of antibodies we need
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10
Q

Antibody Development:

When are IgG and IgM detectable by?

A

By around 2 weeks

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11
Q

Antibody Development:

When may detection of IgG and nAb decline by?

A

After 8 weeks

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12
Q

Antibody Development:

What are the 2 theories of antibody development?

A
  1. Instructive theory
  2. Selective theory
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13
Q

Antibody Development:

Who came up with the Instructive theory and give a description of the theory

A

Instructive Theory: Linus Pauling -1940

  • The antigen acts as a template that directs the folding of the unfolded antibody chain
  • So a specific amino acid chain has the propensity to form a variety of antibodies, depending on the antigen present at the time
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14
Q

Antibody Development:

Who came up with the Selective theory and give a description of the theory

A

Selective theory: Macfarlane Burnet, Niels Jerne, David Talmage, and Joshua Lederberg – 1950s

  • The binding site of the antibody is already pre-determined before antigen is even encountered
  • The presence of antigen only affects how much of that specific antibody you get
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15
Q

Antibody development – The Instructive Theory

What does the instructive theory suggest? And is it correct?

A
  • Suggests that if the antibody protein was unfolded and then refolded without antigen present it would lose its affinity
  • The theory was incorrect, and the binding of antigen is dependent on the amino acid sequence
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16
Q

Antibody development – The Selective Theory

What does the selective theory suggest and is it correct?

A
  • Suggests that each antibody producing cell, makes a single kind of antibody. And this commitment is determined before the antigen is even present
  • this theory is correct
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17
Q

Antibody development – The Selective Theory

Each cell has a distinctive base sequence in its DNA, what does this determine?

A
  • Determines the amino acid sequence
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18
Q

Antibody development – The Selective Theory

As the cell matures…What does each antibody producing cell make? What then happens to the cell if it binds to a molecule during foetal development?

A
  • Makes a small amount of cell surface-bound antibody.
  • The cell is killed – therefore preventing B-cells that act against itself
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19
Q

Antibody development – The Selective Theory

Later when the mature cell is activated, what process does it begin to undergo?

A

Begins to undergo clonal expansion when exposed to antigen

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20
Q

Antibody development – The Selective Theory

What does a Heterogeneous cell population equal?

A

Heterogeneous cell population = heterogeneous antibodies

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21
Q

Classes of Antibody

What are the 5 antibody classes?

A
  1. IgA
  2. IgD
  3. IgE
  4. IgG
  5. IgM
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22
Q

Classes of Antibody:

What are the properties of the antibody IgA? and draw its structure

A
  • Found in mucous, saliva, tears and breast milk
  • Protects against pathogens
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23
Q

Classes of Antibody:

What are the properties of the antibody IgD? and draw its structure

A
  • Part of the B cell receptor
  • Activates basophils and mast cells
24
Q

Classes of Antibody:

What are the properties of the antibody IgE? and draw its structure

A
  • Protects against parasitic worms
  • Responsible for allergic reactions
25
Q

Classes of Antibody:

What are the properties of the antibody IgG? and draw its structure

A
  • Secreted by plasma cells in the blood
  • Able to cross the placenta into the fetus
26
Q

Classes of Antibody:

What are the properties of the antibody IgM? and draw its structure

A
  • May be attatched to the surface of a B cell or secreted into the blood
  • Responsible for early stages of immunity
27
Q

Antibody Structure - Heavy and Light Chains

What is Fab and Fc in antibody structure?

A

Fab = Antigen binding Fragment

Fc = Crystallisable region fragment

28
Q

Antibody Structure - Heavy and Light Chains

What is IgG made up of?

A
  • 2 polypeptide chains:

Light Chain x1
Heavy Chain x1
H2L2: Heavy/Light

29
Q

Antibody Structure - Heavy and Light Chains

What is the antibody structure held together by?

A

Held together by disulphide bridge

30
Q

Antibody Structure - Heavy and Light Chains

Both chains consist of what 2 regions? and how many amino acids are in each?

A
  • a variable region and a constant region

Variable= 1 – 108 amino acids
Constant= 109 – C-terminus

30
Q

Antibody Structure - Homologous Domains

Vl and Vh are both what?

A

Very similar

31
Q

Antibody Structure - Homologous Domains

The heavy chain consists of what?

A

3 equal thirds

32
Q

Antibody Structure - Homologous Domains

Where is the intrachain disulphide bond located?

A
  • Located in the same place on every domain of both the H and L chains
32
Q

Antibody Structure – Immunoglobulin Folding

What does this consist of?

A

Broad sheets of anti-parallel β-sheets

32
Q

Antibody Structure - Homologous Domains

What is CL very similar to?

A

The 3 CH domains

33
Q

Antibody Structure – Immunoglobulin Folding

Hydrophobic side chains are tightly packed between the anti-parallel beta sheets. What are they held together by?

A

Held together with disulphide bridges

34
Q

Antibody Structure – Immunoglobulin Folding

What are the constant and variable domains?

A

Constant domains:
3 β-sheets in one strand
4 β-sheets on the other

Variable domains:
2 additional β-sheets
3 loops that compose the part of the antigen binding site

35
Q

Antibody Diversity:

What did William Dryer and Claude Bennett discover in 1965?

A
  • Multiple variable genes
  • 1 Constant gene
  • These genes are separated, and one V becomes joined to the C during differentiation and maturation of the B-cell
36
Q

Antibody diversity:

What did Susuma Tonegawa confirm in 1985?

A
  • Confirmed that V and C genes are far apart in the embryonic DNA
  • And are closely associated in B-cells
  • Immunoglobulin genes are translocated during the differentiation of B-cells
37
Q

Antibody Diversity:

How many different kinds of antibodies can be made by an animal?

A

Number in the millions

38
Q

Antibody Diversity:

What are the several hundred genes for the variable regions of a mouse?

A
  • 300 for the light chain
  • 300 for the heavy chain
  • 9x10^4 different specificities
39
Q

Antibody Diversity:

There is a large discrepancy between the germline variation and adult variation. What does this mean must be generated?

A

Must be an alternate source generated during the lifetimes of an animal and the differentiation of its lymphocytes

40
Q

Antibody Diversity – V(D)J Recombination:

What does the V gene not encode for and when does it stop?

A
  • The V gene does not encode for the entire polypeptide chain.
  • Stops at amino acid 95, 13 residues too short
41
Q

Antibody Diversity – V(D)J Recombination:

Light chain:
Where is the stretch of DNA that encodes for this region found?

A
  • Found nearer the Constant region
  • an array of 4 joining regions
42
Q

Antibody Diversity – V(D)J Recombination:

  • What can happen to 1 of the several hundred V genes?
A

-Can become spliced to one of the 4 Joining genes

-Further diversity added as this splicing can occur in different joining frames

43
Q

Antibody Diversity – V(D)J Recombination

Heavy chain: The heavy chain has an additional region, What is it?

A
  • The D region
    D = Diversity region
44
Q

Antibody Diversity – V(D)J Recombination

How many genes are in the D region?

A

15 genes within this region

45
Q

Antibody Diversity – V(D)J Recombination

What is special about the enzyme deoxyribonucleotidyl transferase and what does it do?

A
  • It is a special polymerase that does not use a template
  • It inserts extra nucleotides between the V and D regions
46
Q

Antibody Diversity – V(D)J Recombination

What does the light and heavy chain consist of?

A

LIGHT CHAIN:
-250 V genes
- 4 J genes
- At least 3 possible joining frames
- 250 x 4 x 3 = 3000

HEAVY CHAIN:
- 250 V genes
- 5 J genes
- 15 D genes
- At least 3 possible joining frames
- 250 x 5 x 15 x 3 = 56,250
- 3000 x 56,250 = 1.7x10^8 possible variations

47
Q

Antibody Diversity – Class Switch Recombination

What do B-cells only produce at the beginning of life?

A

Begin life only producing IgM

48
Q

Antibody Diversity – Class Switch Recombination

What is Class Switching recombination needed for?

A
  • To produce the other types of antibody
49
Q

Antibody Diversity – Class Switch Recombination

Different classes of heavy chains depend on what?

A

The antibody type

G – γ
M - µ
A – α
D - δ

50
Q

The Germinal Centre reaction:

What does somatic Hypermutation result in?

A
  • Results in mutations being introduced into the V region of the heavy chain and light chain

-Altering the affinity of the immunoglobulin for its antigen

51
Q

The Germinal Centre reaction:

In comparison, What happens in Class Switch Recombination?

A
  • The initial heavy‐chain C regions are replaced by another isotype
  • Modifying the effector activity of the immunoglobulin but not its specificity
52
Q

The Germinal Centre reaction:

Where does somatic hypermutation and class switch recombination occur? And what other cell types are required?

A
  • These occur in secondary lymphoid tissues as part of the Germinal Centre reaction
  • Requires other cell types:
    CD4+ T-cells
    Dendritic Cells
53
Q

Practical Uses of Antibodies:

What are 3 practical uses of antibodies and provide examples for each.

A
  1. Staining
    - Microscopy
    - Flow cytometry
    - Western blotting
  2. Antigen Capture
    - ELISA
  3. Drugs
    - Highly specific to the target, so reduced off target effects
    - Chemotherapy
54
Q
A

YEAR 2 HUMAN BIOCHEMISTRY (12 decks)

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