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Immunology > Humoral Immunity 1 > Flashcards

Humoral Immunity 1 Flashcards

1
Q

What are antibodies?

A

Y shaped molecules expressed by immune cells to target pathogens

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2
Q

How do antibodies work?

A

Antibodies work by preventing bacteria entering by binding to the bacteria docking site or neutralising them

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3
Q

Antibody structure?

A

2 heavy and 2 light chains

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4
Q

How many classes does the heavy chain have and what are they divided into?

A

Heavy chain has 5 classes:γ, δ, α, μ and ε.
These are further divided into 4 subclasses: Y1, Y2, Y3 & Y4.
which can be further divided into alpha-1 or alpha-2

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5
Q

How many domains, constant and variable regions does the heavy chain have?

A

Heavy chain has 4 domains, 3 constant and 1 variable

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6
Q

Describe the variable region and its function?

A

The variable region is very specific and binds to specific epitopes of specific antigens.

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7
Q

How many variables and constant regions does the light chain have?

A

1 variable and 1 constant

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8
Q

How many classes does the light chain have?

A

kappa (κ) chain or lambda (λ) chain

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9
Q

Describe the constant region?

A

The constant region is very responsible for biological activities.

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10
Q

How many forms do antibodies have and what are they?

A

B cell receptor or secreted form.

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11
Q

What is the final form and what is it used for?

A

The final form is the secreted form and is used to fight off pathogens

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12
Q

What is the final form of antibody anchored to?

A

It is anchored to the plasma membrane of B cells

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13
Q

What forms can the antibody be in when secreted?

A

When the antibody is secreted it can be in monomeric or pentameric forms.

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14
Q

In which form are antibodies initially secreted as?

A

As a monomer and then combined to produce a multimeric form

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15
Q

Where do B cells spend their life?

A

B cells spend their life in bone marrow, blood, spleen and secondary lymphoid organs.

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16
Q

What can the life cycle of B cells be divided into?

A

The life cycle can be divided into antigen-dependent and independent stages.

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17
Q

Describe the steps involved in the lifecycle of B cells?

8 Steps

A
  1. Starts with Stem cell which differentiates into pro B cell
  2. Pro B cells undergo VDJ (variable diversity joining) recombination which codes in the heavy chain- constant and variable regions and become a pre-B cell. It can only pre-b cell once it makes a functional heavy chain.
  3. Then it undergoes another VDJ recombination to code in the light variable and heavy chain regions.
  4. B cell continues to mature until it expresses IgM and IgD.
  5. Becomes a mature circulating B cell and then becomes activated once it encounters a pathogen.
  6. B cell migrates into the germinal centre (GC) and will undergo a special selection to hone its variable region to that particular pathogen.
  7. Undergoes affinity maturation and class switching
  8. Differentiates into plasma cells which secrete antibodies and memory B cells
18
Q

What are somatic recombinations and an example?

A

Any changes at the DNA level are called somatic recombination e.g. VDJ recombination

19
Q

What is differential splicing?

A

changes at the mRNA level are called differential splicing

20
Q

What is each chain of antibody made of?

A

Each chain is made of one single polypeptide

21
Q

What is the hinge region between in antibodies?

A

The hinge region is between CH1 and CH2

22
Q

What makes the antibody flex and so what does this expose?

A

These are a stretch of polypeptides that make the antibody flex so that the active site can be exposed

23
Q

What chain is the hinge region longer in?

A

Longer in the heavy chain

24
Q

What are the Fv regions?

A

Variable regions of light and heavy chains working together

25
Q

What are Fab regions?

A

Variable fragment and first constant domains

26
Q

What are the Fc regions?

A

Heavy chain CH2 and CH3 working together

27
Q

What does glycan form a part of and what does it attract?

A

Glycan (sugar group) forms part of the active site and forms a pocket where the receptors of the other immune cells will be attracted to.

28
Q

What stabilises the antibody structure?

A

Disulphide bonds stabilise the structure

29
Q

What are CDRs?

A

Protrusions that interact with the antigens

30
Q

Where are CDRs located in the antibody?

A

They are located in the variable light and variable heavy chains

31
Q

The lifecycle of B cells (Antigen independent stage)

A
  1. Stem cell differentiates into Pro-B cell
  2. Pro-B cell undergoes DNA recombination
    (First, the V region combines with the DJ region- this is VDJ recombination)
  3. This codes for the heavy chain variable region. the heavy chain variable region is co-expressed with μ constant region- constant region for IgM antibody class (this is the default for all B cells before they encounter pathogens)
  4. Pre B cell expresses valid functional chains
  5. This pre B cell expresses a placeholder light chain to hold it in place as light chain is not generated yet.
  6. Undergoes third recombination on the light chain- VJ recombination. codes in the variable and constant regions on light chain.
  7. There are also additional processes such as junctional flexibility and P and N nucleotide addition. This contributes to the diversity of the antibody.
  8. Once B cell can express IgM and IgD ( has capacity to alternatively splice mRNA), it becomes a mature/resting/naive B cell.
32
Q

How many loci are there that encode Ig?

A

There are three genetic loci encoding Ig

  • Two for the light chain: kappa and lambda locus
  • One for heavy chain
33
Q

What chromosome is the lambda and kappa chain found on?

A

In humans, the lambda chain is found on Chr22 and kappa on Chr2

34
Q

What chromosome is the heavy chain found on?

A

The heavy chain is on Chr14

35
Q

What genes regarding antibodies are inherited and not inherited?

A

No antibody genes are inherited and only gene segments are inherited

36
Q

What does arranging gene segments in different combinations generate?

A

Arranging these gene segments in different combinations generate many Ig sequences causing the B cell to be unique.

37
Q

What segments are there in the light chain?

A

In the light chain there is variable and J gene segments

38
Q

What regions are there in the heavy chain?

A

In the heavy, there are V, D and J regions,

39
Q

What do segments code for once they’ve been rearranged?

A

Once they are rearranged at the DNA level, they will code for the CDRs

40
Q

What do the J or DJ regions code for?

A

The J or DJ region codes for CDR3 (3RD CDR) region

Immunology (5 decks)

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