Immuno

Question 1

What is the adaptive immune response specific for?

Answer 1

Each invader

The specificity arises from receptors that differentiate friendly bacteria and deadly pathogens via antigens.

Question 2

What are the key cells of the adaptive immune response?

Answer 2

Lymphocytes: B cells and T cells

These cells have unique antigen receptors.

Question 3

What is VDJ rearrangement?

Answer 3

A mechanism to generate diverse antigen receptors

It stands for variability, diversity, and joining.

Question 4

List the four key characteristics of VDJ rearrangement.

Answer 4

• Multiple V, D, and J gene segments inherited
• Random recombination of V, D, and J segments
• Recombination inaccuracy leads to variation
• Random reassortment of two chains

Question 5

What is the B cell receptor (BCR) essentially?

Answer 5

An antibody with a transmembrane part

It attaches to the surface of a B cell.

Question 6

What is the Fab region of the B cell receptor?

Answer 6

Fragment-antigen binding region

There are two Fab regions on every BCR.

Question 7

What determines the class of B cell receptor?

Answer 7

The constant region or Fc region

Examples include IgM or IgD.

Question 8

How does the T cell receptor (TCR) differ from the BCR?

Answer 8

TCR has only two chains and no secreted form

It has an alpha chain and a beta chain.

Question 9

What is the antigen binding site in TCRs?

Answer 9

The variable region (V region)

It only has one antigen binding site.

Question 10

What are hypervariable regions?

Answer 10

Segments of the V region that contribute to diversity

They form the actual antigen binding site.

Question 11

How many V, D, and J gene segments does an individual inherit for B cell heavy chains?

Answer 11

44 V segments, 27 D segments, 6 J segments

More segments exist for T cell receptors.

Question 12

What is the role of recombination signal sequences?

Answer 12

They flank points for DNA rearrangement

They guide the cutting and rearranging of DNA.

Question 13

What are the three parts of a recombination signal sequence?

Answer 13

• Heptamer (7 nucleotides)
• Spacer (12 or 23 nucleotides)
• Nonamer (9 nucleotides)

Question 14

What enzymes are involved in VDJ rearrangement?

Answer 14

• RAG1 and RAG2 (cut DNA)
• Ku, DNA-protein kinase, Artemis (repair DNA)
• DNA ligase IV (join DNA)

Question 15

What does terminal deoxynucleotide transferase (TdT) do?

Answer 15

Adds and removes nucleotides randomly

This process increases receptor diversity.

Question 16

What happens if the heavy or beta chain binds to the surrogate chain?

Answer 16

Signals the cell to proliferate

This occurs in B cells with VpreB and T cells with pre-T alpha.

Question 17

What is created during the random assortment of chains?

Answer 17

A light chain for B cells or an alpha chain for T cells

This follows the heavy or beta chain creation.

Question 18

What is tested after the light or alpha chain rearrangement?

Answer 18

If it binds to the heavy or beta chain

This ensures the cell is not self-reactive.

Question 19

What happens if a cell is self-reactive?

Answer 19

It rearranges the light or alpha chain until genetic material runs out

If it runs out, the cell dies.

Question 20

What is the primary function of the adaptive immune response?

Answer 20

It is highly specific for each invader due to unique receptors that differentiate friendly bacteria from pathogens.

Question 21

What are the key cells of the adaptive immune response?

Answer 21

Lymphocytes - the B and T cells.

Question 22

Where do B cells develop?

Answer 22

In the bone marrow.

Question 23

What process do B cells undergo to generate diverse receptors?

Answer 23

VDJ rearrangement.

Question 24

What is the B cell receptor essentially an example of?

Answer 24

An antibody with a transmembrane part.

Question 25

What are the two types of chains that make up the B cell receptor?

Answer 25

Heavy chains and light chains.

Question 26

What is the fragment of the B cell receptor that binds to the antigen called?

Answer 26

Fab region.

Question 27

What is the constant region of the B cell receptor referred to as?

Answer 27

Fc region.

Question 28

How many Fab fragments are present on each B cell receptor?

Answer 28

Two.

Question 29

What happens to the B cell receptor as the B cell develops into a plasma cell?

Answer 29

It gets secreted as an antibody with the same antigen specificity.

Question 30

How many major types of heavy chains are there in immunoglobulins?

Answer 30

Five.

Question 31

What are the five major types of immunoglobulins?

Answer 31

* IgM * IgD * IgG * IgA * IgE

Question 32

What is the first antibody response made in all immune responses?

Answer 32

Immunoglobulin M (IgM).

Question 33

What percentage of serum immunoglobulin does IgM constitute?

Answer 33

Approximately 4%.

Question 34

What structural form does IgM take when serving as a B cell receptor?

Answer 34

Monomer.

Question 35

When IgM is secreted, what form does it take?

Answer 35

Pentamer.

Question 36

What is the role of the J chain in IgM?

Answer 36

It promotes the polymerization of the pentamer by linking to the cysteines of the Fc regions.

Question 37

What is the valence of secreted IgM?

Answer 37

10.

Question 38

Can IgM be made without T cell help?

Answer 38

Yes.

Question 39

What is the most effective antibody at activating the complement pathway?

Answer 39

IgM.

Question 40

What percentage of serum immunoglobulin does IgG make up?

Answer 40

75%.

Question 41

What is the structural composition of IgG?

Answer 41

Two gamma heavy chains and two light chains.

Question 42

What is the valence of IgG?

Answer 42

2.

Question 43

What are the subclasses of IgG?

Answer 43

* IgG1 * IgG2 * IgG3 * IgG4

Question 44

What is the primary role of IgG in the immune response?

Answer 44

To serve as an opsonin.

Question 45

What is opsonization?

Answer 45

The process by which pathogens are coated with molecules to facilitate phagocytosis.

Question 46

What receptor do phagocytes use to bind IgG?

Answer 46

Fc gamma receptor.

Question 47

What is antibody dependent cell mediated cytotoxicity (ADCC)?

Answer 47

A mechanism by which natural killer cells kill virally infected cells using IgG.

Question 48

What unique ability does IgG have concerning the placenta?

Answer 48

It can cross the placenta.

Question 49

What percentage of serum immunoglobulin does IgA represent?

Answer 49

About 20%.

Question 50

What is the valence of IgA?

Answer 50

2.

Question 51

Can IgA cross the placenta?

Answer 51

No.

Question 52

What is the main antibody found in mucosal sites?

Answer 52

IgA.

Question 53

What form does IgA take in mucosal sites?

Answer 53

Dimer.

Question 54

What is the role of the poly-Ig receptor in IgA transport?

Answer 54

It facilitates the transcytosis of IgA dimers across epithelial cells.

Question 55

What are the two forms of IgA?

Answer 55

* IgA1 * IgA2

Question 56

What important role does IgA play in infants?

Answer 56

It neutralizes pathogens in the gastrointestinal tract via breast milk.

Question 57

What is the primary function of IgE?

Answer 57

To mediate allergic and anti-parasitic responses.

Question 58

What makes up only about 0.004% of total serum immunoglobulin?

Answer 58

IgE.

Question 59

What type of receptors does IgE bind to?

Answer 59

Fc epsilon receptors.

Question 60

What happens when IgE binds to its receptors on mast cells?

Answer 60

It triggers granule release.

Question 61

What is the role of IgD in B lymphocytes?

Answer 61

It signals that they are ready to leave the bone marrow.

Question 62

What percentage of serum immunoglobulin does IgD constitute?

Answer 62

Less than 1%.

Question 63

What is the valence of IgD?

Answer 63

2.

Question 65

What is the role of antigens in the adaptive immune response?

Answer 65

Antigens are unique parts of pathogens that cells of the adaptive immune response differentiate to identify invaders. ## Footnote Antigens trigger specific immune responses through their recognition by lymphocytes.

Question 66

What are the key cells involved in the adaptive immune response?

Answer 66

The key cells are lymphocytes, specifically B cells and T cells. ## Footnote Lymphocytes have unique antigen receptors called B cell receptors (BCR) and T cell receptors (TCR).

Question 67

What process do B cells and T cells undergo to generate diverse receptors?

Answer 67

Both B cells and T cells undergo VDJ rearrangement. ## Footnote This process allows for a massive diversity of antigen receptors.

Question 68

What is somatic hypermutation?

Answer 68

Somatic hypermutation is a process that further enhances the diversity of B cell receptors after activation. ## Footnote It leads to stronger and more specific responses to antigens.

Question 69

What is affinity maturation?

Answer 69

Affinity maturation is the process by which B cells develop stronger and more specific responses to antigens through mutation and selection. ## Footnote This process occurs during the rapid proliferation phase of activated B cells.

Question 70

What are the two general parts of a B cell receptor (BCR)?

Answer 70

The two parts are the variable region and the constant region. ## Footnote The variable region binds antigen, while the constant region determines the antibody class.

Question 71

What triggers the activation of B cells?

Answer 71

Activation occurs when a foreign antigen binds and cross-links adjacent BCRs. ## Footnote This initiates a cascade of events for B cell proliferation and differentiation.

Question 72

What is the role of CD4+ helper T cells in B cell activation?

Answer 72

CD4+ helper T cells bind to presented antigens and express CD40 ligand, triggering B cell activation events. ## Footnote This includes the activation of the enzyme Activation Induced cytidine deaminase (AID).

Question 73

What condition arises from a lack of Activation Induced cytidine deaminase (AID)?

Answer 73

The condition is known as Hyper IgM immunodeficiency. ## Footnote Individuals with this condition have difficulty producing antibodies other than IgM.

Question 74

What is the function of AID in B cells?

Answer 74

AID allows B cells to make cuts in DNA, facilitating class switching and somatic hypermutation. ## Footnote This enzyme is specific to B cells and is crucial for antibody class switching.

Question 75

Describe mismatch repair in the context of somatic hypermutation.

Answer 75

Mismatch repair involves MSH2 and MSH6 proteins fixing DNA by removing uridine and adjacent nucleotides, leading to potential mutations. ## Footnote This process is error-prone and can introduce mutations into the BCR.

Question 76

What happens during base excision repair?

Answer 76

Uracil-DNA glycosylase removes uracil, and random nucleotides may be inserted during DNA replication, leading to mutations. ## Footnote This can also affect the specificity of the BCR.

Question 77

How do mutations in the variable region of BCRs affect antibody affinity?

Answer 77

Mutations can increase or decrease the affinity of BCRs for antigens. ## Footnote Higher affinity BCRs are selected for survival during affinity maturation.

Question 78

What leads to the natural selection of B cells during the immune response?

Answer 78

B cells with higher affinity BCRs survive and proliferate while those with low affinity die out. ## Footnote This mimics natural selection on a cellular level.

Question 79

What occurs to the amount of antigen during the immune response over time?

Answer 79

The amount of antigen decreases as the immune system clears the infection. ## Footnote This reduction promotes the selection of B cells with the highest affinity BCRs.

Question 80

Fill in the blank: The process by which B cells change from producing IgM to IgG, IgA, or IgE is called _______.

Answer 80

class-switching. ## Footnote This process is facilitated by the enzyme AID.