Antigen Recognition

Question 1

Name the steps of Lymphocyte Development.

Answer 1

1. Commitment of progenitor cells
2. Proliferation of progenitor
3. Sequential and ordered rearrangement of antigen receptor genes
4. Selection events
5. Differentiation of effectors

Question 2

What cytokine mainly influences the differentiation of leukocytes and erythrocytes from a multipoint progenitor cell?

Answer 2

IL-7

Question 3

What is your immune repertoire?

Answer 3

Antibodies + TCR + BCR

A person makes more forms of antibodies than all other proteins

Question 4

Describe Clonal Selection.

Answer 4

Gene rearrangements that occur in absence of antigen when the lymphocytes are being made. Each daughter cell has a different receptor. Once an antigen is encountered, it will attach to a specific cell with a receptor and that cell will clone itself.

Question 5

What is Allelic Exclusion?

Answer 5

Only ONE allele for a trait is expressed. This means that if CD8 is expressed, CD4 will not be expressed - mono specificity.

Question 6

What are the 3 major mechanisms for generation of lymphocyte receptor diversity?

Answer 6

Combinatorial diversification
Junctional Diversity
Somatic hypermutation

Question 7

Define Combinatorial Diversification.

Answer 7

There are multiple germline genes with VJ and VDJ somatic recombinations.

Question 8

Define Junctional Diversity.

Answer 8

This is an addition of nucleotides during the process fo DJ or VDJ joining.

Question 9

Define Somatic Hypermutation.

Answer 9

Point mutations occur in fully assembled VJ and VDJ regions during an immune response. This provides a significant source of Ab diversity.

Question 10

Mechanisms that account for immune diversity for BCR and TCRs are identical. What does this mean?

Answer 10

Production of HEAVY chain in B cell is the same mechanism for production of BETA chain in T-cells (VDJ)

LIGHT chain B-cell = ALPHA chain T-cell (VJ)

Question 11

What major mechanism for lymphocyte receptor diversity happens in BCR but not TCRs?

Answer 11

Somatic Hypermutation

Question 12

What are the 3 regions pertinent to heavy chain (BCR) and beta chain (TCR) on the genes?

Answer 12

V - variable region
D - Diversity
J - Joining

D to J
V to DJ rearrangement in combinatorial diversity

Question 13

What are the 2 regions pertinent to light chain (BCR) and alpha chain (TCR) on the genes?

Answer 13

V - variable
J - joining

V to J rearrangement in combinatorial diversity

Question 14

What are the Roles of Recognition Signal Sequences?

Answer 14

Provide recognition sites for recognition enzymes that cut and region DNA

Ensure gene sequences are joined in correct order

Question 15

What enzymes are responsible for VDJ recombination?

Answer 15

RAG1 and RAG2
Initiate V(D)J recombination by introducing double-stranded breaks in the DNA
Resolved by non-homologous end-joining

Question 16

When DNA is cut by the RAG enzyme, it is cut in an asymmetrical manner. Name the sites that result.
What enzymes adds nucleotides to what site?

Answer 16

2 Sites created: N and P

P site is asymmetric, so nucleotides are added by terminal deoxyribonucleotidyl transferase (TdT) to the site.

Question 17

The nucleotides added to the P site in a TEMPLATE manner are known as?

What are N-nucleotides?

Answer 17

P-nucleotides

Once, these are added, the strands are symmetrical. The remaining gap is filled with N-nucleotides (Non-template manner)

Question 18

What is the significance of P and N nucleotides?

Answer 18

These additions lead to further diversity in the 3rd hyper variable region (idiotype).
Junctional Diversity