Molecular mechanisms behind B cell receptor and antibody diversity

Question 1

Which 3 molecular mechanisms cause antibody diversity?

Answer 1

1- V- (D)- J recombination and V-(D)- J junctional diversity
2- somatic hypermutation
3- Class-switching

Question 2

Define antibody repertoire?

Answer 2

The antibody repertoire refers to the diversity of antibodies produced by the immune system. Each antibody is specific to a unique antigen, and the repertoire encompasses all the different antibodies that the body can generate to recognize a vast array of potential pathogens or foreign substances.

Question 3

Where do B cells originate?

Answer 3

In the bone marrow

Question 4

What is the first antibody expressed by B cells during their partial maturation?

Answer 4

IgM

Question 5

What happens to immature B cells that recognize self-antigens in the bone marrow?

Answer 5

Undergo clonal deletion and are eliminated via apoptosis

Question 6

What is the term for the process that ensures B cells do not react against self-molecules in the bone marrow?

Answer 6

Central tolerance

Question 7

What is the term for the process that eliminates self-reactive B cells in the spleen?

Answer 7

Peripheral tolerance

Question 8

What antibodies are expressed by mature B cells in the spleen?

Answer 8

IgD and IgM

Question 9

Describe the process of B cell maturation from the bone marrow to the spleen. How does the expression of IgM and IgD change during this process?

Answer 9

B cells originate in the bone marrow where they express IgM on their surface as part of the B cell receptor (BCR) and undergo clonal deletion (central tolerance). After leaving the bone marrow, they migrate to the spleen, where they complete their maturation and start expressing both IgM and IgD on their surface and undergo peripheral tolerance.

Question 10

Compare and contrast central tolerance and peripheral tolerance in B cell development. How are these two processes linked in maintaining self-tolerance?

Answer 10

Central tolerance occurs in the bone marrow, where self-reactive B cells are eliminated through clonal deletion before they enter the bloodstream. Peripheral tolerance occurs after B cells leave the bone marrow, primarily in secondary lymphoid organs such as the spleen. In peripheral tolerance, B cells that recognize self-antigens with their mature BCR (IgM/IgD) undergo clonal deletion again. Both processes work together to maintain self-tolerance and prevent autoimmune reactions.