Chapter 5: The Generation of Lymphocyte Antigen Receptors

Question 1

Why do we have so many antibodies?

Answer 1

• Increase chance of one antibody being able to bind weakly or strongly to antigen
• BCR (B cell recptor/antibody) binding will activate B-cell to undergo clonal expansion
• Somatic hypermutation results in higher affinity

Question 2

What is class switching?

Answer 2

• First antibody produced in immature B cell is IgM
• IgD is later produced in mature naive B cells
• Other isotypes can be produced by switching IgM constant region

Question 3

Why is BCR able to recognize so many antigens?

Answer 3

• Because complete immunoglobulin genes are generated by somatic recombination of segments
• 2 segments make up the light chain variable region
• 3 segments make up heavy chain variable region

Question 4

How are segments selected for V, D, and J segments?

Answer 4

• Segments are randomly selected leading to enormous number of combinations
• Not all segments will be functional or stable
• Different C regions in heavy = different isotypes

Question 5

What 4 processes leads to diversity of the immunoglobulin repitoire?

Answer 5

• Combination diversity (main)
• Junctional diversity - recomb = adding/subtracting of nucleotides ar joint segments
• Variable heavy and light chain combination diversity
• Somatic hypermutation (after activation of B cell)

Question 6

Do IgM and IgD come from the same mRNA? How are different isotypes produced? How does IgM turn to IgD?

Answer 6

• Derived from same pre mRNA, and both expressed on surface of mature B cell
• Clevage, polyadenylation and splicing makes alternate mRNA
• Spliceosome protein ZFP318 promotes splicing yeilds IgD and only expressed on mature activated B cell

Question 7

What allows for Heavy chains to be processed into transmembrane and secreted Ig?

Answer 7

• Alternative processing allows for transmembrane and sectereted Ig derived from the same heavy chain

Question 8

How are γδ T-cell receptors generated?

Answer 8

• Gene rearrangement

Question 9

How are T-cell receptor gene segments arranged? How do alpha and beta chains recombine?

Answer 9

• Arranged in a pattern similar to that of Ig gene segments and are rearranged by same enzymes
• Alpha chain recombines V,J
• Beta chain recombines V,D,J