Lecture 10

Question 1

How do naive B cells have IgM and IgD BCRs with the same V region?

Answer 1

all the antibodies are determined by the constant region of the heavy chain

Question 2

What is the difference in IgM and IgD concentration of immature vs. mature B cells?

Answer 2

Immature B cells: IgMhigh, IgDlow
Mature naïve B cells: IgMlow, IgDhigh

Question 3

Where does B cell RNA transcription start? Where does it end?

Answer 3

• At the promotor sequence upstream of the rearranged Vh (variable region on heavy chain) region
• at the transcription terminator (TT) sequence after the Cdelta region

Question 4

What are the types of CH (constant region of heavy chain) segments?

Answer 4

• Cμm (membrane) & Cμs (secreted)
• Cδm (membrane) & Cδs (secreted)

Question 5

What is the difference in structure of IgM and IgD?

Answer 5

IgM is rigid, IgD has a large hinge region that gives IgD some flexibility

Question 6

How does the H chain get into the plasma membrane? L chain?

Answer 6

the H chain has a transmembrane region, and the L chain doesnt (just attaches to the H chain)

Question 7

What are three types of defects in B cell function?

Answer 7

• inability to secrete Abs
• ability to secrete IgM but no class switching
• inability to form memory B cells after antigen activation

Question 8

Define amporphic, hypomorphic, haploinsufficient and antimorphs

Answer 8

amorphic: no gene function
hypomorphic: partial loss of gene function/performance
haploinsufficient: haploid dose of gene is not sufficient for normal gene function
antimorphs: act in opposition to normal activity

Question 9

What are the phenotypes of SCID?

Answer 9

T-B-NK-, T-B+NK+, T-B-NK+