0429 B cell development

Question 1

Which region of the antibody determines the class of immunoglobulin of an antibody

Answer 1

The constant region of the heavy chain

Question 2

List and briefly describe (1 sentence) the 3 main functions of antibodies in host defence

Answer 2

Neutralisation (Neutralising/inhibiting the biological effect of an antigen). Opsonisation (binding of antibody to antigen and facilitating phagocytosis). Complement activation (activating the fucntions of complement proteins)

Question 3

Where does lymphopoiesis (production of lymphocytes) occur ? Where do newly formed lymphocytes move to?

Answer 3

Lymphopoiesis occurs in the bone marrow. Newly formed lymphocytes move to secondary lymphoid tissues/organs (B to any tissue, t progenitor cells to thymus)

Question 4

Describe the heavy chain recombination process in a developing B cell (when does it happen, when does it finish and what is happening)?

Answer 4

Early Pro B cell (D-J recarrangement). Late Pro B cell (V-DJ rearrangement). Large pre-B cell (VDJ is rearragned and surrogate immunoglobulin is expressed)

Question 5

Describe the light chain recombination process in a developing B cell (when does it happen, when does it finish and what is happening)?

Answer 5

Small pre-B cell (V-J rearrangement). Immature B cell (VJ is rearranged and IgM is expressed on the surface)

Question 6

Does heavy and light chain recombination happen before or after transcription

Answer 6

Heavy and light chain recombination occurs before transcription

Question 7

Which segment of the antibody DNA is being ‘selected’ during mRNA splicing

Answer 7

mRNA splicing removes segments of the DNA which code for Ig, Leaving only one segment that determines the Ig type

Question 8

When does the surrogate Ig Light chain first appear)

Answer 8

During large pre-B cell stage (when Heavy chain recombination stops and light chain recombination begins)

Question 9

Describe the process of allelic exclusion. What is it’s primary function?

Answer 9

Allelic exclusion is the inhibition of genetic rearrangement from the second chromosome following successful rearrangement of the first. It ensures variable regions of a lymphocyte are specific for the same antigen

Question 10

What are the 5 broad fates of a B cell after development

Answer 10

No reactivity to self antigens (circulation and lymph nodes). Receptor editing (rearrangement of light chain). Clonal ignorance (has affinity but cannot bidn to an antigen). Anergy (cannot be activated by antigen). Cell apoptosis/clonal deletion (cell is deleted after development by lysis/apoptosis)

Question 11

What recombination steps determine the type of heavy chain on an anti body

Answer 11

D-J recombination followed by V-DJ recombination

Question 12

What recombination steps determine the type of light chain on an antibody

Answer 12

V-J recombination