(07) Antibody Diversity

Question 1

• Most b-cells screw it up and don’t get out - what’s the percentage chief?

Answer 1

• 95%

Question 2

What entails the selection of multiple germline genes (1st way)?

What entails H-L chain combinations (2nd way)?

• LOOK AT PICTURES IN IPAD FOR MORE DETAIL ON WAYS 1 and 3

Answer 2

• choosing VDJ segments (each of which has a different type) for heavy chain and VJ for light (only if both of these chains work will the b cell leave the bone marrow)
• heavy chain rearranges independenty of light chain - get various specificity by combining different H and L chains (each with their own variable region rearrangements)

Question 3

(Antibodies - Allelic Exclusion) - the 5th way

• Rearrangement of the antibody gene DNA in a random event which occurs on ____ chromosome(s) for each each light or heavy chains. This is called _____.

What does allelic exclusion assure?

Does it occur for heavy or light chains?

So for example you have a yellow bunny mating with a blue bunny - their offspring can make either blue or yellow - but for each b cell it only chooses one - doesn’t mix them up - thats allelic exclusion

Answer 3

• one, allelic exclusion
• That each individual B cell generates only a single antibody molecule rather thatn expressing the genes from both chromosomes.
• both

Question 4

Why don’t you want a b cell with two different antibodies (blue AND yellow?

Answer 4

• you want to to have high avidity (strong binding) - if you have mutliple antibodies you have low avidity and therefore weaker binding

Question 5

(Rearrangement of Antibody Variable Region Genes)

• The _____ chain gene rearranges first, followed by _____.
• If the first splice even fails, the chromosome may ______.
• Does choice of heavy chain VDJ regions influence choice of light chain V and J?

Answer 5

• heavy, light chain
• attempt to splice further down the gene cluster
• no

Question 6

• _____ proteins/enzymes recognize conserved sequences __________, bend the _______ such that the proteins interact, and _______ the intervening DNA sequences. Animals defincient in Rag activity are _______.

Why?

What are the circular structures calle dthat arve cleaved out?

What do the RAGs recognize on each end?

Answer 6

• RAG (recombination activiated genes), flanking each gene segment, DNA strand, cleave out, severely immunocompromised.

Because they don’t rearrange B and T cell receptors

• signal joints
• RSS, recombination signal sequence

Question 7

(Expression of surface Ig)

• B cells develop in the ____ and are released with rearranged __ genes.

Which two antibodies are found on mature B cells released from the marrow?

• Rearrangment occurs in the ____ of Ag

Answer 7

• bone marrow, Ig
• IgM and IgD
• absence

Question 8

Why is IgM the first antibody produced by B cells?

• IgD is also found on the surface of newly formed B cells due to a ___________
• look at picture - recognize that antigen a goes up really fast the second time cuase it has already seen it once

Answer 8

• it is encoded immediately adjacent to the VDJ genes
• mRNA splicing artifact

Question 9

• What does antibody RNA code for that allows it to lodge itself into membrane
• Which is produced more IgM or IgD?
• Will the binding pocket be different if IgD is made?

Answer 9

• transmembrane regions
• much more IgM
• no it will be identical

Question 10

What will happen to antibodies if they bind to self-antigen in the bone marrow? What is this called?

What if there is no self-reaction?

Answer 10

• they will be deleted, tolerance
• will be released from bone marrow

Question 11

• B cells initially mature in the _____, in the _____ of specific antigenic stimulation
• Where do they go after this?
• B cells that encounter Ag (and ____ help) form foci called ______ that contain proliferating B cells\
• What are b cells called that leave the germinal center, reenter circulation, and secrete Ab called? Where do they sometimes reside?

Where do isotype switching and somatic hypermutation occur? follwoing what?

Answer 11

• bone marrow, absence
• secondary lymphoid tissues - lymph nodes, tonsils, spleen, and Peyer’s patches
• T cell, germinal centers
• plasma cells, bone marrow and spleen
• in the periphery, specific antigen stimulation

Question 12

How long will mature be cell live if i doesn’t get into secondary lymphoid tissue?

How long if it gets into there (but has no antigen interaticeion)

• Mouse bone marrow produces 10*10^6 mature b cells a day - level in periphery stays constant due to cell death. Why does it stay level (3 reasons)

Answer 12

• 2-3 days
• 3-8 weeks
• natural turnover, removal of cells that bind self too strongly, or those that fail to enter lymphoid tissue

Question 13

What happens if a plasma cell receives further activation?

Answer 13

• results in isotype swithcing to secrete IgG or IgA

Question 14

(Late B Stage Cell Development)

• Exposure to antigen in the periphery results in
• activation and cell division
• differentiation into _____
• _______ and ______ (introduces AA changes)
• Selection for receptor specificity with greater affinity (_______)
• Differention into _____

\_\_\_ activation of B cells and subsequent changes in
 DNA (somatic hypermutation and isotype switching) or
 RNA processing (secretion of antibody) in the periphery
 require exposure to antigen (except for gene conversion
 events).

Answer 14

• plasma cells
• class swithcing, somatic hypermutation
• affinity maturation
• memory B cells
• ALL

Question 15

(Germinal center formation)

Germinal centers are specialized areas of _______. If stimulated by _____, the B cells will multiply and start to secrete IgM. They will also undergo ______ and _____ for antigen binding sites in these sites.

Where do Plasma cells migrate to?

How about memory B cells?

Answer 15

• secondary lymphoid organs, antigen specific T cells, somatic hypermutation, selection
• all the other lymphoid organs
• continual re-circulation, bone marrow is popular spot - can live a long time (years)

Question 16

• What brings antigen into the lympphoid organs to interact with T-cells and B cells?
• Which t cells are especially helpful to the replication B cells?

Answer 16

• dendritic cells (after phagocytosing something)
• TH2 (t helper 2)

Question 17

• What are the first things that happen following B cell activation?
• what happens to switch the IgM from membrance to secretory?

Answer 17

• proliferation and conversion to secretory IgM (plasma cell)
• RNA splicing, the membrane binding portions of the code are treated as introns and the S (secretory portion) get spliced in