Lecture #7

Question 1

B cell maturation in the bone marrow

Answer 1

1. Gene rearrangment 2. Junctional diversity 3. Negative selection Binding of BCR to a self molecule can result in elimination of the B cell or receptor editing

Question 2

Receptor editing is done by

Answer 2

Reactivation of RAG1/2 genes

Question 3

BCR can be either ____ or _____

Answer 3

IgM or IgD

Question 4

Two possible B cell responses

Answer 4

DT (T dependent) The Ag is a peptide, requires Th cell, occurs in germinal centers of lymphoid follicles and produces IgA,G,E

TI (T independent) The Ag can be peptide, lipid, polysaccharide, nucleic acid, Th is not needed, occurs either in lymphoid organs or mucosal surfaces and produces only IgM

Question 5

TD B cell activation

Answer 5

Requires 3 signals 1. Ag binding to BCR 2. CD40-CD40L binding between Th2 and the B cell 3. IL4,6 secreted from Th2

Question 6

Upon activation B cells wil secrete ____ at first for

approx. ____ days

And migrate to _____________ interacting with _______ to induce

__________(4)

Answer 6

IgM

10

Cortical greminal center

fTh cells

Class switching
Proliferation
Affinity maturation
Memory

Question 7

What activates fTh cells?

Answer 7

fDC secreting IL6

Question 8

Affinity maturation

Answer 8

Or somatic hypermutation

Changing of the AA at the tip of the Ab in order to create stonger binding between the Ag and the Ab

Totally random process that may result in a lower affinity binding as well but only the high affinity Abs are chosen by the fDC FcR and by C3b CR3 binding

Question 9

Class switching is cytokine dependent which cytokines induce which class?

Answer 9

INF gamma - IgG

IL5 - IgA

IL4/13 - IgE

Question 10

AID

Answer 10

Activation induced deaminase

Another method in order to increase variability, AID converts cytidine to uracil at switch regions in the DNA, U is not a normal nucleotide in the DNA therefore repair system will be activated and random nucleotides will be inserted instead.

Question 11

Differentiation of plasma cells to memory cells

Answer 11

Plasma cells that were activated by TD mechanism will migrate to the bone marrow to interact with stromal cells

Their interaction will produce long live memory cells by IL6 IL6R interaction, BAFF BCMA interactions and many more

Question 12

Negative costimulation

Answer 12

If enough Ab were produced against a certain Ag, co binding of BCR with another epitope on the Ag and Fc region of a preformed Ab with Fc gamma RIIB will inhibit the B cell from producing more Ab

Question 13

TI1 (B2 cells)

Answer 13

At high Ag conc polyclonal plasma cells are produced

At low Ag conc monoclonal plasma cells are produced

Question 14

TI2 (B1cell)

Answer 14

Marginal zone B cells

Activated by polysaccharide Ag and cytokines secreted from DCs mainlt IL5

Produce pentameric IgM and also IgA