Lecture 8 - Immunity & B cells and AB's Flashcards
(75 cards)
B cell activation requires what two signals?
- Antigen binding to the B cell receptor
- Th2 cell CD40L binding to the CD40 receptor on a B cell
What is the “third” signal that a B cell receives during activation?
Comes via cytokines, and determines whether the cell differentiates into a memory cell or a plasma cell
In order for antigens to signal B cell activation, what has to happen to the B cell receptors?
They must cross-link (with the antigens)
What is the purpose of having the Ig-alpha and Ig-beta coreceptors?
What is the next couple of steps?
They contain a longer cytoplasmic domain (ITAM) that gets phosphorylated (by Blk, Fyn, or Lyn)
Syk then binds to the ITAMS and is continues signal cascade
In addition to the IgM/Ig-alpha/Ig-beta of the B cell receptor, what other molecules are part of the B cell receptor complex?
Cr2
CD19
CD81
The CR2 molecule of the BCR complex binds to…
C3d o the bacterial cell
What happens after CR2 binds to C3d?
The CD19 molecule’s intracelular domain gets phosphorylated and a signal cascade occurs
Where do we find C3d?
On bacterial surface or bound to immune complexes (Ag/Ab complexes)
What type of B cells are BCR complexes expressed on?
All of them!
Which area of the lymph node has a high amount of proliferation?
The Dark zone of the germinal center
What makes up the mantle zone of the lymph node?
Non activated (naive) B cells
Antigens enter the lymph node via ____. B cells enter via _____.
Antigens = Afferent lymphatics
B cells = HEV’s
Antigen pathway once it gets to the lymph node
Afferent – subcapsular sinus – transport to follicle – binds to Follicular Dendritic Cells
The CR2 domain (yes, the same one that is part of the BCR complex) is also found on which cells?
Macrophages and Follicular Dendritic Cells
B cells are activated in the ______
By what?
paracortex
By a specific antigen that is presented by FDC’s in the T cell area
Antigen activated T cells __________
Antigen activated B cells move to _________
T cells proliferate and differentiate
B cells move to the boundary region and present antigen to effector TFH cells
What is formed when B cells present antigen to effector TFH cells?
Cognate interactions / Cognate pairs
The primary focus for expansion f antigen activated B cells is in the _________
The secondary focus for these cells is in the _________
Medullary cords
Primary follicle
Clonal expansion of the antigen-activated B cells occurs in ______, which creates _______
Primary follicle
Germinal center
Two surface molecules on FDC’s that bind and deal with virus/bacteria. Whats the main function of these?
CR1 and CR2
- CR1 binds to C3b
- CR2 binds to C3d
These bind to intact viruses and hold them at the surface.
Immature B cells (leaving) get what signal from FDR’s?
BFF
(induces maturation)
Somatic hypermutation occurs in the _____
It comes before _____, and that comes before ______
rapidly proliferating germinal center cells
SH -> Selection -> Affinity maturation
Affinity of the antibody will increase over time due to…
affinity maturation
If a B cell contains low affinity surface molecule in the germinal center, it doesn’t receive
survival signals from the FDC’s
…undergoes apoptosis