26 - B CELLS 1 Flashcards
1
Q
what do antibodies promote in humoral immunity
A
pathogen neutralization
opsonization
complement
activation
2
Q
how do Tfh cells activate B cells
A
3
Q
characteristics of B cells
A
4
Q
what happens when B cells enter the lymph node
A
5
Q
how are antigens present in the lymph node
A
6
Q
how are antigens retained in the lymph node
A
- opsonized antigen enters the lymph node
- in the lymph node (subcapsular sinus macrophage) (SCS) express complement factors on their surface
- can bind the complement on the opsonized antigen and retain the antigen in the lymph node
- SCS macrophages retain antigen on their surface in lymph node
these macrophages have low endocytic and degradative activity - some antigens are free floating in the lymph node as well
- B cells that enter lymph node can encounter this Ag -> BCR binds specifically to an epitope on Ag
- Ag can also be transported onto surface of follicular DCs -> this is important for later stages in B cell differentiation
7
Q
how does Ag binding to BCR trigger signaling
A
- BCR binds Ag
- B cell also express co receptors (CD19 and CD21)
- bind complement protein
- not necessary but enhance signaling and activation
- BCR is associated with signaling subunits Igalpha and Igbeta
- these have ITAM motifs that become phosphorylated
- signaling can also occur via the co receptor complex
8
Q
outcomes of signaling
A
- phosphorylation of ITAM motifs on Igalpha and Igbeta
- multiple signaling pathways are activated
main outcomes:
1. TFs are activated
-> gene transcription
2. survival signal
3. cytoskeletal reorganization
endocytosis of BCR-Ag
9
Q
internalization and presentation of Ag by B cell
A
10
Q
what is signal 2 for thymus dependent and thymus independent antigens
A
11
Q
Tfh cells providing help to B cells for signal 2
A
12
Q
what is linked recognition
A
13
Q
summary
A
