B cell-mediated immunity Flashcards
What is the function of BCR on surface of B cells?
Contains IgM, IgD, Iga, and Igbeta for binding
What is the function of Co-BCR on surface of B cells?
The Co-BCR is Cr2 and CD19 which are cytoplasmic tail receptors that recgonize Iga and Igb leading to the transmission of the first signal in B cell activation
What is the function of HLA Class II on surface of B cells?
Recognition and presentation of extracellular pathogens
What is the function of CD80/86 (B7) on surface of B cells?
Upregulated for Th cells during activation allowing Th to provide the cytokines needed
What is the function of CXCR25 in the migration of mature naive B cells in lymphoid tissue?
Facilitates the migration of b cells to the primary follicle if no antigen present
What is the response of B-2 (follicular) B cells?
re-circulating B cells
What is the response of Marginal zone (MZ) B cells?
Resided in the spleen: blood born polysaccharide Ags
What is the response of B1 cells?
Mucosa- limited ag specificity
How do mature, naive B lymphocytes migrate in the lymphoid tissue?
Travel to secondary lymphoid tissues from primary lymphoid follicles, enter through HEV
If no antigen then migrate to primary follicle via CXCR5 and exit through efferent lymphatic vessels
Competition for FDCs (survival signals), die within a few weeks in absence of antigen
What is the antigen induced first signal in B cells? What ligands interact to contribute to antigen recognition (first signal) leading to activation?
Ag recognition by Migs leading to the cross linking of 2 or more BCRs
- ag bound with C3d recgonized by mIgs and CR2 (CD21) leading to cross linking
Signaling occurs via Iga and Igb cytoplasmic tails and CR2 and CD19= BCR co receptor leading to activation of Syk and B cell phosphorylation
TLR signaling through cytoplasmic domains
How does B cell activation lead to change in chemokine receptors?
Cells begin up-regulating CCR7 allowing for migration towards the T cell zone
How does B cell activation lead to migration in lymph nodes?
After activation by ag B cells migrate in lymph nodes towards T cell zone due to upregulation of CCR7
Begin secreting low levels of IgM= primary response
What is the immune synapse between a B and a T cell?
Co stimulatory signals generated by CD40-CD40L interactinos and adhesion molecules leading to release of cytokines by Th which tells B cells what isotype to switch to and induces AID
Class switching and affinity maturation occur at the same time
How does antigen recognition by T cells lead to second activation signal for B cells?
the Cd40/CD40L leads to the release of cytokines by Th cells
What are the two functions of cytokines released by Th cells?
Induction of class switching in H chain
Augment B cell differentiation and proliferation