b cell activation Flashcards
What happens if a b cell is not stimulated by an Ag?
will die (within 1-2 weeks)
What are the groups of b cell Ag?
Thymus dependent (TD) Ags Thymus independent (TI)Ags
What does TD Ags need for stimulation?
t cell help (cytokines & co stimulation)
What are the types of Thymus independent Ags?
TI 1 Ags
TI 2 Ags
What are the Type I TI Ags?
bacterial cell wall components (e.g. LPS)
not Ag specific (mitogens): polyclonal B cell activators
What are the type 2 TI Ags?
repetitious cell wall components (e.g. polysaccharides, flagellin)
Ag specific
Whata re the signals needed for B cell activation?
Ab binding to Ag
CD40 interacting with CD40L(CD154)
What is needed for Ab binding to Ag?
need crosslinking of mIg
single epitope Ags are not effective
What sends the signal down to the nucleus after the Ab binds to the Ag for a b cell to become active?
Igalpha/Igbeta
What is CD40 ?
signaling molecule on b cells
CD40L is on T cells
cytokines serve as a 2nd signal
What is ITAM?
regions associted with Igalpha/beta that initiate the signaling cascade
When does ITAM start the signaling cascade?
when its phosphorylated
What are BCR co-receptors?
CR2
CD19
CD22
What is the function of CR2?
Complement receptor
What does CR2 bind to?
C3d complement molecule
it is on the microbe
What is the function of CD19?
after CR2 interacts with C3d CR2 activates CD19 to send the signal for cascade
What is the function of CD22?
sends a negative signal to the B cell (turn off bcell)
has an ITIM – immunoreceptor tyrosine phosphate inhibitory motif
What is the function of T cell cytokines?
T cell cytokines can induce and/or inhibit the production
of various isotypes.
What happens to bcells with tcells cytokines?
bcells will still work but not as well
What is the function of IL4?
induces IgE expression especially in the presence og IL 5
