9: Immune receptors and Signal Transduction 2 Flashcards
what are BCRs
transmembrane form of an antibody
what antibodies are expressed by naive mature B cells
IgM and igD
how are antibodies other than IgM and IgD expressed on B cells
class switching or with memory cells
what are the signaling molecules for BCR
Iga and IgBeta
how are Ig a and IgB linked
disulfide bonds to each other and noncovalent with BCR
what makes Iga and IgB signaling molecules
have ITAMS in cytoplasmic tails
what is better about BCR compared to TCR
has two binding sites
co- receptors for B cells that associate with BCR complex
CD21, CD32, CD 19
which co receptors positively regulate B cell activation
CD21 and 19
What does CD 32 do for B cell activation
has an ITIM for negative regulation of BCR
how do the coreceptors link for BCR
to antibody Fc portion or through complement
Another name for CD 32
FcyRII
signal one for BCR complex
Ag to Ig receptor
signal 2 for BCR
CD 19, 21, 32 for signal 2 and signal transduction
what initiates B cell signaling and what does it cause
BCR- Iga/B complex with phosphorylation of ITAMS
what happens after ITAM phosphorylation in BCR
activation kinases and phosphatases
what controls the cascade of signals from B cell activation
co-receptors
what is the role of second messengers in BCR
activate TFs for effector function
what is effector function of BCR
Ab production
TcFs change B cells from
naive to mature/ active cells
what is activated by Ag binding to a BCR complex
Src-Syk activation
how must ag bind to BCR complex
As cross linked dimers
what is activated by 2 Src- 1 syk activation
PLCy and RAS/ RAC GTP
what transcription factors are activated as a result of BCR activation
NFAT, NF-kB and AP1
what do activated PLCy and RAS turn on in B cell activation
genes for Cell growth, differentiation and survival
what activates Syk in BCR
SRC phosphorylates ITAM of Iga and Ig B that allows SYK activation with SH2 domains
What is activiated by Syk specificaly
PLCy that in turn activates Grb2/SOS thorugh SLP 65
NFAT means
nuclear factor activate T cells
what are examples of Src kinases
Lyn, Fyn, and Blk
what connects Src kinases to plasma membrane
lipid anchors
where do cross liked BCRS go for adaptors and signaling molecules
lipid rafts
what type of domains do Syk kinases have
SH2
what activates Syk tyrosine kinases
Src kinases
what is activated by Syk
BLNK and other adaptor proteins
besides RAS, RAC and PLCy, what else is activated by SYK
BTK, bruton tyrosine kinases.
what pathways do BRC activate
Ras-MAP, PLC and PKC-B
what does IP3 bind to release Ca2+ from ER
IP3R receptor
PLCy activated by Syk leads to
PIP2 hydrolyzed into DAG and IP3
DAG leads to
PKC activation for RAS-MAP resulting in AP-1 and NF-kB
what happens after Ca2+ reaches the level it needs
activates calmodulin-calcineurin pathways
what does calmodulin-calcineurin activate
NFAT
how do TCR and BCR compare
same end result but different starts
what is needed for B cell activation of complement
a complex of CR2, CD 19, and CD 81
what part of complement binds and how
C3d bound to bacteria binds CR2 while the bacteria binds IgM with an antigen
what does the combo of BCR and CR2 complex lead to
enhance B cell activation
what is another name for CR2
CD 21
complement activation is part of what type of immunity
innate immunity
how does C3d become involved with the BCR complex
C3 is cleaved by C3b that binds the microbe then degrades into C3d that remains bound to microbe
BCR recognizes what part of the microbe
Ag
what part of the microbe does CR2 recognize
C3d
what makes up the B cell co-receptor complex
CR2-CD19- CD 81
what does the binding of Cr2 and C3d cause
CD 19 gets moved close to BCR associated kinases
what do BCR kinases do to CD19
phosphorylate the tyrosines
why are do the tails of CD 19 need to be phosphorylated in BCR activation
recruits lyn to amplify BCR so ITAMS of Iga and IgB can be phosphorylated
what does phosphorylated CD 19 activate
Pi3 kinase
what does PI3 kinase do
activates Btk and PLCy for greater activation of B cells
what is important for the immune system to work properly
balance between stimulatory and inhibitory signals
why is B cell activation so tightly controlled
avoid collateral damage in host tissue
what happens without inhibition
uncontrolled inflammation and lymphoproliferation that could lead to self antigens
what runs the inhibitory signaling of lymphocytes
inhibitory receptors and E3 ubiquitin ligases
what is the role of inhibitory receptors
recruit and activate phosphatases to counter kinases from Ag receptors