334 Immune cell signaling

Describe the function of a kinase and phosphatase

Answer explanation

Kinase - phosphorylates, phosphatase - dephosphorylates

Explain crosslinking

Answer explanation

Crosslinking is the process in which BCRs bind to the same multivalent Ag, thereby linking the BCRs together to stimulate a stronger response

Give examples of clustering of receptors and signalling molecules

Explain the difference between digital and analogue signals

Answer explanation

Digital signals are either on or off, whereas analogue can occur on a spectrum

Define ITAMs

Answer explanation

Immunoreceptor tyrosine-based activation motif - a conserved AA sequence present on the cytosolic side of T and B cells and become phosphorylated by Src family kinases which recruit Syc and ZAP-70 to their SH2 domains upon binding of the BCR or TCR and its ligand

Compare and contrast BCRs and TCRs

Answer explanation

Similarities - both have 2 chains, both have Ag recognition domains, do not contain cytosolic tail, ITAMs in cytosol, no enzymatic activity

Differences - differing amounts of ITAMs, BCR has 2 recognition domains TCR has one, BCR has 2 chains in signalling complex TCR has 6

Which signalling molecules bind ITAMs of BCRs and TCRs?

Answer explanation

TCRs - ZAP-70, BCRs - Syk

Why do BCRs and TCRs have co-receptors? Name some common ones

Answer explanation

BCRs and TCRs have co-receptors to regulate the activation of their corresponding cells. Without them, they may activate inappropriately.

BCRs - CD19, 21, and 81

TCRs - CD4, CD8

Describe the process from Ag binding to end products in both BCRs and TCRs

Answer explanation

Soluble Ag binds to BCRs or Ag on other cells or Ag bound to MHC binds with TCR -> co-receptor binding and clustering -> ITAM phosphorylation by Src -> Syc/ZAP-70 binds to SH2 domains -> PLC-gamma -> downstream IP3 and Ca2+ pathways activated -> AP-1, NFAT, and NFkappaB -> Transcription of genes

Name the 3 pathways after Ag binding

Answer explanation

NFAT, NF-kappaB, and AP-1