•The BCR and the TCR are multi-protein complexes composed
of both variable antigen binding
chains and “invariant” accessory chains.
•The variable Ag binding chains lack substantial
cytoplasmic tails for
signaling; the accessory chains are necessary for 1.) transport of the antigen receptor to the cell surface
and 2.) initiating signaling
following binding of antigen.
•Antigen binding in mature lymphocytes ultimately leads
to activation of
transcription factors which turn on certain genes and turn off inhibitory genes expressed in resting
cells.
•Pre-T and pre-T cell receptors (chapter 7) employ same accessory molecules for signal transduction in
developing T and B
progenitors.