T and B cell Receptor Flashcards

3684326107	TCR Structure	αβ - 95% γδ - 5% Extracellular α1 and β1 domains are variable Extracellular α2 and β2 domains are constant There are also transmembrane domains and short intracytoplasmic tails The two TCR chains are connected by a disulfide bond between constant sequences	0
3684346112	Variable domains of TCR	α1 and β1 The variable domains contain 3 hypervariable regions (CDR1, 2 and 3) similar to the variable domains of Igs	1
3684356673	TCR genes	There are four TCR multigene families (one for each of the receptor chains): α, β, γ, and δ The α and δ loci are one chromosome 14 The β locus is on chromosome 6 The γ locus is on chromosome 13 Functional TCR genes are produced by rearrangements of V and J segments in the α and δ chain genes and between V, D, and J in the β and γ chain genes	2
3684384917	Rearrangement- V (D) J recombination	Gene rearrangement for α and β The α-chain DNA undergoes a variable-region Vα-Jα joining The β-chain DNA undergoes two variable region joinings. Dβ to Jβ first and then Vβ to DβJβ T cells express RAG1/2 recombinase enzyme to catalyze V-J and V-D-J joining during TCR-gene rearrangement	3
3684414736	TCR complex: TCR/CD3	TCR associates with CD3, forming the TCR-CD3 membrane complex CD3 is required for the surface expression of TCR CD3 is also required for the initiation of the transduction signals as TCR has a very short intracellular tail that cannot signal	4
3684448193	CD3 complex invariant chains	5 total (γ, δ, ε, ζ and η) that form 3 types of dimers: 1) heterodimer: γε 2) heterodimer: δε 3) homodimer of ζζ (90%) or a heterodimer of ζη γ, δ, and ε have Ig-like extracellular domains, transmembrane domain and intracellular domains The intracellular domains contain immunoreceptor tyrosine based activation motif (ITAM), important for signal transduction (Note: γ, δ, and ε have 1 and ζ and η have 3	5
3684484820	CD4 receptor	CD4 is a monomeric membrane glycoprotein with 4 extracellular Ig-like domains, a transmembrane domain, and a long cytoplasmic tail containing serine (which can be phosphorylated) The extracellular domains of CD4 bind to the β2 domains of class II MHC	6
3684494541	CD8 receptor	CD8 is a disulfide-linked heterodimer αβ. The chains contain a single extracellular domain, a transmembrane domain, and a cytoplasmic tail, containing several phosphorylation sites The extracellular domains of CD8 bind to α3 of class I MHC	7
3684511663	TCR signaling	Engagement of MHC-peptide initiates processes that lead to assembly of signaling complex CD4/8-associated p56LCK phosphorylates ITAMs of zeta chains, create docking site for ZAP-70 ZAP-70 phosphorylates a number of adaptor molecules that recruit components of several signaling pathways Signaling pathways induced by ZAP70 promote T cell activation and differentiation	8
3684530214	Accessory membrane molecules	Accessory membrane molecules bind to other ligands on APC (Note: Tc cells do the same to ligands on target cells) and strengthen adhesion 1) CD28 on Th cells interacts with B7 (CD80/86) on APC. This interaction serves as a costimulatory signal for T cell activation 2) CD2 on Th cells to LFA-3 on APC 3) LFA1 on Th cells to ICAM-1 on APC	9
3684543139	B cell receptor (BCR) structure	Since all mIgs have very short cytoplasmic tails which can not generate a signal, they associate with two Iga/IgB heterodimers with long cytoplasmic tails to form BCR that allows signal generation	10
3684570908	B cell coreceptor	Composed of 3 molecules: 1) CD19 (long cytoplasmic tail) 2) CR2 (CD21, receptor for C3d) 3) TAPA-1 (CD81) CR2 binds to the complement-coated Ag bound to the BCR (C3d/Ag/BCR) that results in the phosphorylation of CD19 to induce signal transduction pathway	11
3684581616	Combinatorial Joining	V(D)J rearrangement brings together multiple germline gene segments that may combine randomly, and different combinations produce different antigen receptors that contributes to the diversity of TCR and BCR	12