A14 TCR and CD3

Question 1

Antigen Binding Receptors

Answer 1

• PRR • BCR • TCR • Ig

Question 2

Immunoglobulin

Answer 2

Y shaped
Domain structure, 1 domain appr. 110 aa Full size: 160 kDa
4 peptide chains, -S-S- bridges
2 identical, glycosilated heavy chain H chain (55 kDa): α, γ, δ, ε, μ
2 identical, non- glycosilated light chain L chain (25 kDa): κ, λ

Question 3

Antigen Binding Receptors of B cell

Answer 3

C =  Constans domain 
V =  Variable domain 
H = Heavy chain 
L =  Light chain 
Fab = Antigen binding sites 
Fc = Crystallized part

Question 4

TCR

Answer 4

1. γδ T-cell as double negative (DN) cells (CD4- CD8-) to periphery
2. β-chain reorganisation
3. Double positive (DP) T-cell (CD4+ CD8+) and CD1
4. Pre-α-chain
5. Reorganisation
6. CD4+ CD8+ αβ TCR/CD3

• Found on surface of T cells and is responsible for recognizing antigen peptide fragments bound to MHC molecules.
• Structure has 1 variable and 1 constant domain.
• They are heterodimers which increase their variability. Most are αβ and smaller ones are γδ.
• They have only 1 CDR (compatibility determining region)
• Families are the same as the antibody families.
• No mutation after activation, no isotype switching.

Question 5

The TCR/CD3 Complex

Answer 5

• CD3 – Cluster of Differentiation 3
• In immunology, the CD3 T cell co-receptor helps to activate both the cytotoxic T cell (CD8+ naive T cells) and also T helper cells (CD4+ naive T cells).
• It consists of a protein complex and is composed of four distinct chains.
• In mammals, the complex contains a CD3γ chain, a CD3δ chain, and two CD3ε chains. These chains associate with the T-cell receptor (TCR) and the ζ-chain (zeta-chain) to generate an activation signal in T lymphocytes.
• The TCR, ζ-chain, and CD3 molecules together constitute the TCR complex.
• TCR complex: The transmembrane region of the TCR is composed of positively charged amino acids, this allows the TCR to associate with other molecules like CD3, which possess three distinct chains (γ, δ, and ε) in mammals.
• These accessory molecules have negatively charged transmembrane regions and are vital to propagating the signal from the TCR into the cell; the cytoplasmic tail of the TCR is extremely short, making it unlikely to participate in signaling.