| The T-cell antigen receptor (TCR) is made up of two nonidentical polypeptide chains: TCRαβ or TCRγδ.
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| The TCR is a heterodimer made up of two nonidentical polypeptide chains (Fig. 36.2). These chains are termed the TcRα, β, γ and δ, and the only functional combinations are αβ and γδ. The structure is based on the immunoglobulin domain (see Chapter 3). Each chain comprises two domains - one constant and one variable amino acid sequence. The antigen-binding site of the TCR is in the cleft formed by the adjoining single N-terminal variable domains of the constituent alpha (Vα), beta (Vβ), gamma (Vγ), or delta (Vδ) chains. The effector function of the constant domain in each of the antigen receptor chains is signal transduction. The two chains come into close contact via the covalent bonds between the variable domains and noncovalent hydrophobic interactions between the opposing faces of the constant domains.
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