T-cell receptor

T-cell receptor (TCR) is a protein complex found on the surface of T cells, or T lymphocytes, that is responsible for recognizing fragments of antigen as peptides bound to major histocompatibility complex (MHC) molecules. The binding between TCR and antigen peptides is of great importance to the immune system's adaptive division.

Structure

The T-cell receptor is composed of two different protein chains (α and β chain). In 95% of T cells, the TCR consists of an alpha (α) chain and a beta (β) chain (encoded by the TRA and TRB genes, respectively), whereas in 5% of T cells the TCR consists of gamma and delta (γ/δ) chains (encoded by the TRG and TRD genes, respectively). This ratio changes during development and in disease states.

Function

The main role of the TCR is to recognize antigens bound to MHC molecules. This recognition is crucial for T cell activation and subsequent immune responses. The TCR recognizes antigens by binding to the antigen-MHC complex on the surface of antigen presenting cells (APCs). This binding triggers a series of intracellular signaling pathways, leading to T cell activation.

TCR Complex

The TCR complex is composed of the TCR itself, as well as several other proteins that assist in signal transduction. These include the CD3 proteins (γ, δ, ε and ζ chains) and the ζ-chain-associated protein kinase 70 (ZAP-70). The CD3 and ζ chains have immunoreceptor tyrosine-based activation motifs (ITAMs) in their cytoplasmic domains, which are crucial for signal transduction.

See Also

• Antigen presenting cell
• Major histocompatibility complex
• T cell
• Immune system
• Adaptive immune system

References

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