T cell receptor

Definition

The T cell receptor (TCR) is a molecule found on the surface of T cells that is essential for recognizing specific antigens presented by other cells. It plays a crucial role in the adaptive immune response by enabling T cells to identify and respond to pathogens, infected cells, and cancerous cells. TCRs work closely with Major Histocompatibility Complex (MHC) molecules to discern foreign invaders from self-cells and are critical for immune surveillance against tumors.

5 Must Know Facts For Your Next Test

1. T cell receptors are highly specific; each TCR recognizes a unique antigen, allowing for a tailored immune response.
2. TCRs consist of two different polypeptide chains, typically alpha and beta, that form a binding site for the antigen-MHC complex.
3. Unlike antibodies, TCRs do not recognize free-floating antigens; they can only recognize antigens when they are presented on the surface of other cells by MHC molecules.
4. There are two main classes of MHC molecules: MHC class I, which presents to CD8+ cytotoxic T cells, and MHC class II, which presents to CD4+ helper T cells.
5. The diversity of T cell receptors is generated through a process called V(D)J recombination, allowing the immune system to recognize a vast array of potential antigens.

Review Questions

• How do T cell receptors and MHC molecules interact to facilitate an effective immune response?
  • T cell receptors interact with MHC molecules to initiate an immune response. When an antigen is processed and presented on the surface of an antigen-presenting cell by MHC class I or class II, the specific TCR binds to this complex. This binding activates the T cell, enabling it to proliferate and differentiate into effector cells that can eliminate infected or cancerous cells. Thus, the interplay between TCRs and MHC is crucial for detecting and responding to diverse threats.
• Discuss the role of T cell receptors in tumor immunity and how they contribute to immune surveillance.
  • T cell receptors are pivotal in tumor immunity as they enable T cells to recognize and respond to tumor-associated antigens presented by MHC molecules on cancer cells. When a tumor expresses abnormal proteins or mutated peptides, these can be identified by TCRs, leading to the activation of cytotoxic T cells that attack and destroy malignant cells. This process underscores the importance of TCRs in immune surveillance, as they help monitor and eliminate emerging tumors before they can develop further.
• Evaluate the implications of T cell receptor diversity on the adaptive immune response against infections and cancers.
  • The diversity of T cell receptors generated through V(D)J recombination is vital for mounting effective adaptive immune responses against a wide range of infections and cancers. This diversity ensures that the immune system can recognize various pathogen-derived antigens and mutated proteins found in tumors. A greater variety of TCRs increases the likelihood of identifying and responding to novel threats; however, this also means that some cancers may evade detection if they lack recognizable antigens. Ultimately, TCR diversity is crucial for maintaining a robust defense against both infectious diseases and cancer.

Related terms

Antigen: A substance that the immune system recognizes as foreign, often a part of pathogens like bacteria or viruses, leading to an immune response.

Major Histocompatibility Complex (MHC): A set of cell surface proteins that present peptide fragments of proteins from pathogens or cancer cells to T cells, facilitating their activation.

Cytotoxic T cells:

A subtype of T cells that directly kill infected or cancerous cells by recognizing antigens presented by MHC class I molecules.