A T-cell receptor (TCR) is a molecule found on the surface of T lymphocytes (T cells) that is responsible for recognizing antigens bound to major histocompatibility complex (MHC) molecules. It plays a crucial role in the cellular immune response by activating T cells upon antigen recognition.
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T-cell receptors are composed of two different protein chains, usually referred to as alpha and beta chains.
The specificity of the TCR for an antigen is determined by the variable regions of these alpha and beta chains.
TCRs recognize antigens only when they are presented by MHC molecules on the surface of other cells.
There are two main types of T cells based on their co-receptors: CD4+ T cells which recognize MHC class II molecules, and CD8+ T cells which recognize MHC class I molecules.
The activation of a T cell through its TCR leads to clonal expansion and differentiation into effector T cells.
Review Questions
What are the primary components of a T-cell receptor?
How do T-cell receptors recognize antigens?
What distinguishes CD4+ and CD8+ T cells in terms of their interaction with MHC molecules?
A set of cell surface proteins essential for acquired immune system to recognize foreign molecules.
Antigen-Presenting Cell (APC): A cell that displays foreign antigens complexed with MHCs on their surfaces, such as dendritic cells, macrophages, and B cells.
CD4+: A glycoprotein found on the surface of immune cells like helper T-cells, monocytes, macrophages, and dendritic cells.