Tcellereceptor

The Tcell receptor, often abbreviated as TCR, is a complex protein found on the surface of T lymphocytes, a crucial type of white blood cell in the adaptive immune system. Its primary function is to recognize and bind to specific antigen fragments presented by other cells, initiating an immune response. The TCR is a heterodimer, typically composed of an alpha (α) chain and a beta (β) chain, though some T cells express a gamma (γ) and delta (δ) chain. Each chain has a variable region, which is responsible for antigen recognition, and a constant region.

The recognition process involves the TCR binding to a peptide fragment presented within the groove of a major histocompatibility complex (MHC) molecule. MHC class I molecules present antigens derived from intracellular pathogens or self-proteins to cytotoxic T cells (CD8+), while MHC class II molecules present antigens from extracellular pathogens to helper T cells (CD4+). This precise antigen recognition is the cornerstone of adaptive immunity, enabling T cells to distinguish between self and non-self, and to target specific threats. Following TCR binding and activation, T cells proliferate and differentiate into effector cells that can eliminate infected cells or orchestrate broader immune responses. The diversity of TCRs, generated through genetic recombination, allows the immune system to recognize an almost limitless array of antigens.