Question

1. List the two types of TCRs, and discuss the role of each. Which of the two is more common? Which is more specific?

Answer 1

Two types of TCRs ie T-cell receptor are .

T cells like B cells express antigen specific receptors.T cell receptor is a heterodimer and made up of two transmembrane glycoprotein chains alpha and beta .The extracellular portion of each chain have two domains resembling immunoglobulin variable and constant domains respectively.Both chain are glycosylated and connected through interchain disulfide bond.Transmembrane helics of both chain have basic amino acid residues lysine ,arginine and histidine . alpha chains carry two such residues and beta chains have one. Some T cells express a TCR distinct from .This alternative TCR is known as and cells expressing this receptor are known as T cells. alpha beta T cells have both CD4+ and CD8+ coreceptors also but gamma deltaT cells not. Both act as receptor for antigens .alpha beta T cell receptor recognize peptide antigen and gamma delta Tcell receptor recognize phospholipid or glycolipid antigen.

More common T cell receptor is .In normal adult humans , Tcells are found in much lower numbers than cells but their numbers increase as a result of infections.

expressing T cells interact with peptide antigens processed and presented on surface of Antigen presenting cells / target cells.Whereas Tcells react with antigen that is neither processed nor presented by a classical major histocompatibility complex molecules. So receptor is more specific in nature.