| Popis: |
The chapter gives an overview of an antigen-specific T-cell receptors and their reactions with complexes formed with major histocompatibility complex proteins. The receptors on the two major classes of lymphocytes, B and T cells, are similar structurally but profoundly different functionally. On B cells, the receptors are immunoglobulins (Ig) embedded in the cell surface as integral membrane proteins. The antigen-specific receptors on T cells (T-cell receptors or TCR) are also Ig-like cell surface integral membrane proteins; their recognition of antigens triggers T cells to exercise a great variety of functions but not to secrete the receptors. The enormous diversity of B- and T-cell receptors arises from the many germline gene segments that encode them; as each lymphocyte matures, different combinations of these segments are joined (combinatorial diversity) and additional variations in sequence are introduced at the junctures (junctional diversity), leading to an immense number of variable domain sequences. The TCR reviewed in this chapter normally recognizes and responds only to the complexes formed between small peptides and a specialized set of proteins encoded by the major histocompatibility complex (MHC). The chapter also discusses the T-Cell Receptor genes, proteins, ligand: peptide MHC complexes and TCR accessory proteins (CD3, CD4 and CD8). |
