BCRrekombinaatio

BCR rekombinaatio, also known as V(D)J recombination, is a crucial process in the adaptive immune system that generates the diversity of B-cell receptors (BCRs) and T-cell receptors (TCRs). This process occurs during lymphocyte development in the bone marrow and thymus, respectively. It involves the precise cutting and pasting of specific gene segments that encode the variable regions of antibody and TCR molecules. The gene segments are categorized as V (variable), D (diversity), and J (joining) segments, although D segments are only present in the genes encoding BCR heavy chains and TCR beta and gamma chains. During recombination, enzymes known as RAG1 and RAG2 (recombination-activating genes) recognize specific recombination signal sequences flanking the V, D, and J segments. These enzymes then induce DNA breaks, allowing the chosen segments to be joined together. This somatic recombination event creates unique gene sequences, leading to a vast repertoire of antigen-binding specificities. The process is highly regulated and, if errors occur, can lead to the development of autoimmune diseases or lymphomas. The combinatorial diversity generated by BCR rekombinaatio is further expanded by junctional diversity, which arises from the imprecise joining of gene segments, and somatic hypermutation, a process that occurs after B-cell activation.