Immunoglobulin heavy variable 4-39 (Ig heavy chain V-II region WAH)
1_MDLMC 6_ KKMKH 11_ LWFFL 16_ LLVAA 21_ PRWVL 26_ SQLQL 31_ QESGP 36_ GLVKP 41_ SETLS 46_ LTCTV 51_ SGGSI 56_ SSSSY 61_ YWGWI 66_ RQPPG 71_ KGLEW 76_ IGSIY 81_ YSGST 86_ YYNPS 91_ LKSRV 96_ TISVD 101_ TSKNQ 106_ FSLKL 111_ SSVTA 116_ADTAV
1: V region of the variable domain of immunoglobulin heavy chains that participates in the antigen recognition (PubMed:24600447). Immunoglobulins, also known as antibodies, are membrane-bound or secreted glycoproteins produced by B lymphocytes. In the recognition phase of humoral immunity, the membrane-bound immunoglobulins serve as receptors which, upon binding of a specific antigen, trigger the clonal expansion and differentiation of B lymphocytes into immunoglobulins-secreting plasma cells. Secreted immunoglobulins mediate the effector phase of humoral immunity, which results in the elimination of bound antigens (PubMed:20176268, PubMed:22158414). The antigen binding site is formed by the variable domain of one heavy chain, together with that of its associated light chain. Thus, each immunoglobulin has two antigen binding sites with remarkable affinity for a particular antigen. The variable domains are assembled by a process called V-(D)-J rearrangement and can then be subjected to somatic hypermutations which, after exposure to antigen and selection, allow affinity maturation for a particular antigen (PubMed:17576170, PubMed:20176268)