Immunoglobulin heavy variable 4-34 (Ig heavy chain V-II region ARH-77)
1_MDLLH 6_ KNMKH 11_ LWFFL 16_ LLVAA 21_ PRWVL 26_ SQVQL 31_ QQWGA 36_ GLLKP 41_ SETLS 46_ LTCAV 51_ YGGSF 56_ SGYYW 61_ SWIRQ 66_ PPGKG 71_ LEWIG 76_ EINHS 81_ GSTNY 86_ NPSLK 91_ SRVTI 96_ SVDTS 101_ KNQFS 106_ LKLSS 111_ VTAAD 116_TAVYY
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)