Immunoglobulin heavy variable 2-5 (Ig heavy chain V-II region HE) (Ig heavy chain V-II region MCE)
1_MDTLC 6_ STLLL 11_ LTIPS 16_ WVLSQ 21_ ITLKE 26_ SGPTL 31_ VKPTQ 36_ TLTLT 41_ CTFSG 46_ FSLST 51_ SGVGV 56_ GWIRQ 61_ PPGKA 66_ LEWLA 71_ LIYWD 76_ DDKRY 81_ SPSLK 86_ SRLTI 91_ TKDTS 96_ KNQVV 101_ LTMTN 106_ MDPVD 111_TATYY
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)