Longo Nancy S, Lipsky Peter E
Repertoire Analysis Group, Autoimmunity Branch, National Institute of Arthritis and Musculoskeletal and Skin Diseases/ NIH, Bethesda, MD 20892-1560, USA.
Trends Immunol. 2006 Aug;27(8):374-80. doi: 10.1016/j.it.2006.06.007. Epub 2006 Jun 30.
B cells have the unique ability to acquire large numbers of point mutations in the variable segment of rearranged immunoglobulin (Ig) genes during a germinal center reaction. It is broadly accepted that somatic hypermutation (SHM) and affinity maturation are required to generate memory B cells and to produce antibodies capable of accomplishing the host defense functions of the humoral component of the adaptive immune system. However, several studies illustrate that low-avidity interactions between antigen and the B-cell receptor can induce deletion, receptor editing and a T-dependent immune response, suggesting that the high-avidity binding of antigen is not essential. If enhanced antigen binding is not essential for immune responses, what is the purpose of SHM? An alternative benefit of SHM might be to enhance the ability of B cells to track antigens expressed by rapidly mutating microorganisms.
B细胞具有独特的能力，即在生发中心反应期间，在重排的免疫球蛋白（Ig）基因的可变区获得大量点突变。人们普遍认为，体细胞高频突变（SHM）和亲和力成熟对于产生记忆B细胞以及产生能够实现适应性免疫系统体液成分宿主防御功能的抗体是必需的。然而，多项研究表明，抗原与B细胞受体之间的低亲和力相互作用可诱导缺失、受体编辑和T细胞依赖性免疫反应，这表明抗原的高亲和力结合并非必不可少。如果增强抗原结合对免疫反应并非必不可少，那么SHM的目的是什么？SHM的另一个好处可能是增强B细胞追踪由快速突变的微生物表达的抗原的能力。
