Hartley S B, Goodnow C C
Howard Hughes Medical Institute, Stanford, CA.
Int Immunol. 1994 Sep;6(9):1417-25. doi: 10.1093/intimm/6.9.1417.
Transgenic mice carrying a rearranged Ig gene encoding the H chain of a lysozyme-specific antibody were used to examine the effect of antigen binding affinity on elimination of self-reactive B cells. In H chain transgenic mice, B cells expressed surface IgM and IgD composed of lysozyme-specific H chains and many different possible L chains from endogenous L chain genes. Immunofluorescent staining and flow cytometry revealed a distinct subset comprising approximately 1% of spleen B cells that bound lysozyme with a high affinity comparable with the original lysozyme-specific antibody. Additional subsets accounting for a total of 5-6% of spleen B cells bound lysozyme more weakly, with the weakest requiring 10,000-fold higher concentrations of monomeric hen egg lysozyme to attain 50% receptor saturation. When the various B cell subpopulations were allowed to develop in animals expressing lysozyme as a membrane-bound antigen on autologous cells, both low and high affinity lysozyme-binding B cells were undetectable in peripheral lymphoid organs. These findings demonstrate the efficacy with which low affinity self-reactive B cells can be eliminated in vivo, consistent with the notion that this cellular mechanism accounts for the absence of natural IgM antibodies against self antigens on the surface of blood cells. The data also illustrate the potential use of Ig transgenic mice for analyzing and selecting novel receptor-ligand interactions.
携带重排Ig基因（编码溶菌酶特异性抗体的重链）的转基因小鼠被用于研究抗原结合亲和力对自身反应性B细胞清除的影响。在重链转基因小鼠中，B细胞表达由溶菌酶特异性重链和来自内源性轻链基因的许多不同可能轻链组成的表面IgM和IgD。免疫荧光染色和流式细胞术揭示了一个独特的亚群，约占脾脏B细胞的1%，其与溶菌酶的结合亲和力高，与原始溶菌酶特异性抗体相当。另外占脾脏B细胞总数5-6%的亚群与溶菌酶的结合较弱，最弱的需要比单体鸡蛋溶菌酶浓度高10000倍才能达到50%的受体饱和。当各种B细胞亚群在自体细胞上表达溶菌酶作为膜结合抗原的动物中发育时，在外周淋巴器官中检测不到低亲和力和高亲和力的溶菌酶结合B细胞。这些发现证明了低亲和力自身反应性B细胞在体内被清除的效率，这与这种细胞机制解释血细胞表面不存在针对自身抗原的天然IgM抗体的观点一致。数据还说明了Ig转基因小鼠在分析和选择新型受体-配体相互作用方面的潜在用途。
