ENHANCEMENT AND DESTRUCTION OF ANTIBODY FUNCTION BY SOMATIC MUTATION - UNEQUAL OCCURRENCE IS CONTROLLED BY V-GENE COMBINATORIAL ASSOCIATIONS
ENHANCEMENT AND DESTRUCTION OF ANTIBODY FUNCTION BY SOMATIC MUTATION - UNEQUAL OCCURRENCE IS CONTROLLED BY V-GENE COMBINATORIAL ASSOCIATIONS
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DOI：
10.1002/j.1460-2075.1995.tb07278.x
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发表时间：
1995-06-15
期刊：
影响因子：
11.4
通讯作者：
RITTENBERG, MB
中科院分区：
文献类型：
--
作者：
CHEN, C;ROBERTS, VA;RITTENBERG, MB
我们利用体外饱和诱变模拟体内抗体多样化过程的潜力，研究了体细胞突变对抗体功能的正负影响。将相同的突变引入两种抗磷酸胆碱抗体T15和D16的第二个互补决定区，这两种抗体共享相同的种系VH基因序列。T15在初次应答中占主导地位，且不经历亲和力成熟；D16是在记忆应答中共同占主导地位且经历亲和力成熟的抗体的代表。我们之前报道过，>50%的T15突变体抗原结合能力下降。为了测试这种高频率的结合丧失是T15所特有的，还是适用于其他结合位点的随机点突变的结果，我们分析了D16中的相同突变。我们发现D16也有类似的功能丧失，表明B细胞损耗的可能性同样很高。然而，只有D16显示出体细胞突变可提高抗原结合能力，这应会增强其在记忆应答中的持久性。通过分子建模确定的与半抗原基团接触的残基发生突变并没有提高结合能力。相反，有成效的突变发生在与载体蛋白接触或远离抗原结合位点的残基上，可能通过长程效应增加结合位点的灵活性。针对此类残基进行突变应有助于合理设计改良的抗体。
We examined the positive and negative effects of somatic mutation on antibody function using saturation mutagenesis in vitro to mimic the potential of the in vivo process to diversify antibodies, Identical mutations were introduced into the second complementarity determining region of two anti-phosphocholine antibodies, T15 and D16, which share the same germline VH gene sequence, T15 predominates in primary responses and does not undergo affinity maturation, D16 is representative of antibodies that co-dominate in memory responses and do undergo affinity maturation, We previously reported that >50% of T15 mutants had decreased antigen binding capacity, To test if this high frequency of binding loss was unique to T15 or a consequence of random point mutations applicable to other combining sites, we analyzed the same mutations in D16, We show that D16 suffers a similar loss of function, indicating an equally high potential for B-cell wastage, However, only D16 displayed the capacity for somatic mutation to improve antigen binding, which should enhance its persistence in memory responses, Mutation of residues contacting the haptenic group, as determined by molecular modeling, did not improve binding, Instead, productive mutations occurred in residues that either contacted carrier protein or were distant from the antigen binding site, possibly increasing binding site flexibility through long-range effects, Targeting such residues for mutation should aid in the rational design of improved antibodies.