Lopez O, Perez C, Wylie D
Facultad de Ciencias Veterinarias, Universidad de Buenos Aires, Argentina.
Immunol Rev. 1998 Apr;162:55-66. doi: 10.1111/j.1600-065x.1998.tb01429.x.
Bovine immunoglobulins are made from genes belonging to a small family of closely related VH genes. In this respect cattle resemble all species of domesticated mammals, which also use one VH family. The family, named BoVH1, is homologous to the mouse Q52 family, and there are no more than 20 genes of this family in the bovine genome. Another feature of bovine heavy chains is the use of long CDR3s, which have an average of 21 codons. It seems that there are several families of long, closely related D genes rich in glycine and tyrosine responsible for this length. Sequences described as targets for mutations in other species can be found in CDR1, CDR2, and the putative D genes. The mutation mechanism starts at some point between late fetal stage and birth and seems to be antigen independent. Diversity seems to be generated by hypermutation, although other mechanisms cannot be discounted at this time. Contrary to humans and mice, which have several VH gene families comprising more than 100 genes, cattle use only a few genes and long CDR3s followed by somatic mutation to generate the necessary diversity to recognize the universe of antigens they will encounter during their life.
牛免疫球蛋白由属于一个紧密相关的VH基因小家族的基因产生。在这方面，牛与所有家养哺乳动物物种相似，它们也使用一个VH家族。这个家族名为BoVH1，与小鼠Q52家族同源，牛基因组中这个家族的基因不超过20个。牛重链的另一个特征是使用长的互补决定区3（CDR3），其平均有21个密码子。似乎有几个富含甘氨酸和酪氨酸的长的、密切相关的D基因家族对此长度负责。在互补决定区1（CDR1）、互补决定区2（CDR2）以及假定的D基因中可以找到在其他物种中被描述为突变靶点的序列。突变机制在胎儿后期到出生之间的某个时间点开始，并且似乎与抗原无关。尽管此时不能排除其他机制，但多样性似乎是由超突变产生的。与人类和小鼠不同，人类和小鼠有几个包含100多个基因的VH基因家族，而牛只使用少数基因和长的CDR3，随后通过体细胞突变来产生必要的多样性，以识别它们在生命过程中将会遇到的各种抗原。
