摘要：

To examine germ line genes of the heavy chain variable region (V H) that might contribute to formation of antibodies of the NP b family, we have derived cDNA clones from two hybridomas making NP b antibodies. One, B1–8, made an IgM protein and was derived during a primary response; the other, S43, made an IgG 2a protein and was derived during a hyperimmune response. Sequence comparison of the two clones showed that they differed by only 10 bp in the V H region, had very different D segments and had identical J segments (J 2). A set of closely related germ line V H genes was then cloned from a partial Eco RI library of C57BI/6 DNA. By comparing the germ line V H regions to the cDNA V H regions, we identified seven potential candidates for encoding the V H regions of NP b antibodies. The seven V H regions were sequenced, and one V(186-2) contained exactly the DNA sequence found in the clone derived from B1–8. None of the DNA sequence differences that distinguished the S43-derived clone from the B1–8 clone was found in any of the other six germ line genes. Because the S43 sequence was more closely related to the V(186-2) germ line sequence than to any of the other V H genes, we conclude that the differences between the genes resulted from somatic mutation and that the two hybridomas derived their V H regions from the same germ line gene. Certain of the sequenced V H genes contain crippling mutations; the repertoire of germ line V H genes that can contribute to the diversity of antibodies may therefore be less than the total number of genes detectable by hybridization.

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