Restricted usage of VH and VX genes by murine monoclonal antibodies against 3-fucosyllactosamine

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Abstract
We are studying the structure and regulation of murine antibodies against the 3-fucosyllactosamine antigenic determinant. Analysis of the sequences of seven BALB/ c IgM,χ; monoclonal antibodies (mAb), obtained from four fusions, indicates that these antibodies exhibit restriction in their usage of VH and VL genes. Based on a combination of mRNA sequences and Southern filter hybridization data, all seven light chains are encoded by Vχ;24B and Jχ;1 gene segments. Complete mRNA sequences of the heavy chains revealed that all seven mAb are encoded by VH441, six antibodies are encoded by JH4 and one uses a Jn3 gene segment. The VH441 gene segment and all seven mAb contain a potential glycosylation site at Asn 58 in complementarity-determining region (CDR)2. In contrast to the similarity of the VH regions, the heavy chain CDR3 segments exhibit considerable heterogeneity. They are encoded by three D segments, they vary in length from 7-9 amino acids and display differences in their deduced amino acid sequences. The VH441 gene segment also encodes antibodies against four other carbohydrate antigens, levan, galactan, dextran and galactosyl globoside. The use of a single gene segment to encode antibodies against five different antigens suggests that the domain encoded by VH441 might be particularly well adapted for forming sites that bind carbohydrate determinants. Glycosylation of CDR2 might contribute to the unique properties of this VH domain.

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