Identification of the Immunoglobulin Light Chain Alleles in White Leghorn Line 15I₅×7₁

Gregory Pharr and Hui Wang

Background and Objective: Our long-term studies of B-cell development in the bursa of Fabricius now involves the understanding of repertoire development by immunoglobulin gene conversion. This study was conducted to identify the Ig-light chain alleles in the 15I₅ and 71 inbred White Leghorn line used in the cross. Given that the pseudogene variable-region donors differ among the three common alleles of the immunoglobulin light chain and that immunoglobulin-conversion occurs intrachromosomally, the correct identification of pseudogene donors involved in gene conversion events requires the identification of the immunoglobulin light chain allele in the inbred White Leghorn lines 15I₅ and 7₁ used to generate the F1 cross. Materials and Methods: The 2,333 bp germline immunoglobulin light chain gene was PCR amplified from genomic DNA of line 15I₅ and line 7₁ and ligated into a plasmid vector. The variable-region gene segment was isolated from the plasmid vector by restriction endonuclease digestion and evaluated by nucleotide sequencing. Results: The nucleotide sequence alignments with the three common alleles of the immunoglobulin light chain showed that the variable-region gene segment sequence from line 15I₅ was identical to immunoglobulin light chain allele S3 and the line 7₁ sequence was identical to the G4 light chain allele. Conclusion: This information will be critical for future studies to evaluate immunoglobulin gene conversion in the 15I₅×7₁ F1 cross, given the nucleotide sequence variation in the pseudogene variable-region donors between the S3 and G4 immunoglobulin light chain alleles.

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