Rearrangement of Immunoglobulin Light Chain and Heavy Chain Constant Region Genes in Multiple Myeloma

Abstract

We analysed immunoglobulin (Ig) gene rearrangements in 28 patients with multiple myeloma by Southern hybridization method. We used 5 probes which cover Cκ and κ de loci of Ig light chain κ gene, and J_H, 5'Sμ and Sγ3 loci of Ig heavy chain gene. In 11 out of 12 patients with κ-producing myeloma, DNA rearrangements were observed using Cκ probe. Among them, κde region was rearranged in 7 patients and kept germline configuration in 4 patients. In all of 14 patients with λ-producing myeloma, Cκ region was deleted and κ de region was rearranged. 5'Sμ-probe was very useful for detecting class switch recombination, and furthermore by using Sγ-probe together, Sμ-Sγ joining could be detected. In all of 10 patients with γ-producing myeloma, 5'Sμ and Sγ-probes detected the rearranged band of the same size on at least 1 allele, which suggested the presence of Sμ-Sγ joinings. In 8 of 10 patients with Bence-Jones myeloma, 5'Sμ-probe detected rearranged bands and the presence of class switch recombinations were suggested as observed in other Ig secretory myelomas. In other 2 patients with Bence-Jones myeloma, non-functional class switch recombinations were detected. The results of this study indicated that genotypes corresponded well to phenotypes in multiple myeloma, and further analysis in other types of B cell malignancies will be interesting.