Rearrangements of immunoglobulin light chain and heavy chain constant region genes in B-cell malignancies

We analyzed immunoglobulin (Ig) gene rearrangements in 69 patients with B-cell malignancies by Southern hybridization. We used 5 probes which covered JH 5'S mu and S gamma 3 loci of the Ig heavy (IgH) chain gene, and C kappa and kappa de loci of the Ig light (IgL) chain kappa gene, respectively. DNA rearrangements were observed in 68 out of the 69 patients using the JH probe. In 97% (33/34) of patients with non-Hodgkin's lymphoma (NHL), 100% (5/5) of chronic lymphocytic leukemia (CLL), 42% (10/24) of non-T cell acute lymphoblastic leukemia (non-T ALL), and in 0% (0/4) of chronic myelogenous leukemia lymphoid crisis (CML-LBC), the rearrangements were detected by C kappa and/or kappa de probes. Furthermore, the genotype of the light chain was defined by rearrangement patterns of these 2 probes. The by using the 5'S mu-probe, class switch recombinations were detected in 76% (25/33) of NHL, 20% (1/5) of CLL, 17% (4/24) of non-T ALL, and in 0% (0/4) of CML-LBC. Among them, 1 case of IgM NHL and 3 cases of double bearer NHL had rearranged on both IgH alleles by the constant region. The results of this study indicate that genotypes correspond well to phenotypes of B-cell malignancies and that the determination of genotype will be useful for making an exact diagnosis of B-cell malignancies.