Genetica 85: 45-51, 1991. © 1991KluwerAcademicPublishers. Printed&theNethertands. 45 Allelic variants of rearranged immunoglobulinheavy and light chain genes in hybridoma PTF-02 and parent myeloma S. M. Deyev, D. N. Urakov, A. G. Stepchenko & O. L. Polanovsky V. A. Engelhardt Institute of Molecular Biology, Academy of Sciences of USSR, Vavilov str. 32, 117984 Moscow B-334, USSR Received and accepted28 August1991 Key words: Immunoglobulin genes, Hybridoma, allele's pedigree Abstract The hybridoma PTF-02 secretes an antibody against pig transferrin. Rearranged genes for heavy and light immunoglobulin chains have been studied in the genomes of this hybridoma and in the parent myeloma P3-X63.Ag8.653. The hybridoma was shown to contain three rearranged allelic variants of the heavy chain gene's locus. The gene H2, responsible for synthesis of the heavy chain of the antibody to transferrin, was transmitted in the hybridoma cell from a lymphocyte. Two other genes (H 1and H3) were found both in the hybridoma and parent myeloma genomes. The gene H1 was identified in MOPC21 myeloma, which is a precursor of the X63.Ag8 descendent line. Rearranged k genes were also identified both in the hybridoma and parent myeloma. A functional (K2) gene and a fetal (F) gene appeared in the hybridoma genome from an antigen-stimulated normal lymphocyte. The fetal gene was lost in the course of continuous cultivation of the hybridoma PTF-02 cell line. The gene K 1was transmitted from the myeloma used for fusion. In such a way, the pedigree of rearranged heavy and light chain genes in the hybridoma PTF-02 was established. The results obtained in this work may be relevant to many hybridomas whose immortalizing fusion partner is a MOPC21 derivative, and allow one to identify and isolate functional variable genes to create recombinant constructions. Introduction The maturation of B-cells results in antibody synthesis and is followed by DNA structural rearrangement in the loci of genes for immunoglobulin heavy (H) and light (L) chains. These include VL-JL, DwJH, and DHJH-VH joints and DNA rearrangements in the locus of CH-genes from class to class. Different allelic variants of immunoglobulin genes are yielded from these rearrangements. However, it is difficult to study the allelic variants of immunoglobulin genes in an individual lymphocyte. That is why many immorta- lized plasmacytoma cell lines have been studied until now (Kabat, Wu & Belofsky, 1987). A more com- plicated picture is observed in hybridoma cell lines which are aneuploid (Kohler & Milstein, 1976). Hybridomas are made by fusion of an antigen- stimulated normal lymphocyte with an immortalizing lymphoid cell line (Shulman, Widle & Kohler, 1978). The cells used for fusion with lymphocytes do not produce their own immunoglobulins. Therefore, the only functional immunoglobulin protein secreted by a hybridoma resulting from fusion with immortalizing cells should be from the donor lymphocyte. Non- functional genes from a myeloma may also be prresent in fused cells as was shown by our research in a previous paper (Deyev et al., 1987). The study of immunoglobulin genes in hybridoma cells would make it possible to analyze the structure and express- ion of genes coding for synthesis of antibodies having definite specificity, and eventually to isolate variable genes which would allow one to create recombinant