title: Identification of a trans-acting function regulation HLA-DR expression in a DR-negative B cell variant.
abstract: Somatic cell hybridizations were performed between an HLA-DR negative variant of a human B lymphoid cell line (B-LCL) and normal unrelated B-LCLs. The HLA-DR codes for polymorphic determinants on a heterodimeric cell surface lymphocyte differentiation glycoprotein. A variant subline which was selected in a single step from a diploid heterozygous DR-1 DR-3 B-LCL had lost expression of both DR-1 and DR-3 and the heretodimer; it has been described earlier. In a fusion with a DR-2 B-LCL, the hybrids expressed DR-2 and reexpressed the DR-1 and DR-3 alleles. Similar results were seen in a fusion with a different normal B-LCL. Hybrid clones from both fusions were tested with a large number of alloantisera and essentially all informative sera showed reexpression. The results show that (1) the variant did not arise by mutations in the structural genes for DR-1 and DR-3; (2) the normal cells are supplying a missing gene product needed for expression of DR; (3) this gene product is capable of acting in trans. Chromosome counts showed that the apparent recessiveness of the variant in the hybrids was not due to chromosomal segregation.
mesh_terms: D001402:B-Lymphocytes; D002460:Cell Line; D003601:Cytotoxicity Tests, Immunologic; D005796:Genes; D005809:Genes, Regulator; D008040:Genetic Linkage; D006680:HLA Antigens / Q000096:biosynthesis / Q000235:genetics*; D006801:Humans; D006822:Hybrid Cells / Q000276:immunology*; D007621:Karyotyping; D011123:Polyploidy
chemical_list: D006680:HLA Antigens