Immunogenetics 21 : 27%291, 1985 ]m lll Ull O- genetics © Springer-Verlag 1985 Refinement of HLA Gene Mapping with Induced B-Cell Line Mutants B. Spring 1., C. Fonatsch 2, C. Mtiller 1, G. Pawelec 1, J. KOmpf 3, P. Wernet 1, and A. Ziegler ~ 1 Immunology Laboratory, MedizinJsche Klinik, Abt. II, Universit~itTtibingen, D-7400 Ttibingen, Federal Republic of Germany 2 Institut fiir Humangenetik,MedizinischeHochschuleLiibeck,D-2400 Ltibeck,Federal Republic of Germany 3 Institut fiir Anthropologie und Humangenetik, Universit~it Ttibingen, D-7400 Tiibingen, Federal Republic of Germany Abstract. The lymphoma cell line B JAB.B95.8.6 was gamma-irradiated to induce mutations of major histocompatibility complex (MHC) encoded genes. Cloned "wild-type" cells were phenotyped HLA-A1, A2, B 13, B35, Bw4, Bw6, Cw4, DR5, DRw52, DQwl, DQw3, DPw2, DPw4, GLOI*I, PGM3*2-1, and ME1*0 and possessed two apparently normal chromosome 6s prior to mutagenesis. Loss mutants were selected 5 days after 3 Gy gamma-irradiation employing three complement-fix!ng monoclonal antibodies specific for HLA-A2 (T(3101) and Bw4 (TU48, TU109). Fifteen independently arising mutants were isolated and cloned. Typing with monospecific alloantisera and cell-mediated lympholysis revealed the presence of HLA-A1, B35, Bw6, Cw4, DR5, DRw52, DQw3, and DPw4 specificities on all mutant clones. HLA-A2, B13, and Bw4 were absent. Mutants differed in their expression of class II antigens. One group retained DQwl and DPw2, another was DQwl-, DPw2 +, and a third was DQwl-, DPw2-. Karyotyping of the "wild-type" line and selected mutant clones showed that the loss ofHLA specificities correlated with deletions which map the HLA-A and -B loci directly to the distal part of the 6p21.33 region and the class II genes to the region 6p21.33 (proximal) to 6p21.31 (distal) on the short arm of chromosome 6. Address correspondence to: Dr. A. Ziegler,Medizinisch-Naturwissenschaftliches Forschungszentrum, University of Tiibingen, Ob dem Himmelreich7, D-7400 Tiibingen, Federal Republic of Germany. * In partial fulfillmentof Ph.D. thesis requirements. Abbreviations used in this paper: CML, cell-mediatedIympholysis;CTX, cytotoxicity;DBBA, direct bacterial binding assay; EBV, Epstein-Barr virus; GLO, gtyoxalase;IBBA,indirect bacterial binding assay; LU, lytic units; ME1, cytoplasmic malic enzyme; MHC, major histocompatibilitycomplex; MOAB, monoclonal antibody; NADP, nicotinamide-adeninedinucleotidephosphate; PGM3, phos- phoglucomutase isozyme3.