Molecular cloning and structure of the human interleukin 2 receptor gene

We have cloned the IL-2 receptor gene from human genomic DNA libraries using IL-2 receptor cDNA as probe. The genomic DNA segments that hybridized with cDNA were subcloned in M13 phages and their sequences were determined. The nucleotide sequences showed that the IL-2 receptor gene was encoded by eight exons and that the coding region sequences agreed completely with that of the IL-2 receptor cDNA cloned from a cell line derived from adult T cell leukemia (ATL), in which IL-2 receptors are expressed abnormally. The nucleotide sequence of the 5'-flanking region had a putative promotor region, which had some homology with the human IL-2 gene. Transcription initiation sites were clustered about 25 bp 3' to the TATA box as assessed by primer extension analysis. These sites for normal and ATL T cells were the same. Exons 2 and 4 encoding the extracytoplasmic portion had significant homology, suggesting that the two exons are derived by duplication of an ancestral exon. Exon 2 contained six cysteine residues, four of which are conserved at the corresponding positions in exon 4.

Low frequency of somatic mutation in beta-chain variable region genes of human T-cell receptors

We have cloned three pairs of rearranged and germ-line variable region (V beta) genes of the beta chain of the human T-cell receptor from the cell lines ATL2, ATL12, and MT-1 of patients with adult T-cell leukemia (ATL). The pairs were derived from the same (for ATL2 and ATL12) and different (for MT-1) individuals. Comparison of the nucleotide sequences showed no somatic mutation in V beta X ATL2 and beta X ATL12-2. Although one nucleotide change was found in V beta X MT1-1, the possibility of polymorphism was not excluded. These results indicate that the frequency of somatic mutation in the V beta gene of the T-cell receptor is 1/10th or less than that in the immunoglobulin gene. Both alleles of the rearranged T-cell receptor gene were analyzed for ATL12 and MT-1. In both, only one of the two rearranged J beta alleles was an active variable-diversity-joining (V-D-J) complex. The results suggest that allelic exclusion occurs in the T-cell receptor gene.

Absence of gross change in primary DNA sequence during aging process of mice

The possibility of age-associated changes in DNA sequence in terms of amplification and rearrangement was examined in mouse spleen, liver and brain using the method of Southern transfer and filter hybridization. The DNA regions studied were at and around nine cloned sequences, most of which are known to move or amplify in certain situations. No detectable age-associated change, however, was observed in all DNA regions studied. These results suggest that widespread DNA sequence rearrangements or amplifications do not occur during the ageing process in mice.

Preferential rearrangement of the immunoglobulin kappa chain joining region J kappa 1 and J kappa 2 segments in mouse spleen DNA

The V kappa-KpnI family, which constitutes approximately equal to 36% of mouse kappa chain variable region gene (V kappa) segments, conserves the Kpn I site (G-G-T-A-C-C) at the position corresponding to residues 35-37. Using this cleavage site, we were able to assess the relative recombination frequency of the kappa chain joining region gene (J kappa) segments in mouse spleen DNA. The J kappa 1 and J kappa 2 segments were used 2- to 5-fold more frequently than were the J kappa 4 and J kappa 5 segments. The J kappa 3 segment was shown to be incapable of recombining with the V kappa segment. The relative recombination frequency of the J kappa segments did not change significantly by lipopolysaccharide stimulation of normal mouse spleens. The relative frequency of the J kappa usage was unaltered in immune disorders such as in nude (nu/nu), MRL (lpr/lpr), and BXSB mice. Seven V kappa-KpnI-J kappa 1 clones were isolated, and their nucleotide sequences were determined. Two of them were derived from the identical germ-line V kappa segment but differed in the nucleotide sequence of the V-J junction. The maximal number of V kappa germ-line segments was estimated to be less than 300 by statistical calculation.

IgE heavy chain constant region genes in atopic dermatitis and senile erythroderma patients

By Southern hybridization using a genomic DNA fragment carrying a human IgE heavy chain constant region gene (C epsilon) as a probe, we analyzed the organization of human C epsilon genes and their flanking regions in 23 atopic dermatitis and 6 senile erythroderma patients with elevated serum IgE levels, and 6 atopic dermatitis patients with normal IgE levels. On Bam HI, Hind III, and Eco RI digestions, we detected three hybridizable fragments containing three human C epsilon genes, C epsilon 1, C epsilon 2, and C epsilon 3, respectively, in all leukocyte DNAs. These fragments were almost identical in size among patients and healthy donors. Pst I digestion generated a genetic polymorphism. We, however, could find no correlation between this polymorphism and the disorders. It was concluded that among the patients and healthy donors, there was no marked difference in the organization of the functional C epsilon gene and its flanking region containing a class switch region. Our conclusion cannot rule out the presence of genetic abnormalities of this region in some atopic dermatitis patients which are not resolvable by our method. In the course of this study, we found a novel C epsilon-like gene in placenta DNA which differs from the three C epsilon genes commonly present in normal human DNA.

Rat lymphoid cell lines producing human T cell leukemia virus. II. Constitutive expression of rat interleukin 2 receptor

Three rat lymphoid cell lines (TARS-1, TARL-2, and TART-1) (12) transformed by human T cell leukemia/lymphoma virus I (HTLV-I) had rearrangement of the beta chain gene of the T cell antigen receptor, and had integrated proviral DNA from HTLV-I in their genomes. As is the case with adult T cell leukemia (ATL)-derived human T cell lines transformed by HTLV-I, these rat cell lines unequivocally expressed interleukin 2 (IL-2) receptor, as determined by radiolabeled IL-2 binding. By Scatchard plot analysis, one of the cell lines, TART-1, proved to have high affinity receptors (Ka = 1.3 X 10(11)/M and 8.8 X 10(9)/M). Rat IL-2 receptor, not human IL-2 receptor, was expressed on HTLV+ rat cell lines, as demonstrated by the fact that they expressed antigens reactive with monoclonal antibodies (ART-18) against rat IL-2 receptor, but not with anti-Tac antibodies. The collective evidence indicates that the endogenous IL-2 receptor gene is activated in human and rat lymphoid cell lines with HTLV-I production. The mechanism of abnormal IL-2 receptor expression in HTLV infection is discussed.

Construction of chimaeric processed immunoglobulin genes containing mouse variable and human constant region sequences

The specificity of monoclonal antibodies provides a powerful diagnostic and therapeutic tool in investigating human neoplasia. Radiological scanning and immunotherapy with mouse tumour-specific monoclonal antibodies have been applied to patients with some success, but a major problem is the neutralization of the mouse antibody induced by repeated administration of heterologous antibodies. To avoid or reduce such immune reactions, chimaeric immunoglobulins consisting of mouse variable (V) and human constant (C) regions can be synthesized. We have constructed a recombinant retrovirus DNA carrying genomic heavy-chain (H) variable-diversity joining (VH-D-JH) and C gamma 1 genes from different species and show here that the chimaeric intervening sequences are spliced out precisely. This procedure provides a useful method to construct the chimaeric mouse-human immunoglobulin gene to be expressed in Escherichia coli, yeast and animal cells. Unexpectedly, a hidden splice donor site in the 5'-flanking region of a human VH gene is used in place of the donor site of the leader sequence exon, resulting in the formation of the V region without the leader sequence.

Nucleotide sequence of mouse IL-2 receptor cDNA and its comparison with the human IL-2 receptor sequence

We have cloned cDNA encoding the mouse interleukin-2 (IL-2) receptor from a murine T cell line, CTLL using human IL-2 receptor cDNA as probe. COS 7 cells transfected with the cDNA expressed the antigen recognized by the monoclonal antibody against the murine IL-2 receptor. The cDNA identified 4 species of mRNA (4.5, 3.5, 2.2 and 1.5 kb) of the mouse IL-2 receptor in CTLL cells. Difference in the length of mRNA seems to be ascribed to the variable length of the 3' untranslated sequence. Total nucleotide sequence (approximately 1400 bp) of this cDNA was determined and compared with the human receptor. The nucleotide and amino acid sequences of the IL-2 receptor are 70% and 60%, respectively, homologous in average between the two species. The comparison has revealed several conserved regions localized to particular exons such as transmembrane and cytoplasmic portions, suggesting that these regions are important for receptor function and its regulation.

TCGF (IL 2)-receptor inducing factor(s). I. Regulation of IL 2 receptor on a natural killer-like cell line (YT cells)

A continuous cell line (YT cells) with inducible receptor for T cell growth factor (TCGF)/interleukin 2 (IL 2) was established from a 15-yr-old boy with acute lymphoblastic lymphoma and thymoma. YT cells were tetraploid, having 4q+ chromosomal markers, and proliferated continuously in vitro without conditioned medium (CM) or IL 2. They were weakly positive for OKT9, OKT11, and Tac antigen (Ag), a determinant closely associated with the receptor for IL 2 (IL 2-R), and were negative for OKT1, OKT3, OKT4, and OKT8 Ag. YT cells also expressed HNK-1 Ag and Fc receptors for IgG, which are expressed on natural killer (NK) cells. They retained a killing activity against human cell lines, including K562 (myeloid), T, and B cell lines. Unlike Tac Ag/IL 2-R(+) cell lines derived from adult T cell leukemia (ATL), YT cells were negative for HTLV, as proved by Southern blotting with cDNA for viral DNA. The expression of Tac Ag was markedly enhanced in 18 hr, when YT cells were incubated with CM from PHA-stimulated peripheral blood leukocytes (PBL) or spleen cells, as determined by immunofluorescence by using flow cytometry and binding assay with 125I-anti-Tac antibody (Ab). The binding study with 125I-labeled recombinant IL 2 showed 3.2 X 10(4) IL 2 receptor sites on YT cells precultured with CM. PHA-P and Con A neither agglutinate nor enhance the expression of IL 2-R/Tac antigen on these non-T cell line cells. Furthermore, neither recombinant IL 2 nor gamma-interferon could induce IL 2-R on YT cells, suggesting the presence of a unique IL 2-R inducing factor in PBL or spleen CM. Unlike Tac Ag on HTLV(+), ATL-derived cell lines (Hut-102, MT-1, ATL-2), the expression of Tac Ag on YT cells was down-regulated by anti-Tac Ab. The induction of Tac Ag/IL 2-R on YT cells seemed specific, because the enhancement of Tac Ag expression was not associated with that of Ia Ag and T9/transferrin receptor.

TCGF (IL 2)-receptor inducing factor(s). I. Regulation of IL 2 receptor on a natural killer-like cell line (YT cells)

A continuous cell line (YT cells) with inducible receptor for T cell growth factor (TCGF)/interleukin 2 (IL 2) was established from a 15-yr-old boy with acute lymphoblastic lymphoma and thymoma. YT cells were tetraploid, having 4q+ chromosomal markers, and proliferated continuously in vitro without conditioned medium (CM) or IL 2. They were weakly positive for OKT9, OKT11, and Tac antigen (Ag), a determinant closely associated with the receptor for IL 2 (IL 2-R), and were negative for OKT1, OKT3, OKT4, and OKT8 Ag. YT cells also expressed HNK-1 Ag and Fc receptors for IgG, which are expressed on natural killer (NK) cells. They retained a killing activity against human cell lines, including K562 (myeloid), T, and B cell lines. Unlike Tac Ag/IL 2-R(+) cell lines derived from adult T cell leukemia (ATL), YT cells were negative for HTLV, as proved by Southern blotting with cDNA for viral DNA. The expression of Tac Ag was markedly enhanced in 18 hr, when YT cells were incubated with CM from PHA-stimulated peripheral blood leukocytes (PBL) or spleen cells, as determined by immunofluorescence by using flow cytometry and binding assay with 125I-anti-Tac antibody (Ab). The binding study with 125I-labeled recombinant IL 2 showed 3.2 X 10(4) IL 2 receptor sites on YT cells precultured with CM. PHA-P and Con A neither agglutinate nor enhance the expression of IL 2-R/Tac antigen on these non-T cell line cells. Furthermore, neither recombinant IL 2 nor gamma-interferon could induce IL 2-R on YT cells, suggesting the presence of a unique IL 2-R inducing factor in PBL or spleen CM. Unlike Tac Ag on HTLV(+), ATL-derived cell lines (Hut-102, MT-1, ATL-2), the expression of Tac Ag on YT cells was down-regulated by anti-Tac Ab. The induction of Tac Ag/IL 2-R on YT cells seemed specific, because the enhancement of Tac Ag expression was not associated with that of Ia Ag and T9/transferrin receptor.

Introduction of mouse C epsilon genes into Cos-7 cells and fertilized mouse eggs

A fragment of the cloned gene for the mouse C epsilon chain, coding for the first, second, third, and fourth domains, has been coupled to the SV40 promotor region (pSV2-mC epsilon). About 50 copies of pSV2-mC epsilon or its PvuII-EcoRI fragments were introduced into Cos-7 cells. Expression of PvuII-EcoRI fragments of pSV2-mC epsilon was observed in about 50% of the Cos-7 cells by indirect fluorescence staining. However, no expression of circular pSV2-mC epsilon was observed. About 200 copies of linearized pSV2-mC epsilon with EcoRI were introduced into fertilized mouse eggs. Two of 78 mice born from these eggs had integrated mouse C epsilon genes. Mouse C epsilon gene was shown to be integrated in a tandem array and as intact structures without undergoing gross deletions or rearrangements, judged from the Southern blotting patterns from several restriction enzymes. The first transgenic mouse was mated to a normal male to examine whether mouse C epsilon gene were stably transmitted to progeny. Among 5 mice to which the C epsilon gene had been transmitted, one deleted 5 copies of this gene and another deleted one junction fragment, thus demonstrating relatively unstable transmission. No C epsilon mRNA was detected in the liver, kidney, brain, lung, skeletal muscle, heart, testis, or spleen of a transgenic mouse.

Polymorphisms of a human variable heavy chain gene show linkage with constant heavy chain genes

In this study, restriction fragment length polymorphisms (RFLPs) were identified with an immunoglobulin variable heavy chain region (Ig VH) probe and the inheritance of the polymorphisms was analyzed in families. Linkage within the VHII gene cluster and between the VHII and Ig CH genes was investigated by lod (logarithm of odds) score analysis. In addition, the position of the VHII genes was determined in relation to another polymorphic locus--D14S1, which is tightly linked and centromeric to the CH genes. Genetic associations between genes in the CH and VH clusters were analyzed. These RFLPs represent genetically characterized VH region polymorphisms and it is hoped that they will facilitate the study of disease correlations as well as further the understanding of the genetics of the immunoglobulin heavy chain genes in humans.

[Bacteriological, pharmacokinetic and clinical studies on sulbactam/cefoperazone in the pediatric field]

Bacteriological and clinical effect of a newly developed SBT/CPZ in the treatment for pediatric patients was assessed by a study group consisting of 15 institutions. The results were as follows. Antibacterial effect Susceptibility studies were performed with 93 clinical isolates. The MIC of SBT/CPZ was one-tube inferior or almost similar to that of CPZ in susceptible organisms. In CPZ-resistant organisms at the inoculum of 10(8) cells/ml, however, SBT/CPZ was much superior to CPZ on the basis of the MIC. When the MIC of SBT/CPZ was compared to that of CPZ in 27 strains which have high beta-lactamase-producing activity, it was found that many of CPZ-resistant organisms were susceptible to SBT/CPZ. Serum concentration and urinary excretion The serum concentrations of SBT and CPZ were 33.2 micrograms/ml, respectively at 15 minutes after 20 mg/kg SBT/CPZ was administered by intravenous bolus injection, and those of SBT and CPZ, 51.0 micrograms/ml and 108.3 micrograms/ml, respectively following 40 mg/kg SBT/CPZ therapy. The serum concentrations of CPZ were 2.1-2.4 times as high as those of SBT. The concentrations were dose-related. The half-lives of SBT and CPZ following 20 mg/kg SBT/CPZ administration were 0.94 hour and 1.50 hours, respectively, and those following 40 mg/kg SBT/CPZ were 0.95 hour and 1.53 hours, respectively. There was no significant difference between 20 mg/kg and 40 mg/kg administrations. When compared between SBT and CPZ, CPZ had slightly longer half-lives. At the termination of 1 hour drip infusion of 20 mg/kg SBT/CPZ, the serum concentrations of SBT and CPZ were 16.7 micrograms/ml and 40.1 micrograms/ml, respectively. In the case of 40 mg/kg, the levels of SBT and CPZ were 38.6 micrograms/ml and 94.9 micrograms/ml, respectively. The concentrations were found to be dose-related as were following intravenous bolus injections. The SBT half-lives obtained after 20 mg/kg and 40 mg/kg SBT/CPZ administrations were 1.39 hours and 0.89 hour, respectively; those of CPZ, 2.00 hours and 1.44 hours, respectively. The highest urinary concentration occurred 0-2 hours after intravenous bolus injections of 20 mg/kg or 40 mg/kg SBT/CPZ. Urinary excretion of SBT over 6 hours was 60.0% and 67.7%, and that of CPZ, 21.2% and 25.0%, indicating higher urinary excretion for SBT. When 20 mg/kg SBT/CPZ or 40 mg/kg was administered over 1 hour by drip infusion, urinary excretion became the highest at 1-3 hours after administration. Urinary excretion of SBT over 7 hours following 20 mg/kg and 40 mg/kg SBT/CPZ was 68.8% and 80.3%, respectively, and that of CPZ, 24.4% and 27.3%. The results were similar to those observed following intravenous bolus injections.

Isolation of cDNA clones specifying the fourth component of mouse complement and its isotype, sex-limited protein

cDNA clones specific for the fourth component of mouse complement (C4) and its hormonally regulated isotype, sex-linked protein (Slp), were isolated using as a probe a 20-mer synthetic oligonucleotide corresponding to a known sequence of human C4 cDNA. Two types of clones, one specific for C4 (pFC4/10, with a 3.7 kilobase insert) and one specific for Slp (pFSlp/1, with a 4.7 kilobase insert), were isolated from liver cDNA libraries constructed from the Slp-producing FM mouse strain. The cDNA inserts of these clones shared 70% of the restriction sites determined. Only one type of clone was isolated from the Slp-negative DBA/1 strain; this type showed restriction maps indistinguishable from that of pFC4/10. pFC4/10 and pFSlp/1 displayed extensive homology: 94% nucleotide homology and 89% derived amino acid homology in the C4a region and 92% nucleotide homology and 89% derived amino acid homology in the thiol-ester region. An Arg-Gln-Lys-Arg sequence in the beta-alpha junction and a Cys-Ala-Glu-Gln sequence in the thiol-ester site were identified for both proteins. A remarkable divergency between C4 and Slp sequences was recognized in the region immediately following the C4a sequence.

Molecular cloning of cDNA encoding human interleukin-2 receptor

The human interleukin-2 (IL-2) receptor was purified by affinity chromatography using the anti-Tac monoclonal antibody, and its N-terminal amino acid sequence was determined. Complementary DNA clones were isolated and sequenced to reveal the primary structure of the IL-2 receptor precursor, which has 272 amino acid residues. The receptor is separated into two domains by a putative 19-residue transmembrane region. Two mRNAs (1.4 and 3.5 kilobases) hybridizing to the cDNA clone were found in human T cells bearing the IL-2 receptor. The cDNA directed synthesis of the IL-2 receptor in COS cells.

[Clinical experience on sulbactam/cefoperazone in the pediatric field]

Approximately 20 mg/kg/day of sulbactam/cefoperazone (SBT/CPZ) was given by one shot intravenous injection to 16 pediatric inpatients with respiratory tract infections (13 cases), urinary tract infection (1 case), skin infection (1 case) or gastrointestinal tract infection (1 case). An excellent efficacy in 6 cases and a good efficacy in 10 cases were observed. Causative organisms were not identified in the respiratory tract infections, even though the efficacy was excellent or good. Side effects were not noticed in particular and SBT/CPZ was judged as safe enough agent. Concentrations of SBT/CPZ in the spinal fluid were determined in 3 patients. Their low concentrations suggested the poor transfer into the spinal fluid. Finally, SBT/CPZ is a very useful agent since it is effective also against resistant organisms which produce penicillinase-type beta-lactamases.

Immunoglobulin gene organization of ultraviolet-illuminated human lymphoblastoid cell lines producing both IgM and IgG

We have studied the immunoglobulin gene organization of ultraviolet light (u.v.)-induced variant cells derived from an Epstein-Barr virus-transformed cell line. One variant produced IgG1 and two variants produced both IgM and IgG1 whereas the parental cell line produced IgM. Southern blot analyses of DNAs of these cells revealed a newly rearranged JH fragment in all the variants. The newly rearranged JH fragment also hybridized with the C gamma 1 sequence. The mu and gamma 1 chains produced in the double isotype-producing variants share the same VH sequence. u.v. illumination also induced rearrangement of the C lambda gene in the IgG1-producing variant. The double isotype producers contained the immunoglobulin gene organization and mutation best explained by fusion of the IgG1 producer and the parental IgM producer.

Concerted evolution of the mouse immunoglobulin gamma chain genes

The nucleotide sequences of the immunoglobulin heavy-chain constant region genes of mouse, C gamma 3, C gamma 1, C gamma 2b and C gamma 2a, together with that of a human equivalent C gamma 4 were compared. All the six pairs of genes within the mouse C gamma gene family contain DNA segments that exhibit marked homology, whereas no such segmental homology was found in interspecies comparisons. This result indicates that the four C gamma genes of the mouse evolved concertedly by exchanging parts of their genetic information with each other either by gene conversion or by double unequal crossing-over. Another example of such concerted evolution was found in gene regions encoding membrane domains of the mouse C gamma chains. We also searched for such segmental homologies in other mammalian C gamma gene families and found at least two more examples in man and guinea-pig. In the mouse C gamma gene family, the silent positions of an exon encoding the third domain of C gamma chains show much greater divergence in sequence than other regions, indicating that the genetic information encoded by this gene region was least scrambled during recent evolution. A phylogenetic tree constructed from the nucleotide differences of this exon demonstrates that at least two C gamma genes had already existed before mammalian radiation. Based on these results, evolution of mammalian C gamma gene families is discussed.

Isolation and characterization of endonuclease J: a sequence-specific endonuclease cleaving immunoglobulin genes

An endonuclease activity which cleaves close to the recombination sites of the immunoglobulin JK segments was found in extracts of chicken bursa of Fabricius and characterized after partial purification. The enzyme preparation also cleaved a VK segment at its 3' end. A similar activity was found in mouse liver, mouse myelomas and Hela cells. The enzyme designated as endonuclease J introduces double-stranded cleavages preferentially at sequences containing G clusters of pBR322 as well as the JK segments. However, not all the G clusters were cleaved by endonuclease J, suggesting that the enzyme recognizes additional sequences. Deletion of the conserved nonamer (GGTTTTTGT) located immediately 5' to the JK4 segment drastically reduced the cleavage activity of its immediate downstream G cluster. Although biological function of endonuclease J is not clear at this stage, the possibilities of its involvement in the immunoglobulin gene recombination and general recombination were discussed.

Rearranged immunoglobulin heavy chain variable region (VH) pseudogene that deletes the second complementarity-determining region

We have cloned two rearranged heavy chain variable region (VH) genes from the IgG-producing human cell line CESS. The VH gene, which is linked to the mu chain constant region (C mu) gene, has two deletions at residues 45-62 and 82A-90, the former of which corresponds closely to the second complementarity-determining region (CDR2). These results could indicate that translocation of CDR2 occurred and could give support to the argument that reassortment of the V mini-genes is involved in the generation of hypervariability during evolution. However, the rearranged pseudogene could have also arisen by fortuitous deletion. The other VH gene of CESS is an expressed form and is probably linked to the C gamma gene. The diversity region (D) segments used in these rearranged V genes are less than 38% homologous to known human germline D segments, indicating the presence of more unknown germline D segments.

Introduction of human gamma 1 immunoglobulin genes into fertilized mouse eggs

A rearranged human gamma 1 immunoglobulin gene was introduced into fertilized mouse eggs. The phage Ch4A-VCE-gamma 1 was constructed by ligating an EcoRI and BglII fragment of pBR322-CESSV(CE-1) containing the VDJ region with an EcoRI and BamHI fragment of Ch4A-HIg gamma 1-10 containing the gamma 1 constant region. About 200 copies of Ch4A-VCE-gamma 1 genes were introduced into fertilized mouse eggs. Of 489 eggs injected with these genes, 319 survived and were transferred to oviducts of foster mothers. Thirtyeight mice were born and were screened for the presence of human gamma 1 immunoglobulin genes by Southern blot hybridization. Five of these 38 mice had integrated human gamma 1 immunoglobulin genes. None of the human gamma 1 copies in each mouse had undergone deletions or rearrangements as judged by the Southern blotting patterns for several restriction enzymes. Human gamma 1 gene was present in several different tissues. All the mice tested so far transmit the human gamma 1 gene to a fraction of their offspring in an autosomal dominant manner. Spleen cells from transgenic mice were analyzed for immunoglobulin production by reverse plaque assay or immunofluorescence staining of cytoplasmic immunoglobulin, but synthesis and secretion of human gamma 1 chains could not be detected. No human gamma 1 immunoglobulin mRNA was detected in the liver and spleen of a transgenic mouse. The presence of the human gamma 1 immunoglobulin gene appeared to have no effect on the expression of endogenous mouse immunoglobulin genes.

Genomic structure of HTLV (human T-cell leukemia virus): detection of defective genome and its amplification in MT-2 cells

We studied the genomic structure of human T-cell leukemia virus (HTLV) in the HTLV producer cell line MT-2. Southern blotting revealed that at least eight HTLV proviruses were integrated in the chromosomes of MT-2 cells. The genomic structure of these proviruses was analyzed using fragments of cloned HTLV that were specific to gag, pol, env, pXs and U3R genes as probes. We have identified a complete genome of HTLV in MT-2 (non-defective type). However, seven of the eight proviruses had defective genomes. Provirus T2-a contains only the U3R (LTR) of HTLV and T2-b corresponds to the non-defective genome. T2-c possesses only a portion of env, and pXs and U3R. T2-d consists of gag, pol, part of env and U3R. On the other hand, T2-e, f, g and h consist of gag, pXs and U3R. Northern blotting experiments with mRNA from MT-2 cells supported the evidence of amplification of the gag-pXs gene of HTLV. 26S mRNA is considered to be a subgenomic species of 35S RNA. 32S mRNA may represent the T2-d provirus which lacks a portion of env and pXs, while 20S mRNA was a subgenomic species. The gag-pXs gene may correspond to 24S mRNA, the amount which was amplified in MT-2 cells.