Alkyl Hydrogen Phosphonate Derivatives of the anti-HIV Agent AZT may be Less Toxic than the Parent Nucleoside Analogue

Novel alkyl hydrogen phosphonate derivatives of the anti-HIV nucleoside analogue AZT have been prepared by phosphorochloridite chemistry. These materials are designed to act as labile membrane-soluble prodrugs of the bioactive free nucleotides. In vitro evaluation has revealed the compounds to have a pronounced and selective antiviral action. Short-chain (C1-C7) alkyl derivatives are more potent than the parent hydrogen phosphonate, whilst one long-chain (C18) compound is less active. In an assay that demonstrates the toxicity of the parent drug AZT, the alkyl H-phosphonates appear to be less cytotoxic, whilst retaining full antiviral activity. Lastly, the compounds are all poorly active in a cell line (JM) that is poorly responsive to AZT, indicating that they act as depot forms of the nucleoside rather than of the free nucleotide.

Screening of Compounds for Activity against HIV: A Collaborative Study

The collaborative study was undertaken to examine the sensitivity of a range of tests used in assessing the antiviral activities of compounds against human immunodeficiency virus (HIV). A panel of 20 compounds with diverse antiviral activities against HIV were tested under code at three antiviral testing centres supported by the Medical Research Council's AIDS Directed Programme and at the European Community Centralised Facility (ECCF) for New Antiviral Compounds against AIDS in Belgium. Compounds known to have major anti-HIV activity ranked high in all assays, with the exception of the glucosidase inhibitors and certain nucleoside analogues. Results of two assays based on MT4 cells (centre IV) showed a high degree of similarity, despite the use of distinct HIV-1 (HTLV-IIIB) and HIV-2 (ROD) viruses. Considerable similarity was also observed between the assays based on HTLV-IIIRF in C8166 cells (centres I and II). Other assays performed at centre II and at centre III had enhanced sensitivity for glycosidase inhibitors. The differences in anti-HIV activity that were observed may be attributable to specific properties of the cell lines used and particular testing methodologies. The use of more than one type of assay is advisable in order not to miss compounds with low to moderate activity against HIV.

Molecular characterization of human monoclonal antibodies derived from fusions of tonsil lymphocytes with a human myeloma cell line

Recently a new human myeloma cell line (Karpas 707H) has been developed for the efficient generation of stable human hybridomas. Here we describe the first molecular characterization of human monoclonal antibodies (MAbs) produced by a human counterpart to mouse myeloma cells. We studied 30 of the hybridomas generated by fusions to tonsil lymphocytes by DNA sequencing of rearranged V-genes, and have analyzed germ-line diversity, somatic hypermutation, and heavy- and light-chain pairings. Our results suggest that the hybridoma-derived antibodies are representative of antibodies from populations of human lymphocytes and at different stages in the maturation of the response; the use of Karpas 707H myeloma for human hybridoma fusions may therefore provide a valuable tool for analysis of the human antibody responses.

Longitudinal study of serum neutralization of HIV-1 in infected plasma donors

Earlier studies provided suggestive evidence about the effectiveness of passive immunotherapy for AIDS patients using plasma donated by healthy HIV-1 infected individuals and revealed beneficial effects of plasmapheresis for the immune system of the donors. In this study, anti-HIV-1 neutralizing activity in 31 healthy HIV-1 infected donors of plasma participating in a passive immunotherapy study was investigated as a function of time. Average studied period was 33 months. Using the highly cytopathic HIV-1 NDK strain and MOLT4 cells, it was shown by means of syncytia formation inhibition assay and polyclonal HIV-1 antigen-capture assay that viral neutralizing titers tend either to remain unchanged or increase over time. These findings support the notion that the immune system is not affected adversely in HIV-1 infected plasma donors and lend further support to the feasibility of passive immunotherapy for AIDS patients.

A human myeloma cell line suitable for the generation of human monoclonal antibodies

Ever since monoclonal antibodies were produced in 1975 with mouse myeloma cells there has been interest in developing human myeloma cultures for the production of monoclonal antibodies. However, despite multiple attempts, no human myeloma line suitable for hybridoma production has been described. Here we report the derivation of a hypoxanthine-aminopterin-thymidine-sensitive and ouabain-resistant human myeloma cell line (Karpas 707H) that contains unique genetic markers. We show that this line is useful for the generation of stable human hybridomas. It can easily be fused with ouabain-sensitive Epstein-Barr virus-transformed cells as well as with fresh tonsil and blood lymphocytes, giving rise to stable hybrids that continuously secrete very large quantities of human immunoglobulins. The derived hybrids do not lose immunoglobulin secretion over many months of continuous growth. The availability of this cell line should enable the in vitro immortalization of human antibody-producing B cells that are formed in vivo. The monoclonal antibodies produced may have advantages in immunotherapy.

Safety and immunogenicity of Vi conjugate vaccines for typhoid fever in adults, teenagers, and 2- to 4-year-old children in Vietnam

The capsular polysaccharide of Salmonella typhi, Vi, is an essential virulence factor and a protective vaccine for people older than 5 years. The safety and immunogenicity of two investigational Vi conjugate vaccines were evaluated in adults, 5- to 14-year-old children, and 2- to 4-year-old children in Vietnam. The conjugates were prepared with Pseudomonas aeruginosa recombinant exoprotein A (rEPA) as the carrier, using either N-succinimidyl-3-(2-pyridyldithio)-propionate (SPDP; Vi-rEPA(1)) or adipic acid dihydrazide (ADH; Vi-rEPA(2)) as linkers. None of the recipients experienced a temperature of >38.5 degrees C or significant local reactions. One injection of Vi-rEPA(2) into adults elicited a geometric mean (GM) increase in anti-Vi immunoglobulin G (IgG) from 9.62 enzyme-linked immunosorbent assay units/ml (EU) to 465 EU at 6 weeks; this level fell to 119 EU after 26 weeks. In the 5- to 14-year-old children, anti-Vi IgG levels at 6 weeks elicited by Vi-rEPA(2), Vi-rEPA(1), and Vi were 169, 22.8, and 18.9 EU, respectively (P = 0.0001 for Vi-rEPA(1) and Vi with respect to Vi-rEPA(2)). At 26 weeks, the anti-Vi IgG levels for recipients of Vi-rEPA(2), Vi-rEPA(1), and Vi were 30.0, 10.8, and 13.4 EU, respectively (P < 0.001 for Vi-rEPA(1) and Vi with respect to Vi-rEPA(2)); all were higher than the preinjection levels (P = 0. 0001). Vi-rEPA(2) also elicited the highest anti-Vi IgM and IgA levels of the three vaccines. In the 2- to 4-year-old children at 6 weeks following the first injection, Vi-rEPA(2) elicited an anti-Vi IgG level of 69.9 EU compared to 28.9 EU for Vi-rEPA(1) (P = 0.0001). Reinjection increased Vi antibody levels from 69.9 to 95.4 EU for Vi-rEPA(2) and from 28.9 to 83.0 EU for Vi-rEPA(1). At 26 weeks, anti-Vi IgG levels remained higher than those at preinjection (30.6 versus 0.18 for Vi-rEPA(2) and 12.8 versus 0.33 for Vi-rEPA(1); P = 0.0001 for both). Vi vaccine is recommended for individuals of 5 years of age or older. In the present study, the GM level of anti-Vi IgG elicited by two injections of Vi-rEPA(2) in the 2- to 4-year-old children was higher than that elicited by Vi in the 5- to 14-year-old children (30.6 versus 13.4; P = 0.0001). The safety and immunogenicity of the Vi-rEPA(2) conjugate warrant further investigation.

Delineation of the breakpoint at 18q21.1 in a cell line (Karpas1106) derived from mediastinal B-cell lymphoma by fluorescence in situ hybridization with multiple YAC clones

The breakpoint of the 18q21 translocation of B-cell-non-Hodgkin's lymphoma (NHL) cell line Karpas1106P was delineated by fluorescence in situ hybridization (FISH). Karpas1106P was derived from mediastinal lymphoblastic B-cell lymphoma and exhibited the immunophenotype characteristic of marginal-zone B-cell lymphoma (MZL): smIg+, pan-B antigen+, CD5-, CD10- and CD23-. The original G-banded karyotype showed a complex translocation containing t(X;18;13)(q28;q21;q12.1). Double-color FISH (DCFISH) with whole-chromosome-painting (WCP) probes for chromosomes X, 13 and 18, and 18q-specific yeast artificial chromosome (YAC) clones defined t(X;18;13) as ider(X)t(X;18; 13)(q28;q 12.3q21.1;q12.1). The immunoglobulin-heavy-chain (IgH) gene was not involved in the chromosomal translocation as detected by DCFISH with VH and Cgamma probes. By using contiguous YAC clones mapped from 18q12.3 to q21.1, we identified a YAC clone y852H2 with its breakpoint at 18q21.1. In Karpas1106P, the distal part of chromosome 18 from the breakpoint (18q21.1-qter) was deleted, showing loss of heterozygosity of this region. In addition, the chromosomal segment 18q21.1 was duplicated and inserted to ider(X)t(X;18; 13) between Xq28 and 13q12.1 with maintaining its original orientation. The DNA sequence of the breakpoint region contained in y852H2 can serve as a candidate locus for further molecular dissection to identify the causative gene of MZL.

Passive immunotherapy in advanced HIV infection and therapeutic plasmapheresis in asymptomatic HIV-positive individuals: a four-year clinical experience

We have been treating patients with advanced HIV disease using passive immunotherapy (PIT). Earlier studies of PIT which have been published concerned relatively short periods of treatment: our study is by far the longest and reports also on the long-term effects of plasmapheresis on healthy HIV-infected individuals. Fifty-nine patients with an average CD4+ T-cell count of 55 per cu.mm. at baseline were transfused at monthly intervals with 500 ml of hyperimmune plasma. No disease progression or death occurred among the 8 asymptomatic patients under the treatment, which lasted for 36.25 months on average. Seven of the 15 ARC patients progressed to AIDS but none died in an average period of 25.9 months. Seven of the 36 symptomatic AIDS patients with advanced disease died in an average period of 19.6 months. PIT appears to be nontoxic and to have beneficial effects lasting at least four years under continuous treatment. It probably delays disease progression in ARC and AIDS patients, and almost certainly does so in asymptomatic late HIV infection with a very low CD4+ T-cell count. None of the 51 donors suffered adverse effects, nor did any progress to ARC or AIDS in an average period of 30.1 months. Their laboratory parameters indicated a nearly stable condition: in particular, their average CD4+ T-cell count rose from 478 to 498. The study of our plasma donors indicated that repeated and frequent plasma donation by asymptomatic HIV-infected individuals could delay disease progression, although further studies are needed to investigate this.

How to prolong the effects of combination therapy for HIV

Infection with HIV leads to AIDS and death in about 90% of patients within ten years. The first generation of anti-HIV drugs inhibited the viral enzyme reverse transcriptase (RT); but long-term studies have revealed side-effects and a high rate of emergence of drug-resistant HIV mutants. The more recent combination of two anti-RT drugs and a protease inhibitor appears to be more promising: approximately 75% of AIDS patients benefit. However, increasing numbers of treatment failures from toxicity and drug-resistant mutants are emerging. Passive immunotherapy (PIT) is a non-toxic form of treatment based on the neutralization of HIV with antibody-rich plasma from healthy HIV-positive individuals. Studies show it can benefit AIDS patients. Here, we suggest that, in combination with anti-HIV drugs, PIT could reduce some of the toxicity of the latter and limit the emergence of drug-resistant HIV strains. In addition, regular plasma donation seems to be beneficial to the donors.

On the antigenic determinants of the lipopolysaccharides of Vibrio cholerae O:1, serotypes Ogawa and Inaba

Monoclonal, murine IgG1s S-20-4, A-20-6, and IgA 2D6, directed against Vibrio cholerae O:1 Ogawa-lipopolysaccharide exhibited the same fine specificities and similar affinities for the synthetic methyl alpha-glycosides of the (oligo)saccharide fragments mimicking the Ogawa O-polysaccharide (O-PS). They did not react with the corresponding synthetic fragments of Inaba O-PS. IgG1s S-20-4 and A-20-6 have absolute affinity constants for synthetic Ogawa mono- to hexasaccharides of from approximately 10(5) to approximately 10(6) M-1. For IgG1s S-20-4, A-20-6, and IgA 2D6, the nonreducing terminal residue of Ogawa O-PS is the dominant determinant, accounting for approximately 90% of the maximal binding energy shown by these antibodies. Binding studies of derivatives of the Ogawa monosaccharide and IgGs S-20-4 and A-20-6 revealed that the C-2 O-methyl group fits into a somewhat flexible antibody cavity and that hydrogen bonds involving the oxygen and, respectively, the OH at the 2- and 3-position of the sugar moiety as well as the 2'-position in the amide side chain are required. Monoclonal IgA ZAC-3 and IgG3 I-24-2 are specific for V. cholerae O:1 serotypes Ogawa/Inaba-LPS.1 The former did not show binding with members of either series of the synthetic ligands related to the O-antigens of the Ogawa or Inaba serotypes, in agreement with its reported specificity for the lipid/core region (1). Inhibition studies revealed that the binding of purified IgG3 I-24-2 to Ogawa-LPS might be mediated by a region in the junction of the OPS to the lipid-core region of the LPS. cDNA cloning and analysis of the anti-Ogawa antibodies S-20-4, A-20-6, and 2D6 revealed a very high degree of homology among the heavy chains. Among the light chains, no such homology between S-20-4 and A-20-6 on the one hand, and 2D6 on the other hand, exists. For the anti-Inaba/Ogawa antibodies I-24-2 and ZAC-3, their heavy chains are completely different, with some homology among the light chains.

Can repeated plasma donation by asymptomatic HIV-infected individuals delay the onset of AIDS?

Healthy HIV-positive regular donors of plasma in a programme of passive immunotherapy for AIDS patients were studied over a period of about two years. None developed symptoms of clinical progression; most seemed to make substantial gains of CD4 cells by comparison with asymptomatic individuals who were not donating. The effects of donation did not seem to diminish with repetition, and donor CD4 counts tended towards stabilizing within normal limits. Asymptomatic HIV-positive individuals were compared immunologically with 'normals' and people with AIDS, using a battery of 25 measurements on peripheral blood. The immunological profiles of donor and non-donor asymptomatics, indistinguishable at the start, became dissimilar: donors' profiles resembled AIDS less, non-donors became less like 'normal' and a few non-donor results could not be distinguished from AIDS. Improvement in the CD4 counts and amelioration of the immunological profile in donors provide prima facie evidence that plasmapheresis may be therapeutic for asymptomatic HIV-positive people. Further studies are justified.

Enzyme immunoassays using bispecific diabodies

BACKGROUND

Bispecific antibodies with a first binding specificity to a target antigen and a second to an enzyme have great potential in enzyme immunoassays. As bispecific antibodies are difficult to make, the use of recombinant bispecific antibody fragments may provide a breakthrough.

OBJECTIVES

To make bispecific antibody fragments directed against an enzyme and to demonstrate their application in enzyme immunoassays.

STUDY DESIGN

Bispecific antibody fragments were assembled as diabodies (Holliger P., Prospero T., Winter G. Proc. Natl. Acad. Sci. USA 90, 1993, 6444-6448) directed to an enzyme, E. coli beta-galactosidase, and to each of three target antigens, hen-egg lysozyme (HEL), carcinoembryonic antigen (CEA), and HIV gpl20 (HIV). The diabodies were then evaluated in immunoassays.

RESULTS

The HEL diabody was shown to recruit beta-galactosidase in a microtiter plate immunoassay in which diabody and enzyme were co-incubated with antigen, washed and enzyme substrate added. The CEA diabody was shown to detect CEA by immunocytochemical staining of transfected, CEA-expressing HeLa cells and of adenocarcinoma colon tissue sections, and the HIV diabody to detect gpl20 in immunoblots of total cell extracts.

CONCLUSION

The results illustrate the diagnostic potential of diabodies in enzyme immunoassays.

Comparison of concentrations of Cry j 1 and Cry j 2 in diploid and triploid Japanese cedar (Cryptomeria japonica) pollen extracts

Japanese cedar (Cryptomeria japonica) possibilities has been a serious allergic disease in Japan. There are two kinds of Japanese cedar trees; the popular one is diploid, the less popular is triploid. These trees are not very different morphologically. However, the relative allergenicity of their pollens is unknown, although both major allergens, Cry j 1 and Cry j 22, have been purified and cloned from the diploid line. Triploid trees are sterile and the allergenicity of their pollen may differ. Using Japanese-cedar-allergic patient sera, we compared the concentration of these two major allergens in both kinds of pollen. Pollen collected from different years and regions was also studied. The results indicate that triploid tree pollen extract has lower concentrations of both major allergens; therefore, the pollen may be less allergenic.

Production, binding characteristics and protective immunity of monoclonal antibody to pneumococcal type-9V conjugate

A monoclonal antibody (MAb) to pneumococcal type-9V polysaccharide (PS) was produced using PS conjugated to inactivated pneumolysin as the immunogen. The MAb to 9V PS was of the IgG1 subclass. The antigen-antibody reaction increased rapidly at low concentrations and reached a plateau at 10 micrograms PS/ml as measured by nephelometry of the group 9 PS against 9V MAb binding. In contrast, the binding of group 9 PS against rabbit 9V antiserum (AS) increased proportionally and continued to increase up to the highest concentration of PS tested (20 micrograms PS/ml). The 9V MAb reacted with all group 9 PSs (9A, 9L, 9N and 9V) by immunodiffusion. In the homologous 9V Ag-MAb reaction, there were marked differences in the inhibition of binding by the cross-reactive 9L PS (19.2% inhibition) and the 9N PS (0.2%). In contrast, inhibition of the homologous 9V Ag-rabbit AS binding by cross-reactive 9L and 9N PSs ranged from 57.8 to 62.7%. Removal of the O-acetyl group from 9V PS by alkali hydrolysis resulted in decreased binding with rabbit 9V AS. However, the binding reaction with 9V MAb was less affected by the loss of O-acetyl content. The 9V MAb was both opsonic and passively protected young mice against challenge with type-9V pneumococci.

Of four murine, anti-Shigella dysenteriae type 1 O-polysaccharide antibodies, three employ V-genes that differ extensively from those of the fourth

Three murine, monoclonal antibodies, IgM 5286 F2, IgM 5297 C1, and IgG 5338 H4 were generated against Shigella dysenteriae type 1 O-specific polysaccharide (O-SP)-conjugate. They are specific for the O-SP, which is a poly-[alpha-L-rhamnopyranosyl-(1-->3)-alpha-L-rhamnopyranosyl-(1-->2)-al pha-D-galactopyranosyl-(1-->3)-2-deoxy-2-amino-N-acetyl-alpha-D-glucopyr anosyl]. The VH and VL genes of these antibodies were cloned and their sequences determined. They showed 93% homology, but were quite different to the primary sequence of IgM 3707 E9, of the same O-SP-specificity, previously reported. The fine-specificities of both IgG 5338 H4 and IgM 3707 E9 were for the same disaccharide moiety in the O-SP, while IgMs 5286 F2 and 5297 C1 showed fine-specificity for the entire repeating unit of the O-SP. Therefore, divergent sequences can confer upon antibodies similar-, or even identical-carbohydrate-epitope fine-specificity. In addition, close primary sequence-homology does not preclude differences in antibody fine-specificity.

Characterization of a novel murine leukemia virus-related subgroup within mammals

The murine leukemia virus (MuLV)-related retroviruses are one of seven genera which together constitute the family Retroviridae. They are widespread as both endogenous and exogenous agents within vertebrates and have been associated with a variety of malignancies and other disorders. We isolated and characterized 12 endogenous representatives of this genus from a number of mammalian hosts. Subsequent sequence analysis revealed that the isolated viruses cluster into two clearly distinct groups. All of the exogenous MuLV-related retroviruses which have been isolated to date, as well as several endogenous examples, fall into the first group, whereas the second group is represented solely by endogenous representatives, including human endogenous retrovirus type E (HERV.E). The two groups are widespread within mammals, with both often present within one animal species. Despite this, there is no evidence to date that recombination between members of the different groups has occurred. Genetic distances and several other properties of the HERV.E genome suggest that if exogenous members of this subgroup exist, they are likely to have biological properties different from those of the other exogenous viruses of this genus. Several of these viruses are known to have been integrated within their hosts' genomes for a long period of time, and a most recent divergence date for the MuLV and HERV.E subgroups can thus be proposed. This date, approximately 30 million years ago, is the most recent date possible, and it is probable that the actual period of time since their divergence is significantly longer.

Antigenic topology of the P29 surface lipoprotein of Mycoplasma fermentans: differential display of epitopes results in high-frequency phase variation

Antibodies to P29, a major lipid-modified surface protein of Mycoplasma fermentans, reveal phase variation of surface epitopes occurring with high frequency in clonal lineages of the organism. This occurs despite continuous expression of the entire epitope-bearing P29 product (detected by Western immunoblotting) and contrasts with phase variation of other surface antigens mediated by differential expression of proteins. To understand the structure and antigenic topology of P29, the single-copy p29 gene from strain PG18 was cloned and sequenced. The gene encodes a prolipoprotein containing a signal sequence predicted to be modified with lipid and cleaved at the N-terminal Cys-1 residue of the mature P29 lipoprotein. The remaining 218-residue hydrophilic sequence of P29 is predicted to be located external to the single plasma membrane. Additional Cys residues at positions 91 and 128 in the mature protein were shown to form a 36-residue disulfide loop by selectively labeling sulfhydryl groups that were liberated only after chemical reduction of monomeric P29. Two nearly identical charged amino acid sequences occurred in P29, within the disulfide loop and upstream of this structure. Two distinct epitopes binding different monoclonal antibodies were associated with opposite ends of the P29 protein, by mapping products expressed in Escherichia coli from PCR-generated 3' deletion mutations of the p29 gene. Each monoclonal antibody detected high-frequency and noncoordinate changes in accessibility of the corresponding epitopes in colony immunoblots of clonal variants, yet sequencing of the p29 gene from these variants and analysis of disulfide bonds revealed no associated changes in the primary sequence or disulfide loop structure of P29. These results suggest that P29 surface epitope variation may involve masking of selected regions of P29, possibly by other surface components undergoing phase variation by differential expression. Differential masking may be an important mechanism for altering the antigenic or functional surface topology of this mycoplasma and other wall-less mycoplasmas.

Easel, a gypsy LTR-retrotransposon in the Salmonidae

Despite the close similarities between retroviruses and the gypsy/Ty3 group of LTR-retrotransposons their host ranges are largely distinct: the retroviruses are found only in vertebrates, whereas the gypsy LTR-retrotransposons are almost exclusively restricted to invertebrates, plants and fungi. Here we report the amplification by PCR, and characterisation, of one of the first LTR-retrotransposons to be discovered in vertebrates--in several members of the piscine family Salmonidae. Phylogenetic analysis of this retroelement, termed easel, indicates that it is probably a phylogeneticaly basal member of the gypsy group of LTR-retrotransposons and occurs in some of the same species from which retroviruses have previously been isolated. Thus some members of the Salmonidae are the first organisms known to harbour both retroviral branch elements and the gypsy LTR-retrotransposon branch elements. This creates an overlap in the host ranges of the two retroelement families.

A murine antibody to Shigella dysenteriae type 1 employs V-genes that contain a rearranged codon for the lambda light chain

The cDNA coding for a hybridoma anti Shigella dysenteriae type 1 antibody (3707 E9) has been cloned, and sequenced. Binding patterns with fragments of the bacterial polysaccharide antigen had already been studied in detail. The VH sequence utilizes the VH441 gene, first identified amongst beta-(1,6)galactan-binding antibodies, while the VL is closely related to the V lambda 1 gene. We found that the VL3707 E9 gene employed a VL-J combinatorial joining leading to a rare Trp-->Leu substitution at position L96.

Epitope specificity of the major peanut allergen, Ara h II

The antigenic and allergenic structure of Ara h II, a major allergen of peanuts, was investigated with the use of four monoclonal antibodies obtained from BALB/c mice immunized with purified Ara h II. Our previous studies with monoclonal antibodies generated to peanut allergens showed this method to be useful for epitope mapping. When used as a solid phase in an ELISA, these monoclonal antibodies captured peanut antigen, which bound human IgE from patients with positive peanut challenge responses. The Ara h II monoclonal antibodies were found to be specific for peanut antigens when binding for other legumes was examined. In ELISA inhibition studies with the monoclonal antibodies, we identified two different antigenic sites on Ara h II. In similar studies with pooled human IgE serum from patients with positive challenge responses to peanuts, we identified two closely related IgE-binding epitopes. These characterized monoclonal antibodies to Ara h II will be useful for future studies to immunoaffinity purify the Ara h II allergen and to use in conjunction with recombinant technology for determining structure-function relationships.

Binding of the O-antigen of Shigella dysenteriae type 1 and 26 related synthetic fragments to a monoclonal IgM antibody

Shigella dysenteriae type 1 possesses an O-antigen whose repeating unit is -->3)-alpha-L-Rhap-(1-->3)-alpha-L-Rhap-(1-->2)-alpha-D-Galp -(1-->3)-alpha-D- GlcpNAc-(1-->, where Rhap is rhamnopyranosyl, Galp is galactopyranosyl, and Glcp is glucopyranosyl. Using ligand-induced protein fluorescence change, we have measured the affinities of a monoclonal murine IgM for 26 fragments of, or related to, the structure of the O-polysaccharide and of the IgM Fab for the intact O-specific bacterial polysaccharide. Synthetic saccharides used were methyl glycosides to ensure an anomerically defined pyranosyl ring conformation. The galactosyl residue is the only monosaccharide of the antigenic epitope that shows quantifiable binding: approximately 3.0 kcal/mol of binding free energy, depending on the structure and conformation of the fragment it is a part of. Addition of an alpha-(1-->2)-linked rhamnosyl residue increases the free energy of binding significantly. We propose this rhamnopyranosyl-alpha-(1-->2)-galactopyranosyl disaccharide to be the basic determinant of the Shigella O-polysaccharide. Further extension (by linkages as in the natural antigen) of this oligosaccharidic ligand toward the upstream end (in an oligo- (or poly-)saccharide, such as A-->B-->C-->D-->E-->m, where A, B, C, D, and E are sugars and m is any moiety, such as methyl, we define A as the glycosyl- or upstream terminus, and E as the glycoside- or downstream terminus) by rhamnosyl and N-acetylglucosaminyl moieties improves the binding only minimally. The antibody is quite specific for the rhamnosyl-alpha-(1-->2)-galactosyl sequence but less so for the nature of the attachment to the galactosyl residue on the downstream side. Measurements using IgM Fab and the intact O-specific polysaccharide show that the antibody can bind internal segments on the antigen chain. The free energy of binding of this antibody for the disaccharide determinant varies from -delta G of 4.7 to 5.1 kcal/mol, depending on its flanking residues.

Acute leukemias of different lineages have similar MLL gene fusions encoding related chimeric proteins resulting from chromosomal translocation

The MLL gene, on human chromosome 11q23, undergoes chromosomal translocation in acute leukemias, resulting in gene fusion with AF4 (chromosome 4) and ENL (chromosome 19). We report here translocation of MLL with nine different chromosomes and two paracentric chromosome 11 deletions in early B cell, B- or T-cell lineage, or nonlymphocytic acute leukemias. The mRNA translocation junction from 22 t(4;11) patients, including six adult leukemias, and nine t(11;19) tumors reveals a remarkable conservation of breakpoints within MLL, AF4, or ENL genes, irrespective of tumor phenotype. Typically, the breakpoints are upstream of the zinc-finger region of MLL, and deletion of this region can accompany translocation, supporting the der(11) chromosome as the important component in leukemogenesis. Partial sequence of a fusion between MLL and the AFX1 gene from chromosome X shows the latter to be rich in Ser/Pro codons, like the ENL mRNA. These data suggest that the heterogeneous 11q23 abnormalities might cause attachment of Ser/Pro-rich segments to the NH2 terminus of MLL, lacking the zinc-finger region, and that translocations occur in early hematopoietic cells, before commitment to distinct lineages.

C-MYC translocations in de novo B-cell lineage acute leukemias with t(14;18)(cell lines Karpas 231 and 353)

Rare de novo acute leukemias of mature B cells may exhibit the chromosomal translocation t(14;18)(q32.3; q21.3). We report the preliminary characterization of two cases that exhibited not only t(14;18)(q32.3;q21.3) but also the novel translocation t(8;9)(q24.1;p13.3), involving the C-MYC locus with unknown sequences at 9p13.3. From these cases, two Epstein-Barr virus negative cell lines (Karpas 231 and 353) with features identical to those seen in fresh cells from the patient have been derived. Both cell lines have complex karyotypes: in addition to both t(14;18)(q32.3;q21.3) and t(8;9)(q24.1;p13.3), cell line Karpas 231 exhibited three-way translocation t(1;3;11) (q42.3;q27.1;q23.1), whereas Karpas 353 exhibited t(1;3;7)(p32.1;q21.1;q22.1). Both cases retained immunophenotypes characteristic of mature B cells with no evidence for commitment to other hematopoietic lineages. Both cases expressed abundant, normal-sized C-MYC transcript, but no rearrangement of C-MYC DNA sequences could be detected using probes that span 80 kb around the C-MYC coding sequences. Breakpoints within the BCL-2 gene were divergent. In Karpas 353 the BCL-2 breakpoint occurred within the 3' untranslated major breakpoint region (mbr) of the gene, whereas, in Karpas 231, breaks in both the 3' mbr and in the region 5' of the gene were detected. The cytogenetic combination of t(14;18)(q32.3;q21.3) and t(8;9)(q24.1;p13.3) has been previously reported in diffuse B cell lymphomas. This combination may be a new recurrent abnormality, of central pathogenic importance in the transformation of B cells to high grade malignancies through simultaneous deregulation of BCL-2 and C-MYC genes, constitutive expression of C-MYC being driven by currently unknown DNA sequences on chromosome 9p13.3. The presence of other complex translocations including those affecting 11q23.1 may further accelerate the process of acute transformation.

A new human T-cell lymphoma cell line (Karpas 384) of the T-cell receptor gamma/delta lineage with translocation t(7:14) (p13;q11.2)

A new human T-cell non-Hodgkin lymphoma cell line of the T-cell receptor (TCR) gamma/delta lineage has been derived from the peripheral blood of a patient with a subcutaneous T-cell lymphoma in leukemic phase. The cell line (Karpas 384) initially had the same characteristics as malignant cells from the patient. Both the original tumor and the cell line failed to express any T-cell differentiation antigens other than very weak cell-surface expression of CD3 and cytoplasmic CD7; with continued growth in vitro, surface CD3 became undetectable in the presence of maintained strong cytoplasmic expression. The cell line has a complex karyotype with six abnormal chromosomes exhibiting not only t(7;14) (p13;q11.2) but also inv7(p13;q22.1), t(1;2)(q11;q35), t(2;1;14) (q35;q11-q32.1;q22.1), interstitial deletion 12(q24.1q24.3), and an unidentified marker chromosome. DNA blot analysis showed that TCR C beta and TCR J alpha-C alpha DNA sequences were in germline configuration in all restriction endonuclease digests. TCR gamma sequences showed biallelic V gamma 9-J gamma P-C gamma 1 rearrangements, the TCR gamma rearrangement detected in the majority of normal TCR gamma/delta bearing cells. Use of a range of TCR delta probes showed biallelic deletion of both J delta 1 and J delta 2, but three rearranged fragments when probed with a 3' C delta genomic probe. Similar breakpoints at 7p13 have been reported in a wide range of hematologic malignancies. Molecular cloning of the t(7;14)(p13;q11.2) translocation breakpoint in this cell line may define new DNA sequences of oncogenic potential at the 7p13 locus.

The peanut-agglutinin (PNA)-binding surface components of malignant plasma cells

Plasma cells within bone marrow aspirates from multiple myeloma patients have been shown to be reactive with the lectin peanut agglutinin (PNA). This has been recently exploited by using PNA for purging bone marrow of malignant cells in autotransplantation therapy of the disease. The purpose of this investigation was to isolate and characterize the PNA-binding proteins of myeloma cells. We used the malignant plasma cell-derived line Karpas-620 (K620) as a model, and showed by affinity chromatography, SDS-PAGE, and immunoprecipitation that, among several PNA-binding proteins, a major one is an incompletely sialylated form of CD44. CD44 is a well-known homing receptor protein which is rich in carbohydrate and usually completely sialylated so that it does not react with PNA. We have then examined the PNA reactivity of myeloma cells from different patients and showed a clear difference in the profile of PNA-binding proteins from case to case. Moreover, in contrast to K620 cells, some of the patient plasma cells tested did not have a PNA-binding form of CD44. In conclusion, therefore, we have shown that a number of different proteins participate in PNA binding by malignant plasma cells. Moreover, we have demonstrated a novel, incompletely sialylated form of CD44 on a myeloma cell line. It is known that the level of glycosylation of CD44 and other proteins may affect their function, but how this relates to the malignant behaviour of plasma cells remains to be determined.

Prevalence of human immunodeficiency virus (HIV) antibody among apparently healthy pregnant women in Nigeria

OBJECTIVE

To determine the prevalence of human immunodeficiency virus (HIV) in pregnancy in our community.

METHOD

A prospective study on 250 pregnant women currently attending the antenatal clinic at the Lagos University Teaching Hospital was carried out in 1991.

RESULT

Results obtained showed that of the 250 pregnant women screened only two (0.8%) were seropositive for HIV. This indicates the risk of vertical or materno-fetal HIV transmission in our community and underscores the need for urgency for prospective monitoring of infants born to HIV seropositive women.

CONCLUSION

Although the prevalence rate of HIV seropositivity amongst the otherwise healthy Nigerian pregnant women is only 0.8%, we advocate universal screening of HIV during pregnancy.

A comparison of human immunodeficiency virus (HIV) seropositivity and hepatitis B surface antigenemia (HBs Ag) among the same group of apparently healthy pregnant women in Lagos, Nigeria: a preliminary report

Two hundred and fifty apparently healthy pregnant women attending the Obstetrics and Gynecology Clinic of the Lagos University Teaching Hospital (LUTH), Lagos, Nigeria were screened for a comparison of the prevalence of HIV seropositivity and hepatitis B surface antigenemia (HBs Ag) amongst them. The Karpas AIDS cell test for HIV seropositivity and Bioman Hepatitis test kits were used as described by the manufacturers. HIV seropositive cases were confirmed using the Western blot test. Results revealed that out of the 250 pregnant women screened, 2 (0.8%) and 11 (4.4%) were HIV-1 and HBs Ag seropositive, respectively. However, the same 2 pregnant women now constituting 2 (18.2%) of the 11 HBs Ag positive pregnant women were simultaneously HIV-1 seropositive. Antibody to HIV-2 was not recorded in all HIV seropositive cases. This is the first report on the simultaneous prevalence of HBs Ag and HIV seropositivity among apparently healthy pregnant women in Lagos, Nigeria.

Isolation of a novel cytotoxic lymphokine (factor 2) from a human B-cell line (Karpas 160b) by preparative isoelectric focusing in the rotofor cell and chromatofocusing

Preparative isoelectric focusing (IEF) using a Rotofor cell was used for the isolation of a biologically active form of a novel cytotoxic lymphokine (Factor 2, F2) produced by a human B-cell line (Karpas 160b). We found that F2 either purified by DE52 or extracted from 160b cells using CHAPS, after adding octyl glucoside to 0.05%, could be electrofocused in the Rotofor cell without the addition of carrier ampholytes. Better recovery and separation were also achieved in the presence of 0.5% CHAPS, 3M urea. We compared the fractionation of F2 by chromatofocusing and IEF in Rotofor. Our results also showed that F2 was separable from tumor necrosis factor and phorbol myristate acetate-associated cytotoxicity by one step IEF in Rotofor. F2 purified by DE52, S-300 and Mono Q was further purified by IEF in Rotofor.

Multiparameter flow cytometric analysis of a novel cytotoxin (factor 2) induced tumor cell membrane permeability

An improved twin-probe multiparameter flow cytometric technique was applied to examine a novel cytotoxin, Factor (F2), induced tumor cell permeability. Ability to retain preloaded intracellular bis-carboxyethyl carboxyfluorescein (BCECF, green fluorescence) and to exclude extracellular propidium (red fluorescence) was measured simultaneously with forward and right-angle scatter. In addition to the two expected cell populations which were stained green negative, red positive ("membrane-damaged" and "non-viable", Region 2), and green positive, red negative ("membrane intact" and "viable", Region 3), a third population was seen which fluoresced neither green nor red and displayed intermediate light scatter characteristics (Region 1). K562 cells progressed from Region 3 to Region 1, and then from Region 1 to Region 2 after treatment with F2. These results suggest that sequential changes in membrane structure lead to increased permeability, first with respect to intracellular BCECF and then in turn to extracellular propidium. Flow cytometric changes caused by F2 were detectable 10 min after treatment with 2.5 U/ml of F2, and 5 min after 10 or 40 U/ml of F2. Flow cytometric analysis showed that F2-induced tumor cell lysis and growth inhibition were accompanied by rapid alternations in tumor cell membrane permeability. Flow cytometric analysis also distinguished F2 cytotoxicity from phorbol myristate acetate (PMA) associated cytotoxicity to K562 cells and determined that F2 produced spontaneously or induced by PMA and/or ciprofloxacin had a similar ability to induce tumor cell membrane permeability change.

Immunochemical localization of a region of chaperonin-60 important for productive interaction with chaperonin-10

An IgG1 monoclonal antibody (mAb 54G8) which binds to both Bordetella pertussis chaperonin-60 (cpn60) and Escherichia coli cpn60 (GroEL) was produced. mAb 54G8 as well as Fab fragments prepared from this antibody were found to abolish the ability of chaperonin-10 (cpn10, GroES) to inhibit the ATPase activity of both B. pertussis cpn60 and E. coli cpn60. Electron microscopy was used to localize the binding site of the monoclonal antibody on the B. pertussis cpn60 molecule. In the absence of the antibody, the B. pertussis molecule exhibited the tetradecameric structure typical of cpn60. Both end views (showing 7-fold symmetry of the face of the molecule) and side views were evident. When mAb 54G8 was bound, B. pertussis cpn60 molecules appeared to be cross-linked so that they formed long chains. Only side views of the molecules were seen in these long chains. When B. pertussis cpn60 complexed with Fab fragments of mAb 54G8 was examined, chains were no longer observed. Instead, side views of B. pertussis cpn60 were often seen with Fab fragments extending from the ends of the molecule. These data indicate that mAb 54G8 appears to bind at or near the end of the B. pertussis cpn60 molecule and that binding of mAb 54G8 at this location affects the ability of cpn10 to productively interact with cpn60, most likely either by sterically blocking the binding of cpn10, by affecting the conformation of cpn60 in such a way that it no longer binds cpn10, or by inhibiting proper transduction of the effects of cpn10 binding.

Phosphate derivatives of AZT display enhanced selectivity of action against HIV 1 by comparison to the parent nucleoside

Novel phosphate derivatives of the anti-HIV nucleoside analogue AZT have been prepared by phosphorochloridate chemistry. In particular, phosphates carrying ester-containing side-chains are described. These materials are designed to act as membrane-soluble pro-drugs of the bio-active free nucleotides. In vitro evaluation revealed the compounds to have a pronounced, selective antiviral activity. In several cases the phosphate derivatives are more selective in their action than the parent nucleoside AZT. In particular, this arises from the low toxicity of the phosphate pro-drugs by comparison to AZT. These data support the suggestion that the phosphate derivatives exert their biological effects via intracellular release of the nucleotide forms, and suggests that such pro-drug forms may be worthy of further study.

Inhibition of human immunodeficiency virus and growth of infected T cells by the immunosuppressive drugs cyclosporin A and FK 506

The effects of the immunosuppressive drugs cyclosporin A and FK 506 were studied on cells chronically infected with human immunodeficiency virus type 1 (HIV-1) as well as on uninfected and newly infected cells. When cells chronically infected with HIV-1 or with HIV-2 were cocultivated with uninfected cells in the presence of cyclosporin A or FK 506 there was a delay in the formation of syncytia and of cytopathic effects. This inhibitory effect was not due to decreased membrane expression of CD4. In addition, there was an approximately 100-fold reduction in the yield of infectious HIV-1 when the infected cells were grown in the presence of these drugs, a finding consistent with other evidence of decreased HIV expression. Both drugs were found to inhibit the growth of chronically infected cells at concentrations that did not inhibit the growth of the uninfected cells. These results, demonstrating that cyclosporin A and FK 506 interfere with HIV production and selectively inhibit the growth of infected cells, suggest that they may be useful in the treatment of this infection and indicate further cellular targets for antiviral agents.

Evolution of the primate lentiviruses: evidence from vpx and vpr

The genomes of the four primate lentiviral groups are complex and contain several regulatory or accessory genes. Two of these genes, vpr and vpx, are found in various combinations within the four groups and encode proteins whose functions have yet to be elucidated. Comparison of the encoded protein sequences suggests that the vpx gene within the HIV-2 group arose by the duplication of an ancestral vpr gene within this group. Evolutionary distance analysis showed that both genes were well conserved when compared with viral regulatory genes, and indicated that the duplication occurred at approximately the same time as the HIV-2 group and the other primate lentivirus groups diverged from a common ancestor. Furthermore, although the SIVagm vpx proteins are homologous to the HIV-2 group vpx proteins, there are insufficient grounds from sequence analysis for classifying them as vpx proteins. Because of their similarity to the vpr proteins of other groups, we suggest reclassifying the SIVagm vpx gene as a vpr gene. This creates a simpler and more uniform picture of the genomic organization of the primate lentiviruses and allows the genomic organization of their common precursor to be defined; it probably contained five accessory genes: tat, rev, vif, nef and vpr.

Production and induction of a novel cytotoxin (factor 2) by a human B-cell line

The human B-cell line, Karpas 160, was found to produce Factor 1 and 2 (F1 and F2). F1 was found to be indistinguishable from tumor necrosis factor beta (TNF-beta), while F2 appears to be a new cytotoxin. We used several stimuli alone or in combination to trigger the 160b cells, a subclone of Karpas 160, to produce higher yield of F2. The optimal culture times, concentrations of cells and a range of stimuli were studied. We found that 20-25 ng/ml of phorbol myristate acetate (PMA) effectively induced the higher production of F2. Pretreatment of the cells with sodium butyrate enhanced F2 production. Production of TNF but not F2 was inhibited when the cells were cultured with tunicamycin and PDB. When ciprofloxacin or cycloheximide was added to the medium, F2 production in the presence of PMA was amplified. When 160b cells were cocultured with K562 cells, low levels of F2 induction were observed. We found that most types of human tumor cell lines were highly susceptible to F2, but less sensitive or even resistant to TNF. In contrast, normal human cell lines were not susceptible to F2. Therefore, it appears that F2 could be a new human cytotoxin.

Relationship between a novel human cytotoxin (factor 2) produced by a B cell line (Karpas 160) and phorbol-myristate-acetate-associated cytotoxicity

We found that 160b cells, a subclone of Karpas 160 human B cell line, spontaneously secreted a novel cytotoxin, factor 2 (F2). F2 was also extracted from the cells by 60% ammonium sulphate, 0.5% CHAPS and 0.28% Triton X-114. We were able to show that phorbol myristate acetate (PMA) greatly enhanced the production of F2, and PMA may also account for part of the putative F2 cytotoxic activity to K562 cells in crude preparations. We compared the cytotoxic effect of F2 with PMA-associated F2-like cytotoxicity to K562 cells as well as the adequacy of our schemes to purified F2 with regard to its separation from PMA. We found that it was possible to separate PMA from F2 preparations by gel filtration and Rotofor preparative isoelectric focusing. The fate of PMA was also monitored with 3H-PMA and chromatographic profiles of 3H-PMA were studied using DE52 and gel filtration chromatography. We were able to establish that less than 2.9% of the cytotoxicity to K562 was due to PMA. We also found that the radioactive peaks and cytotoxicity peaks to K562 were not well correlated, indicating that the cytotoxicity was not mainly due to remaining PMA. Activated charcoal removed virtually all F2 and PMA but not tumour necrosis factor activity. Our results also showed that cytotoxicity to K562 resulting from F2 or PMA-associated proteins had different physicochemical properties, indicating that they are different molecular entities. These findings are consistent with the earlier observation that 160 cells produce F2 spontaneously and that PMA can amplify its production significantly.

Characterization and partial purification of a novel cytotoxic lymphokine (factor 2) produced by a human B cell line (Karpas 160)

A subclone (160b) of the human B cell (Karpas 160) was shown to produce a novel cytotoxic lymphokine [Factor 2 (F2)] in addition to tumour necrosis factor alpha (TNF-alpha) and beta (TNF-beta). F2 was found to have selective toxicity to numerous human tumour cell lines, particularly the erythroleukaemic cell line K562, whereas TNF-alpha/beta were not cytotoxic to these cells, even at relatively high concentrations. Our studies have shown that F2 activity in crude preparations is heterogeneous both in its molecular weight, isoelectric point (pI) and hydrophobicity, which depends not only on the source of F2 cytotoxicity but also on the conditions of methods for its production. Our studies also showed that F2 was separable from TNF by DE52, S-300 gel filtration and Rotofor isoelectric focusing. F2 was partially purified up to 1000-fold by two procedures. The major active form, as assessed by gel filtration was of mol. wt of 45-67 kDa. On SDS-PAGE, F2 activity was recovered mainly from two regions of the gels corresponding to 10-14 kDa and 60-70 kDa. Antibodies of human TNF-alpha, TNF-beta, IFN-alpha, IFN-gamma, and TGF-beta failed to prevent F2-mediated cytotoxicity to K562. F2 activity was not inhibited by mannose-6-PO4 or mouse mAb to rat granule content, both of which have been reported to block human natural killer cytotoxic factor. Our studies indicated that F2 is likely to be a distinct human cytokine with selective cytotoxic activity against tumour cells.

Oligonucleotide primers for polymerase chain reaction amplification of human immunoglobulin variable genes and design of family-specific oligonucleotide probes

In recent work, the polymerase chain reaction (PCR) has been used to amplify rearranged mouse and human immunoglobulin heavy and kappa light chain variable (V) genes. Here we have optimized the design of the PCR primers for human V genes and used them to amplify cDNA from human peripheral blood lymphocytes. Cloning and sequencing revealed a diverse repertoire of V genes, and the presence of members of each human V gene family. After alignment of the sequences, we identified a region conserved within V gene families, but differing between families, and used this to design family-specific oligonucleotide probes.

Nucleotide sequence of a Guinea-Bissau-derived human immunodeficiency virus type 2 proviral clone (HIV-2CAM2)

We report the complete nucleotide sequence of a human immunodeficiency virus type 2 (HIV-2) isolate from Guinea-Bissau (HIV-2CAM2). The genomic organization of HIV-2CAM2 is identical to that of other HIV-2 isolates but contains a stop codon in the pol gene. The deduced amino acid sequences of the viral proteins show variation of 20% in the gag, pol and vpx regions, and 25 to 45% in the tat, env and nef regions when compared to other isolates of HIV-2. This is greater than the variation observed between isolates of HIV-1.

Polymerase chain reaction evidence for human immunodeficiency virus 1 neutralization by passive immunization in patients with AIDS and AIDS-related complex

We tried to assess the long-term safety and potential efficacy of passive immunization in AIDS-related-complex (ARC) and AIDS patients. We also wanted to establish whether hyperimmune plasma from healthy human immunodeficiency virus 1 (HIV-1)-infected individuals clears the cell-free virus from circulation. Using the polymerase chain reaction (PCR), we were able to provide conclusive evidence that hyperimmune plasma is effective and maintains long-term neutralization of viremia. Using the cell test, we found that in most patients the total antibody level was maintained; in one of the ARC patients, it actually increased 8-fold and has remained at that level for nearly 2 years. The CD4+ cell count decreased in the AIDS patients but was stable in the ARC patient. Clinically, there was an initial improvement in all patients, but five of six of the advanced/terminal AIDS patients had died by month 17. Our studies suggest that passive immunization may be safe in ARC and AIDS patients. It reduces HIV-1 viremia to levels undetectable even by PCR. To advanced/terminal patients, the benefit is of limited duration, while to ARC patients it may be long-term. Therefore, passive immunization should start early in the disease.

A new human B-cell non-Hodgkin's lymphoma cell line (Karpas 422) exhibiting both t (14;18) and t(4;11) chromosomal translocations

A unique B-cell non-Hodgkin's lymphoma (NHL) cell line (Karpas 422), bearing both t(14;18) and t(4;11) chromosomal translocations as well as several other chromosomal abnormalities, has been established from the pleural effusion of a patient with chemotherapy-resistant NHL. This cell line has the same karyotypic features as malignant cells from the patient. The major cell clone is characterized chromosomally by 46,XX t(2;10)(p23;q22.1), t(4;11)(q21.3; q23.1), t(14;18)(q32.1;q21.3), t(4;16)(q21.3;p13.1). Both phenotypically and genotypically, the cell line has features of a mature B-cell neoplasm with no evidence for commitment to other lineages. Rearrangements of the C-ETS-1 oncogene and N-CAM-1 and CD3 genes that map to 11q23 were not detected by conventional Southern analysis. BCL-2 was rearranged within the major breakpoint cluster. The K422 cell line has a unique karyotype; this is the first occasion that the t(4;11) translocation has been described in a t(14;18) lymphoma. The cell line will be of value in determining the molecular nature of the t(4;11) translocation.

A new human plasma cell line, Karpas 620, with translocations involving chromosomes 1, 11 and 14

We report here the establishment of a new cell line, Karpas 620 (K620), from the peripheral blood of an elderly woman with an IgG-kappa plasma cell leukaemia (PCL). The line has the same hypotetraploid karyotype as the fresh cells from the patient. The cultured cells have the ultrastructural appearance of plasma cells with abundant rough endoplasmic reticulum (RER) and secrete kappa light chain. They are positive for surface antigens HLA DR, and WR17 (CD 37) and negative for CD1, CD3, CD4 and CD8. Using high resolution (HR) cytogenetic analysis it has been possible to identify all the marker chromosomes including several rearrangements commonly seen in malignancies of B cell lineage. These are a 14q+ marker with a typical 'Burkitt' morphology der(14)(pter----q32.3::8q24.1----qter) but with no reciprocal 8q-, and three translocations involving chromosome 11 at q13 with partners other than chromosome 14, namely 1q32.1, 8q24.22 and 13q14.3. An earlier report of molecular studies on the DNA of K620 has shown a rearrangement near the region on 11q13 designated BCL-1 (Rabbitts et al. 1988). This is the first report of a rearrangement in the region of 11q13 in a cell line originating from a case of plasma cell leukaemia.