Cloned human and mouse kappa immunoglobulin constant and J region genes conserve homology in functional segments

Immunoglobulins or Antibodies: IMGT® Bridging Genes, Structures and Functions

IMGT®, the international ImMunoGeneTics® information system founded in 1989 by Marie-Paule Lefranc (Université de Montpellier and CNRS), marked the advent of immunoinformatics, a new science at the interface between immunogenetics and bioinformatics. For the first time, the immunoglobulin (IG) or antibody and T cell receptor (TR) genes were officially recognized as 'genes' as well as were conventional genes. This major breakthrough has allowed the entry, in genomic databases, of the IG and TR variable (V), diversity (D) and joining (J) genes and alleles of Homo sapiens and of other jawed vertebrate species, based on the CLASSIFICATION axiom. The second major breakthrough has been the IMGT unique numbering and the IMGT Collier de Perles for the V and constant (C) domains of the IG and TR and other proteins of the IG superfamily (IgSF), based on the NUMEROTATION axiom. IMGT-ONTOLOGY axioms and concepts bridge genes, sequences, structures and functions, between biological and computational spheres in the IMGT® system (Web resources, databases and tools). They provide the IMGT Scientific chart rules to identify, to describe and to analyse the IG complex molecular data, the huge diversity of repertoires, the genetic (alleles, allotypes, CNV) polymorphisms, the IG dual function (paratope/epitope, effector properties), the antibody humanization and engineering.

Preferential combination between the light and heavy chain isotypes of fish immunoglobulins

Immunoglobulin light chain (IgL) is necessary for the assembly of an Ig molecule, which plays important roles in the immune response. IgL genes were identified in various teleost species, but the basic functions of different IgL isotypes and the preferential combination between IgL and IgH (Ig heavy chain) isotypes remain unclear. In the current study, by EST database searching and cDNA cloning in rainbow trout, 8 IgL sequences were obtained, which could be classified into the IgLκF, IgLκG, IgLσ and IgLλ isotypes, respectively. Trout IgL isotypes were highly expressed in the immune-related tissues, and participated in the immune responses in spleen and gut by stimulation with LPS and poly (I:C). The results of FACS and LC-MS/MS indicated that the IgLκG and IgLσ isotypes preferentially bonded with the heavy chains of IgM and IgT, respectively, in trout B cells and serum. In addition, the genomic organization of trout IgL isotypes and the utilization of recombination signal sequences were studied.

Expression and characterization of an enantioselective antigen-binding fragment directed against α-amino acids

This work describes the design and expression of a stereoselective Fab that possesses binding properties comparable to those displayed by the parent monoclonal antibody. Utilizing mRNA from hybridoma clones that secrete a stereoselective anti-l-amino acid antibody, a corresponding biotechnologically produced Fab was generated. For that, appropriate primers were designed based on extensive literature and databank searches. Using these primers in PCR resulted in successful amplification of the VH, VL, CL and CH1 gene fragments. Overlap PCR was utilized to combine the VH and CH1 sequences and the VL and CL sequences, respectively, to obtain the genes encoding the HC and LC fragments. These sequences were separately cloned into the pEXP5-CT/TOPO expression vector and used for transfection of BL21(DE3) cells. Separate expression of the two chains, followed by assembly in a refolding buffer, yielded an Fab that was demonstrated to bind to l-amino acids but not to recognize the corresponding d-enantiomers.

Decreased chimeric antibody productivity of KR12H-1 transfectoma during long-term culture results from decreased antibody gene copy number

The stability of KR12H-1 transfectoma in regard to chimeric antibody production was examined during long-term, repeated batch culture without selection pressure using antibiotics. Both serum-supplemented and serum-free media were used. Regardless of the medium used, the specific antibody productivity (q(Ab)) of transfectoma decreased by 60% to 88% during 70-day culture. This loss of antibody productivity was not due mainly to the appearance of a nonproducing population (NP) of transfectoma. The percentage of a producing population (P), which was monitored by the limiting dilution method, remained over 90% until the end of culture, indicating that the q(Ab) of P decreased during the culture. Flow cytometric data also showed the increase of cell population with low fluorescence intensity during culture, indicating that the intracellular antibody content of P decreased. The subclones of P obtained at the end of long-term culture were further characterized. Compared with the q(Ab) of P at the beginning of long-term culture, the q(Ab) of most P subclones was significantly low, confirming that the loss of antibody productivity was due mainly to the decreased q(Ab) of P during long-term culture. The decreased antibody gene copy number of P subclones was found to be partly responsible for the decreased q(Ab) of P during long-term culture. (c) 1996 John Wiley & Sons, Inc.

Evolution of the porcine (Sus scrofa domestica) immunoglobulin kappa locus through germline gene conversion

Immunoglobulin (IG) gene rearrangement and expression are central to disease resistance and health maintenance in animals. The IG kappa (IGK) locus in swine (Sus scrofa domestica) contributes to approximately half of all antibody molecules, in contrast to many other Cetartiodactyla, whose members provide the majority of human dietary protein and in which kappa locus utilization is limited. The porcine IGK variable locus is 27.9 kb upstream of five IG kappa J genes (IGKJ) which are separated from a single constant gene (IGKC) by 2.8 kb. Fourteen variable genes (IGKV) were identified, of which nine are functional and two are open reading frame (ORF). Of the three pseudogenes, IGKV3-1 contains a frameshift and multiple stop codons, IGKV7-2 contains multiple stop codons, and IGKV2-5 is missing exon 2. The nine functional IGKV genes are phylogenetically related to either the human IGKV1 or IGKV2 subgroups. IGKV2 subgroup genes were found to be dominantly expressed. Polymorphisms were identified on overlapping BACs derived from the same individual such that 11 genes contain amino acid differences. The most striking allelic differences are present in IGKV2 genes, which contain as many as 16 amino acid changes between alleles, the majority of which are in complementarity determining region (CDR) 1. In addition, many IGKV2 CDR1 are shared between genes but not between alleles, suggesting extensive diversification of this locus through gene conversion.

In situ visualisation of immunoglobulin genes in normal and malignant lymphoid cells

Aims-To directly visualise immunoglobulin (Ig) heavy (H) and light chain genes (kappa and lambda) in metaphase chromosomes and interphase nuclei of normal and malignant lymphocytes using small genomic probes targeted to intragenic sequences.Methods-Cytogenetic preparations from phytohaemagglutinin stimulated lymphocytes, B-chronic lymphocytic leukaemia (B-CLL) cells, and a B-prolymphocytic leukaemia (B-PLL) cell line, containing a t(11;14), were hybridised in situ using biotin or digoxigenin labelled plasmid probes. The kappa genes were visualised with a combination of probes for the Ckappa, Jkappa, Vkappa1, and Vkappa2 segments, the lambda genes with a probe containing the Jlambda2-Clambda2, Jlambda3-Clambda3 segments and the H genes with a probe for Clambda2. Hybridisation sites were visualised using appropriate fluorochrome conjugates and images were analysed by digital microscopy.Results-In both normal and malignant lymphoid cells, the kappa and lambda genes were visualised as a single dot signal, whereas the H lambda genes were resolved as either two or three separate signals per chromatid in metaphase chromosomes or per allele in interphase nuclei. In the malignant PLL cells, double hybridisation experiments with a painting library specific for the chromosome 11 showed that the lambda region was retained in the translocated chromosome, with an in situ resolution pattern similar to that of the normal allele.Conclusions-This study shows that a high resolution in situ analysis of the three Ig loci can be efficiently performed with small size genomic probes on both normal and malignant lymphoid cells. Such an approach offers a flexible tool for the molecular characterisations of these loci on chromosomes and individual neoplastic cells.

Nomenclature of the human immunoglobulin genes

The human immunoglobulins (Ig) are the products of three unlinked sets of genes: the immunoglobulin heavy (IGH), the immunoglobulin kappa (IGK), and the immunoglobulin lambda (IGL) genes, localized on chromosome 14 (14q32.33), 2 (2p12), and 22 (22q11.2), respectively. This appendix presents tabulated lists of the human immunoglobulin heavy, kappa, and lambda genes named in accordance with the International ImMunoGeneTics database (IMGT) and approved by the Human Genome Organization (HUGO) Nomenclature Committee in 1999. Three additional tables list corresponding nomenclatures for these genes.

High level expression of a functional human/mouse chimeric anti-CD20 monoclonal antibody in milk of transgenic mice

Rituximab, a chimeric anti-CD20 monoclonal antibody, is one of the most successful biomedicines and has been used to treat at least 370,000 patients with indolent, aggressive non-Hodgkin's lymphoma and other malignant diseases. However, the global demand for rituximab and other therapeutic monoclonal antibodies is exponentially increasing and barely able to be met by current manufacturing capacities of mammalian cell culture. The mammary gland bioreactor has been regarded as an ideal substitute for mammalian cell culture to mass-produce recombinant monoclonal antibodies at the lowest possible cost. Here, we show a feasible model to produce recombinant anti-CD20 antibodies in the mammary glands of transgenic animals. Six lines of transgenic mice were generated by co-microinjection of the two expression cassettes that can specially express the chimeric light and heavy chain of anti-CD20 mAbs in the milk of transgenic animals. The recombinant antibodies were detected in the milk of transgenic mice with the highest expression level up to 17 microg/mul and could specifically bind the CD20 surface antigens on human B-lymphoma cells.

Genomic organization of the immunoglobulin light chain gene loci in Xenopus tropicalis: evolutionary implications

Based on presently available genome data, we characterized the genomic organization of all three light chain gene (rho, sigma and type III) loci in Xenopus tropicalis. The rho gene locus in X. tropicalis, structurally similar to the kappa gene loci in mammals, was shown to contain a single C rho gene and nine J rho segments. The sigma locus also contains a single C gene, although two distinct C sigma genes have previously been found in Xenopus laevis (most likely due to chromosome polyploidy). Four J sigma gene segments were identified upstream of the C sigma. The type III light chain gene locus, spanning approximately 170 kb DNA, structurally resembles the topology of mammalian lambda gene loci, containing three C genes (C III 1-3). C III 2 and C III 3 are both preceded by single, unique, J genes, whereas C III 1 contains three J gene segments. Furthermore, two additional J gene segments, termed J III x1 and J III x2, were found in the intron separating V III 2 and pV III 1 (a pseudogene). Based on BLAST searches against the X. tropicalis EST database, all the C genes identified in this study were shown to be functional. On the basis of similarity of protein sequences, genomic organization and chromosomal location of the light chain genes among frogs and mammals, our data strongly support the previous suggestions that the rho genes belong to the kappa gene lineage, whereas the type III genes share a common origin with the lambda genes.

Binding activities and antitumor properties of a new mouse/human chimeric antibody specific for GD2 ganglioside antigen

PURPOSE

We previously generated a mouse monoclonal antibody (mAb) specific for the tumor-associated GD2 ganglioside antigen. Here, we describe the development of a chimeric anti-GD2 mAb for more effective tumor immunotherapy.

EXPERIMENTAL DESIGN

We cloned the cDNA encoding the immunoglobulin light and heavy chains of the 60C3 anti-GD2 mAb, and constructed chimeric genes by linking the cDNA fragments of the variable regions of the murine light and heavy chains to cDNA fragments of the human kappa and gamma1 constant regions, respectively.

RESULTS

The resultant chimeric anti-GD2 mAb, c.60C3, showed identical binding affinity and specificity to that of its murine counterpart. Both c.60C3 and 60C3 were rapidly internalized by tumor cells at 37 degrees C. When human serum and human natural killer cells were used as effectors in complement-mediated cytotoxicity and antibody-dependent cell cytotoxicity, respectively, c.60C3 was more effective in killing GD2-expressing tumor cells. However, c.60C3 was ineffective at inducing cell death by apoptosis, although binding of 60C3 induced apoptotic death in vitro. In an in vivo, GD2-expressing, syngeneic tumor model, i.v. injection of c.60C3, but not of 60C3, significantly suppressed tumor growth in mice (P<0.0005).

CONCLUSION

Immune effector functions mediated by this antibody and its potentially reduced immunogenicity make chimeric c.60C3 a promising therapeutic agent against neuroectodermic tumors.

Chemiluminescent detection of clonal immunoglobulin and T cell receptor gene rearrangements in Tunisian lymphoid malignancies, leukemias and lymphomas

Clonal rearrangement of antigen receptor genes is commonly used to characterize the lymphoproliferative diseases. In order to perform molecular characterization in the diagnostics and monitoring of lymphoid malignancies, leukemias and lymphomas in Tunisia, we have introduced the use of chemiluminescent probes for immunoglobulin (IG) and T cell receptor (TR) gene rearrangement detection employing the Southern blot method. The chemiluminescent and radioactive detection methods tested with alkaline phosphatase and 32P labelled probes, respectively, were used for the IG and TR gene rearrangement characterization. Our results show the same pattern of rearrangement. Moreover, the chemiluminescent signal is detected faster and it is as sensitive as the radioactive one. We report the optimized conditions for using IGH, IGK, IGL, TRB and TRG probes in non radioactive detection. We have applied the chemiluminescent Southern blot method to analyze examples of Tunisian leukemias and lymphomas. The results allowed the assessment of clonality and the T or B cell lineage of these cases. The use of non radioactive probes makes chemiluminescent Southern blot detection reliable, safe and sensitive. As the use of radioactivity is not common in our laboratories and the licensing requirements needed for its use prohibitive, the chemiluminescent technique will be of great help for detection and characterization of molecular markers in lymphoid malignancies in Tunisia.

Protection of mice against Human respiratory syncytial virus by wild-type and aglycosyl mouse–human chimaeric IgG antibodies to subgroup-conserved epitopes on the G glycoprotein

Monoclonal antibodies (mAbs) to conserved epitopes on the G glycoprotein of human respiratory syncytial virus (HRSV) subgroup A fail to neutralize the virus in cell culture in the absence of complement, but are protective in rodent models of infection. They may have potential as prophylactic agents in human infants. In order to investigate the role of Fc-dependent pathways in protection by one such antibody, 1C2, the VH and VL genes were isolated by RT-PCR and assembled with human κ light-chain and human γ1 heavy-chain constant-region genes to form two mouse–human chimaeras, which were expressed in NS0 cells. One of the chimaeras carried a wild-type γ1 chain, whilst the other had an aglycosyl mutation in the CH2 domain rendering the antibody defective in complement activation and FcγR binding. Whilst both chimaeric antibodies exhibited similar avidity for HRSV in ELISA, only the fully glycosylated wild type was capable of neutralizing the virus in the presence of complement. In mice passively immunized with either murine or wild-type γ1 chimaeric antibody, no virus could be recovered from the lungs 4 days after intranasal inoculation of HRSV. In mice immunized with the aglycosyl γ1 chimaera, however, virus was present in the lungs following challenge, although virus titres were significantly reduced compared with controls (P<0·005). These results indicate that the protective effect of this antibody is mediated by both Fc-dependent and Fc-independent pathways.

Thermodynamic stability of a kappaI immunoglobulin light chain: relevance to multiple myeloma

Immunoglobulin light chains have two similar domains, each with a hydrophobic core surrounded by beta-sheet layers, and a highly conserved disulfide bond. Differential scanning calorimetry and circular dichroism were used to study the folding and stability of MM-kappaI, an Ig LC of kappaI subtype purified from the urine of a multiple myeloma patient. The complete primary structure of MM-kappaI was determined by Edman sequence analysis and mass spectrometry. The protein was found to contain a cysteinyl post-translational modification at Cys(214). Protein stability and conformation of MM-kappaI as a function of temperature or denaturant conditions at pH 7.4 and 4.8 were investigated. At pH 4.8, calorimetry demonstrated that MM-kappaI undergoes an incomplete, cooperative, partially reversible thermal unfolding with increased unfolding temperature and calorimetric enthalpy as compared to pH 7.4. Secondary and tertiary structural analyses provided evidence to support the presence of unfolding intermediates. Chemical denaturation resulted in more extensive protein unfolding. The stability of MM-kappaI was reduced and protein unfolding was irreversible at pH 4.8, thus suggesting that different pathways are utilized in thermal and chemical unfolding.

The production and characterisation of a chimaeric human IgE antibody, recognising the major mite allergen Der p 1, and its chimaeric human IgG1 anti-idiotype

BACKGROUND

Two mouse monoclonal antibodies have been described, namely: mAb 2C7 (IgG2bkappa), which is directed against the major house dust mite allergen Der p 1, and mAb 2G10 (IgG1kappa), which is an anti-idiotypic antibody raised against mAb 2C7. Given its broad IgE specificity, anti-idiotype mAb 2G10 could potentially have immunomodulatory applications. For example, a chimaeric human IgG version of mAb 2G10 could prove to be a useful molecule for binding to mast cell and basophil FcepsilonRI bound IgE, and in doing so co-ligating FcepsilonRI with FcgammaRIIB, which has been reported to have downregulatory effects.

AIMS

To produce a chimaeric human IgE version of mAb 2C7 (mAb 2C7huE) and a chimaeric human IgG1 version of its anti-idiotype mAb 2G10 (mAb 2G10huG1).

METHODS

The Vkappa and VH regions of mAb 2C7 and its anti-idiotype mAb 2G10 were engineered into human constant regions of the IgE and IgG1 isotypes, respectively.

RESULTS

The production of chimaeric mAb 2C7huE and its anti-idiotype mAb 2G10huG1 confirmed that the respective mouse antibody V regions were successfully engineered into human constant regions and still retained the specificity of the original murine V regions.

CONCLUSION

The newly constructed chimaeric antibodies will be useful to investigate the downregulation of IgE mediated hypersensitivity by the crosslinking of FcepsilonRI with FcgammaRIIB.

Identification and location of a cysteinyl posttranslational modification in an amyloidogenic kappa1 light chain protein by electrospray ionization and matrix-assisted laser desorption/ionization mass spectrometry

Amyloid-deposited light chain (AL) amyloidosis is correlated with the overproduction of a monoclonal immunoglobulin light chain protein by a B-lymphocyte clone. Since the amyloid fibril deposits in AL amyloidosis most often consist of the N-terminal fragments of the light chain, the majority of studies have focused on the determination of the primary structure of the protein, and reducing agents have been used routinely in the initial purification process. In this study, two light chain proteins were isolated and purified, without reduction, from the urine of a patient diagnosed with kappa 1 (kappa1) AL amyloidosis. One protein had a relative molecular mass of 12,000 and the other 24,000. Electrospray ionization and matrix-assisted laser desorption/ionization mass spectrometry, in combination with enzymatic digestions, were used to verify the amino acid sequences and identify and locate posttranslational modifications in these proteins. The 12-kDa protein was confirmed to be the N-terminal kappa1 light chain fragment (variable region) consisting of residues 1-108 or 1-109 and having one disulfide bond. The 24-kDa protein was determined to be the intact kappa1 light chain containing a cysteinyl posttranslational modification at Cys214 and disulfide bonds located at Cys23-Cys88, Cys134-Cys194, and Cys214-Cys. The methods used in this report enable high-sensitivity determination of amino acid sequence and variation in intact and truncated light chains as well as posttranslational modifications. This approach facilitates consideration of the effect of cysteinylation on the native protein structure and the potential involvement of this modification in AL amyloidosis.

The distribution of somatic H1 subtypes is non-random on active vs. inactive chromatin: distribution in human fetal fibroblasts

Chromatin immunoprecipitation was employed to determine whether or not the previously reported depletion of histone H1 on actively transcribed sequences was selective with respect to H1 subtypes. DNA of immunofractionated chromatin was analyzed by slot-blots for repetitive sequences and PCR for single and low-copy sequences. Based on the analysis of a diverse set of sequences, we report distinct differences in subtype distributions. Actively transcribed chromatin, as well as chromatin poised for transcription, is characterized by a relative depletion of somatic H1 subtypes 2 and 4 (H1s-2 and H1s-4),whereas facultative and constitutive heterochromatin contain all four somatic subtypes. These results support a model in which subtypes are selectively depleted upon gene expression. In turn, the data also support the possibility that the somatic subtypes have different functional roles based on their selective depletion from different classes of DNA sequences.

Hsp70 and antifibrillogenic peptides promote degradation and inhibit intracellular aggregation of amyloidogenic light chains

In light chain (LC) amyloidosis an immunoglobulin LC assembles into fibrils that are deposited in various tissues. Little is known about how these fibrils form in vivo. We previously showed that a known amyloidogenic LC, SMA, can give rise to amyloid fibrils in vitro when a segment of one of its beta sheets undergoes a conformational change, exposing an Hsp70 binding site. To examine SMA aggregation in vivo, we expressed it and its wild-type counterpart, LEN, in COS cells. While LEN is rapidly oxidized and subsequently secreted, newly synthesized SMA remains in the reduced state. Most SMA molecules are dislocated out of the ER into the cytosol, where they are ubiquitinylated and degraded by proteasomes. A parallel pathway for molecules that are not degraded is condensation into perinuclear aggresomes that are surrounded by vimentin-containing intermediate filaments and are dependent upon intact microtubules. Inhibition of proteasome activity shifts the balance toward aggresome formation. Intracellular aggregation is decreased and targeting to proteasomes improved by overexpression of the cytosolic chaperone Hsp70. Importantly, transduction into the cell of an Hsp70 target peptide, derived from the LC sequence, also reduces aggresome formation and increases SMA degradation. These results demonstrate that an amyloidogenic LC can aggregate intracellularly despite the common presentation of extracellular aggregates, and that a similar molecular surface mediates both in vitro fibril formation and in vivo aggregation. Furthermore, rationally designed peptides can be used to suppress this aggregation and may provide a feasible therapeutic approach.

Virolysis and in vitro neutralization of HIV-1 by humanized monoclonal antibody hNM-01

Antibody humanization by transplanting the complimentarity determining region (CDR) to a human framework aims to reduce the response of the human immune system against a foreign molecule during passive immunization. We transferred the CDR from the murine monoclonal antibody (MAb) NM-01 to a human IgG frame. The humanized NM-01 (hNM-01) recognizes the same epitope on Human Immunodeficiency Virus type 1 (HIV-1) envelope as its murine progenitor, but with greater efficiency, and shows enhanced neutralization of HIV-1. We have shown that this increase in reactivity may be attributed to residue 4 of the humanized kappa chain, where the presence of a methionine residue rather than the murine leucine appears to promote a more advantageous conformation of the antigen-binding site, perhaps via packing interactions with the V(kappa) CDR1. The capacity of humanized NM-01 to neutralize direct clinical isolates was also examined with the expectation that hNM-01 will prove suitable for development as a therapeutic agent. This reshaped antibody reacted with several clinical isolates of HIV-1 tested. Moreover, we proved the ability of this antibody of its activation of complement by flow cytometry and electron microscopy analysis. Although hNM-01 alone was capable of neutralizing HIV-1, the presence of complement enhanced neutralization. The enhancement of complement activation was also observed in hNM-01 than murine progenitor. This finding supports a potential role for antibody-dependent complement-mediated virolysis and more effective neutralization in HIV-1 therapy.

Human and murine immunoglobulin expression vector cassettes

We describe the construction of new immunoglobulin (Ig) expression vectors and their use in the production of recombinant chimeric Ig molecules in transfected mammalian cells. The vectors contain the cDNA encoding the constant regions of human (mu, alpha1, gammal, gamma2, gamma3, gamma4, kappa) and murine (mu, gamma2a, kappa) Ig heavy and light chains. Unique restriction sites flanking the Ig variable region allow for replacement of variable regions generated by PCR. The CMV promoter allows for the transfection and expression of Ig in non-lymphoid cells. Distinct drug selection markers for heavy chain and light chain expression vectors allows for sequential or co-transfection of the vectors. We show that secretion of recombinant Ig can reach 1.2 microg/ml per million cells per day for transfected B cells. Replacement of the variable region results in the production of functional Ig retaining antigen specificity.

Distribution and phenotype of Epstein-Barr virus-infected cells in inflammatory bowel disease

Little is known about Epstein-Barr virus (EBV) infection of colon mucosa, particularly in inflammatory bowel diseases. Crohn's disease and ulcerative colitis are thought to differ in T-helper lymphocyte composition and cytokine secretion patterns. Some of the implicated cytokines are growth factors for EBV-infected cells. We examined colon mucosa for differences in the distribution and phenotype of EBV-infected cells. Colon tissues with Crohn's disease (n = 31) or ulcerative colitis (n = 25) and controls (n = 60) were characterized by in situ hybridization and immunohistology for six EBV gene products as indicators of latent and replicative EBV infection. The cells were additionally phenotyped by combined detection of the EBV transcripts and B- or T-cell antigens. B lymphocytes predominated as the site of latent EBV infection in the colon and were most numerous in ulcerative colitis. In active ulcerative colitis, EBV-positive lymphocytes accumulated under and within the epithelium and displayed evidence for replicative infection. The patterns of mucosal EBV gene expression indicate local impairment of virus-specific T-cell responses in active ulcerative colitis. Detection of EBV may help to discriminate between active ulcerative colitis and other inflammatory bowel diseases. Colon mucosa is a potential site of EBV replication and may be relevant for EBV transmission.

Gamma heavy chain disease in man: independent structural abnormalities and reduced transcription of a functionally rearranged lambda L-chain gene result in the absence of L-chains

Human Ig heavy chain diseases of the alpha and gamma classes are characterized by the absence of light chain production as well as the disease-defining abnormalities in the heavy chain protein. Prior studies have suggested concomitant structural defects in productively rearranged L-chain genes as the reason for the absent L-chain proteins. We have found that the single rearranged lambda L-chain gene in the OMM heavy chain disease (HCD) cell line has a mutation in the splice donor site at the 3' end of the J exon, resulting in direct splicing of the 3' end of the leader to the acceptor site of the constant region. The cells contain an mRNA consisting of the leader-coding region joined directly to the constant region. The V-region exon is skipped and the shortened mRNA is translated into a truncated protein containing no V-region amino acids. We have also noted that, in contrast to most normal and neoplastic Ig-producing cells, the OMM cells produce an excess of heavy to light chain mRNA as well as protein. The excess is independent of the structural gene abnormality and is due to a low level of L-chain transcription, which can be increased by fusing the HCD cell to the murine myeloma cell line NS-1 or transfecting the defective OMM L-chain gene into a murine plasma cell. The latter data suggest that the OMM cells either lack a transcription factor present in mature plasma cells or have a functional repressor of L-chain transcription.

Expression of a functional mouse-human chimeric anti-CD19 antibody in the milk of transgenic mice

Human B cell lymphomas are suitable targets for immunotherapy. Clinical trials with mouse-human chimeric B cell-specific monoclonal antibodies (mAbs) have already shown promising results. However, limitations for their use in clinical trials can be the lack of sufficient amounts and high production costs. Expression of mAbs in the mammary gland of transgenic animals provides an economically advantageous possibility for production of sufficient quantities of a promising antibody for clinical trials and beyond. In this paper, we show the feasibility of this approach, by generating transgenic mice expressing mouse-human chimeric anti-CD19 mAbs in their milk. Mouse anti-CD19 variable (V) region genes were combined with human IgG1 heavy (H) and kappa light (L) chain constant (C) region genes and fused to the bovine beta-lactoglobulin (BLG) promoter in two separate expression cassettes. Co-injection resulted in five transgenic lines. In one of these lines completely assembled chimeric mAbs were secreted into the milk, at an approximate level of 0.5 mg/ml. These mAbs were able to bind specifically to the CD19 surface antigen on human B cells.

Rapid expression cloning of human immunoglobulin Fab fragments for the analysis of antigen specificity of B cell lymphomas and anti-idiotype lymphoma vaccination

An expression system for rapid and standardized production of human recombinant immunoglobulin Fab fragments in E. coli was developed. Functional folding of the Fab fragments was accomplished by the dicistronic expression vector pFab.gammakappa containing specialized leader sequences to direct the immunoglobulin heavy and light chains to the periplasmic bacterial space. A C-terminal hexahistidine tag of the Fd chain facilitated metal affinity chromatography and purification to homogeneity as assessed by SDS PAGE and silver staining. Specific antigen recognition by a hybridoma-derived Fab fragment was indistinguishable from that of the corresponding monoclonal antibody. This protocol may be useful for analysis of the antigen specificity of human B cells and for convenient production of lymphoma-derived idiotype protein for vaccination strategies. To obtain unmodified immunoglobulin cDNA sequences from small human biopsies for insertion into pFab.gammakappa, oligo(dG)-tailed cDNA was amplified with an oligo(dC)- and nested mu or kappa constant region-specific primers. Using single sets of primers for each class of immunoglobulin transcripts, the products of this anchored PCR reflected the relative abundance of the starting cell population and permitted reliable identification of clonal, lymphoma-derived sequences for subsequent expression cloning.

A single backmutation in the human kIV framework of a previously unsuccessfully humanized antibody restores the binding activity and increases the secretion in cos cells

Humanization of rodent mAbs by CDR-grafting (also called "reshaping") is now a standard procedure for reducing immunogenicity and recruiting human effector functions. However, the design of the humanized mAb can sometimes prove circuitous. Attempts were made to humanize L-25, a mouse antibody against the human alpha-4 integrin subunit using the usual protocols. Despite reaching eight backmutations in the light chain, it was not possible to recover the binding activity to the level of the chimeric. In an effort to restore the binding activity, an analysis of the human kappa IV acceptor frameworks was undertaken. This analysis highlighted the Asp at position 9 in framework 1, which although a common amino acid in human kappa IV frameworks, was an unusual residue in mouse kappa frameworks. Backmutating this position to the mouse amino acid completely restored the binding of the humanized antibody and as a by-product also increased the secretion levels in cos cells. Mutating position 9 to the consensus residue for human kappa I also restored the binding and secretion levels although not to the same extent. The resulting humanized antibody had a light chain with only a single backmutation to the mouse sequence.

Characterization of the three immunoglobulin G subclasses of macaques

Southern blot experiments with genomic DNA samples of rhesus monkeys and crab-eating macaques and human C gamma-specific probes indicated that the two macaque species studied here possessed three C gamma genes per haploid genome. By amplifying the cDNA from macaque-mouse hybridomas, the coding sequences of two different rhesus monkey immunoglobulin (Ig)G subclasses, IgG1rh (Cgamma1rh) and IgG2rh (Cgamma2rh), and one crab-eating macaque IgG subclass IgG1mafa (Cgamma1mafa), were characterized. None of the 16 rhesus monkey-mouse hybridomas studied here secreted IgG of the third subclass IgG3rh (Cgamma3rh). The Cgamma3rh gene was partly characterized at the genomic level. The cDNA of the Cgamma3rh gene was amplified from mRNA of rhesus monkey peripheral blood mononuclear cells (PBMC). The results are analysed in terms of phylogenesis of the C gamma genes. The cDNA sequences coding for the Cmu and the Ckappa domains of rhesus monkey Ig were established and compared to their human and non-human primate counterparts.

Somatic Mutations Within the Untranslated Regions of Rearranged Ig Genes in a Case of Classical Hodgkin’s Disease as a Potential Cause for the Absence of Ig in the Lymphoma Cells

Hodgkin–Reed-Sternberg (H-RS) cells are clonal B cells carrying Ig gene rearrangements. However, in situ hybridization methods failed to demonstrate Ig gene expression in H-RS cells of classical Hodgkin’s disease (HD). Because somatic mutations rendering potentially functional Ig gene rearrangements nonfunctional were detected in some cases of the disease, it was speculated that H-RS cells in classical HD may have lost the ability to express antigen receptor as a rule. Recently, we established a novel cell line (L1236) from H-RS cells of a patient with mixed cellularity subtype of HD. L1236 cells harbor a potentially functional VH1 and a potentially functional Vκ3 gene rearrangement. However, no antibody expression was detected. To show potential reasons for this lack of Ig expression, we analyzed the genomic organization of the Ig genes and their transcription in the primary and cultivated H-RS cells of this patient. The H-RS cells were found to have switched their isotype to IgG4, confirming their mature B-cell nature. By amplifying cDNA from L1236 cells as well as from frozen biopsy material transcripts of the Vκ3 and the VH1 gene rearrangement were detected for both sources of cDNA. However, Northern blot hybridization of L1236 RNA failed to demonstrate VH1 and Vκ3 transcripts, indicating only a low level of transcription. Sequence analysis of the promoter and leader regions of the VH1 gene rearrangement from L1236 cells as well as from lymphoma-affected tissue showed a somatic mutation in the conserved octamer motif of the promoter region. Somatic mutations were also detected within the 3′ splice site of the leader intron and adjacent nucleotides in the rearranged Vκ light chain gene, leading to aberrant splicing. These mutations might prevent the generation of adequate amounts of functional Ig gene transcripts as template for translation into protein. Thus, mutations in H-RS cells that prevent Ig gene expression might also be located outside the coding region of the Ig genes.

Somatic Mutations Within the Untranslated Regions of Rearranged Ig Genes in a Case of Classical Hodgkin’s Disease as a Potential Cause for the Absence of Ig in the Lymphoma Cells

Hodgkin–Reed-Sternberg (H-RS) cells are clonal B cells carrying Ig gene rearrangements. However, in situ hybridization methods failed to demonstrate Ig gene expression in H-RS cells of classical Hodgkin’s disease (HD). Because somatic mutations rendering potentially functional Ig gene rearrangements nonfunctional were detected in some cases of the disease, it was speculated that H-RS cells in classical HD may have lost the ability to express antigen receptor as a rule. Recently, we established a novel cell line (L1236) from H-RS cells of a patient with mixed cellularity subtype of HD. L1236 cells harbor a potentially functional VH1 and a potentially functional Vκ3 gene rearrangement. However, no antibody expression was detected. To show potential reasons for this lack of Ig expression, we analyzed the genomic organization of the Ig genes and their transcription in the primary and cultivated H-RS cells of this patient. The H-RS cells were found to have switched their isotype to IgG4, confirming their mature B-cell nature. By amplifying cDNA from L1236 cells as well as from frozen biopsy material transcripts of the Vκ3 and the VH1 gene rearrangement were detected for both sources of cDNA. However, Northern blot hybridization of L1236 RNA failed to demonstrate VH1 and Vκ3 transcripts, indicating only a low level of transcription. Sequence analysis of the promoter and leader regions of the VH1 gene rearrangement from L1236 cells as well as from lymphoma-affected tissue showed a somatic mutation in the conserved octamer motif of the promoter region. Somatic mutations were also detected within the 3′ splice site of the leader intron and adjacent nucleotides in the rearranged Vκ light chain gene, leading to aberrant splicing. These mutations might prevent the generation of adequate amounts of functional Ig gene transcripts as template for translation into protein. Thus, mutations in H-RS cells that prevent Ig gene expression might also be located outside the coding region of the Ig genes.

Light chain-associated amyloid deposits comprised of a novel kappa constant domain

Light chain-associated amyloidosis is characterized by the deposition as fibrils of monoclonal light chain-related components consisting predominately of the variable domain (VL) or the VL plus up to approximately 60 residues of the constant domain (CL). Here, we describe a patient (designated BIF) with light chain-associated amyloidosis and kappa Bence Jones proteinuria in whom, notably, >80% of the amyloid deposits were comprised of CL-related material. The extracted amyloid protein consisted of 99 aa residues identical in sequence to the main portion of the Ckappa region (positions 109-207) of the precursor Bence Jones protein. Remarkably, the CLs from both molecules contained a Ser-->Asn substitution at position 177. This heretofore undescribed Ckappa alteration did not result from somatic mutation but rather was germline encoded. When tested in our in vitro fibrillogenic kinetic assay, Bence Jones protein BIF was highly amyloidogenic. Notably, endopeptidase treatment of amyloid fibrils prepared from the native light chain revealed the VL to be markedly susceptible to enzymatic digestion, whereas the CL was protease-resistant. Our findings provide evidence that the fragmented light chains typically present in this disease result from proteolytic degradation and suggest that, in this case, conformational differences in VL/CL packing within the fibrils may account for the unusual composition of the amyloid deposits. Additionally, we posit that the previously unrecognized Asn177 substitution represents yet another Ckappa allotype, provisionally designated Km4.

Immunological and molecular analysis of three monoclonal lupus anticoagulant antibodies from a patient with systemic lupus erythematosus

Antiphospholipid antibodies (APA), including lupus anticoagulants (LAC; as detected by in vitro blood clotting tests) and anti-cardiolipin antibodies (ACA; as assayed by solid-phase immunoassay), are strongly associated with recurrent thrombosis, thrombocytopenia, and recurrent fetal loss in some patients with systemic lupus erythematosus (SLE). The combined presence of APA and these clinical manifestations is termed antiphospholipid syndrome (APS). LAC and ACA comprise heterogeneous and somewhat overlapping autoantibody subsets. To date, it is unclear what degree of heterogeneity is present in an individual patient and between patients. To begin to address these issues, we generated three monoclonal LAC antibodies from a patient with SLE and APS. These antibodies were studied for their binding specificities and variable (V) region nucleotide sequences. All three LAC were unreactive with DNA, cardiolipin or other phospholipids. Sequence analysis of these antibodies revealed extensive overlap in their Ig V genes with anti-DNA antibodies and other autoantibodies characteristic of lupus. These data provide the first V gene sequence information on a group of SLE-derived LAC without ACA activity, representative of a similar subset of LAC found in patients with APS.

Humanization and Pharmacokinetics of a Monoclonal Antibody with Specificity for Both E- and P-Selectin

E- and P-selectin (CD62E and CD62P) are cell adhesion molecules that mediate leukocyte-endothelial cell and leukocyte-platelet interactions and are involved in leukocyte recruitment during inflammation. We previously developed a murine mAb, EP-5C7 (or mEP-5C7), that binds and blocks both E- and P-selectin. When used in humans, murine mAbs have short circulating half-lives and generally induce potent human anti-mouse Ab responses. We therefore engineered a humanized, complementarity determining region-grafted version of mEP-5C7 incorporating human γ4 heavy and κ light chain constant regions (HuEP5C7.g4). HuEP5C7.g4 retains the specificity and avidity of mEP-5C7, binding to human E- and P-selectin but not to human L-selectin, and blocking E- and P-selectin-mediated adhesion. Surprisingly, when administered to rhesus monkeys, HuEP5C7.g4 was eliminated from the circulation very rapidly, even faster than the original murine Ab. To isolate the cause of the short serum half-life of HuEP5C7.g4, several Ab variants were constructed. A chimeric IgG4 Ab was made by replacing the humanized V regions with murine V regions. A humanized IgG2 Ab, HuEP5C7.g2, was also made by replacing the human γ4 with a γ2 constant region. Results from pharmacokinetic studies in rhesus monkeys demonstrated that the chimeric IgG4 is also rapidly eliminated rapidly from serum, similar to the humanized IgG4 Ab, while the humanized IgG2 Ab displays a long circulation half-life, typical of human Abs.

Antigen endocytosis and presentation mediated by human membrane IgG1 in the absence of the Ig(alpha)/Ig(beta) dimer

Membrane immunoglobulin (mIg) M and D heavy chains possess minimal (KVK) cytoplasmic tails and associate with the Ig alpha/Ig beta (CD79) dimer to achieve surface expression and antigen presentation function. In contrast, the cytoplasmic tail of mIgG is extended by 25 residues (gamma ct). We have tested the possibility that mIgG can perform antigen capture and presentation functions independently of the Ig(alpha)/beta dimer. We show that CD4/(gamma)ct chimeras are efficiently endocytosed partially dependent on a tyrosine residue in (gamma)ct. In addition, human mIgG was expressed on the surface of Ig(alpha)/Ig(beta)-negative non-lymphoid cells and mediated antigen capture and endocytosis. Antigen-specific human mIgG targeted antigen to MIIC-type vesicles in the Ig(alpha)/beta negative melanoma Mel JuSo and augmented antigen presentation 1000-fold, identical to the augmentation seen in Ig(alpha)/beta-positive B-cells expressing the same transfected mIgG. Thus, unlike mIgM, mIgG has autonomous antigen capture and presentation capacity, which may have evolved to reduce or eliminate the BCR's dependence on additional accessory molecules.

The human immunoglobulin kappa locus on yeast artificial chromosomes (YACs)

The human immunoglobulin kappa locus is a duplicated structure. Contigs of 600 kb with 40 Vkappa genes and 440 kb with 36 Vkappa genes had been established for the Ckappa proximal (p) and distal (d) copies, respectively. In addition the human genome contains more than 24 dispersed Vkappa genes, called orphons. In the present study, 22 kappa-locus derived YACs were analyzed in detail, while 30 orphon-derived YACs were characterized only with respect to some parameters. The kappa-locus derived YACs allowed three gaps to be closed which previously could not be bridged by cosmid and phage lambda cloning. At the 5' side, the p contig was extended in the YACs by 50 kb and the d contig by 16 kb. At the 3'side, the d contig was extended by 11.5 kb. Beyond the 3' end of the d contig a new Vkappa gene was found, which is located, according to pulsed field gel electrophoresis (PFGE) experiments, at a distance of at least 140 kb from the last Vkappa gene of the contig. This Vkappa gene, which was termed Z0, occurred on three YACs, albeit at distances smaller than 140 kb; this was probably due to deletions in the YACs caused by abundant repetitive sequences at the borders of the locus. According to its sequence and to the restriction map of its surroundings, Z0 is an orphon gene of the so-called Z family, of which several members are known to be dispersed throughout the genome. The possibility that Z0 has been the parent of the other Z orphons is discussed.

Human B cell biology

Human B lymphocytes share one major distinctive feature with B cells of other higher animals, namely the ability to generate and secrete immunoglobulins. These highly specialized proteins are capable of tremendous diversity, and thereby account for much of our immune protection against invading organisms. Despite the great potential diversity possible in the specificities of immunoglobulin molecules, however, the binding of antibody to antigen initiates a limited spectrum of biologically important effector functions, such as complement activation and/or adherence of the immune complex to receptors on leukocytes. A variety of mechanisms have been elucidated that account for this, not all of which are shared by the different types of animals capable of making these proteins. The purpose of this chapter is to review the genetic, developmental, and physiologic mechanisms critical for human B cell expression of immunoglobulin.

Inhibition of complement activity by humanized anti-C5 antibody and single-chain Fv

Activation of the complement system contributes significantly to the pathogenesis of numerous acute and chronic diseases. Recently, a monoclonal antibody (5G1.1) that recognizes the human complement protein C5, has been shown to effectively block C5 cleavage, thereby preventing the generation of the pro-inflammatory complement components C5a and C5b-9. Humanized 5G1.1 antibody, Fab and scFv molecules have been produced by grafting the complementarity determining regions of 5G1.1 on to human framework regions. Competitive ELISA analysis indicated that no framework changes were required in the humanized variable regions for retention of high affinity binding to C5, even at framework positions predicted by computer modeling to influence CDR canonical structure. The humanized Fab and scFv molecules blocked complement-mediated lysis of chicken erythrocytes and porcine aortic endothelial cells in a dose-dependent fashion, with complete complement inhibition occurring at a three-fold molar excess, relative to the human C5 concentration. In contrast to a previously characterized anti-C5 scFv molecule, the humanized h5G1.1 scFv also effectively blocked C5a generation. Finally, an intact humanized h5G1.1 antibody blocked human complement lytic activity at concentrations identical to the original murine monoclonal antibody. These results demonstrate that humanized h5G1.1 and its recombinant derivatives retain both the affinity and blocking functions of the murine 5G1.1 antibody, and suggest that these molecules may serve as potent inhibitors of complement-mediated pathology in human inflammatory diseases.

B cell lymphoma of the thymus and salivary gland

A case of primary low grade B cell lymphoma of the salivary gland associated with a low grade B cell lymphoma of the thymus and involvement of the skin is reported. The lesions in the salivary gland and in the thymus showed the typical features of a lymphoma arising from the mucosa associated lymphoid tissue (MALT) and comprised lymphatic follicles, centrocyte-like (CCL) cells and lymphoepithelial lesions. Immunohistochemistry and Southern blot analysis supported the hypothesis that these lesions can originate from the same cellular clone. These findings confirm the occurrence of low grade B cell MALT lymphoma in the thymus and the possibility of spread of MALT lymphoma to other mucosal sites.

Evaluation of non-isotopic in situ hybridization for mRNA in reactive and neoplastic lymphoid cells

An evaluation of nonisotopic in situ hybridization (NISH) for mRNA in archival lymphoid tissue was carried out and an analysis of factors affecting the final outcome was performed. A modification of the in situ reverse transcription method for RNA preservation assessment has been used and described. We have shown that, for frozen samples mRNA detection is optimal within 3 months of the biopsy being taken, while preservation declines after 1 year of storage.

Molecular genetics and lymphoproliferative disorders

Clonality of T- and B-cell lymphoproliferative disorders can be determined by gene rearrangement studies when morphology and surface immunostaining are nondiagnostic. TcR and lg gene rearrangements have been demonstrated in many different hematologic disorders and TcR gene rearrangement has been particularly useful in the diagnosis of patients with CD8 large granular lymphocyte leukemias. TcR gene rearrangement may also be useful to distinguish Hodgkin's disease from T-cell non-Hodgkin's lymphoma. Gene rearrangement is usually performed by Southern analysis, and it is beneficial to run multiple enzyme-probe combinations to maximize the detection of clonal rearrangements. More recently, several laboratories have begun to use polymerase chain reaction (PCR) for gene rearrangement analysis. PCR offers an improved turnaround time, eliminates partial digestion artifacts, and allows for the use of paraffin embedded material. In addition to rearrangements of the TcR and lg genes, analysis of alterations in other genes such as bcl-1, bcl-2, bcl-6, and c-myc are also useful as clonal markers and aid in the classification of lymphomas.

Design of cassette baculovirus vectors for the production of therapeutic antibodies in insect cells

BACKGROUND

Various systems have been described for the expression of recombinant monoclonal antibodies for therapeutical applications. Insect cells offer great advantages with respect to post-translational modifications, stability, yields and applications.

OBJECTIVES

To construct plasmid cassette transfer vectors in order to express chimeric, humanized or human antibodies in insect cells using baculovirus expression system.

STUDY DESIGN

Two transfer vectors, pBHuC kappa and pBHuC gamma 1, were designed. They contain a viral promoter (polyhedrin or p10 promoters, respectively), a signal peptide sequence and a human immunoglobulin light chain C kappa gene or heavy chain C gamma 1 sequence, respectively. Restriction sites have been introduced to allow insertion of rearranged variable genes, after amplification by polymerase chain reaction.

RESULTS

Recombinant baculoviruses expressing complete immunoglobulins have been generated by a double-recombination event between baculovirus DNA and the loaded cassette transfer vectors.

CONCLUSION

Our genetic cassette approach makes this system a very flexible and convenient one for the rapid production of therapeutic monoclonal antibodies with heavy and light chains of any human isotype. Specific variable regions selected by the antibody phage display technology can be easily transferred in these vectors to obtain a complete antibody.

Km genotyping by polymerase chain reaction (PCR) using allele-specific amplification primers

We developed a method for identifying genetic polymorphisms of the human immunoglobulin kappa light chain, namely the Km allotypes, by allele-specific amplification by means of the polymerase chain reaction (PCR). This procedure consisted of first and second PCR. In the first PCR, the 353 bp fragment of the human immunoglobulin kappa light chain constant gene was amplified without differentiating individual alleles. In the second PCR, the specific sequence in each of the three alleles Km*1, Km*1,2 and Km*3, in the first PCR product was specifically amplified using allele-specific primers. The product of the second PCR was separated by electrophoresis on a polyacrylamide gel and the band was observed by means of UV trans-illumination after staining with ethidium bromide. From DNA extracted from lymphocytes, the specific sequence of each Km allele was selectively amplified, and the Km genotype was identified. Moreover, the Km genotype could be ascertained from whole blood, saliva and hair roots without DNA extraction. No genetic contradiction was found in the results of Km genotyping among parents and their children. The estimated gene frequency of 115 Japanese individuals living in Okayama Prefecture, Japan, was: Km*3 = 0.739 and Km*1,2 = 0.261.

Noninvasive localization of experimental atherosclerotic lesions with mouse/human chimeric Z2D3 F(ab')2 specific for the proliferating smooth muscle cells of human atheroma. Imaging with conventional and negative charge-modified antibody fragments

BACKGROUND

A murine monoclonal antibody designated Z2D3 (IgM) generated against homogenized human atherosclerotic plaques was demonstrated to be highly specific for proliferating smooth muscle cells. The primary clone subsequently was genetically engineered to provide a mouse/human chimeric antibody with human IgG1 constant region expressed in a rat myeloma cell line. The resulting Z2D3-73.30 chimeric retained the immunoreactivity relative to the parent Z2D3-IgM and was pepsin-digested to yield F(ab')2. 111In-labeled chimeric Z2D3 F(ab')2 was then used for noninvasive imaging of experimental atherosclerotic lesions. To improve the imaging characteristics, we modified chimeric Z2D3 F(ab')2 fragments to carry a high negative charge. Improved visualization of targets with 111In-labeled, negatively charged, polymer-modified antibodies most probably is the result of faster blood clearance and a decrease in nontarget background activity.

METHODS AND RESULTS

Experimental atherosclerotic lesions were induced in rabbits by deendothelialization of the infradiaphragmatic aorta followed by a 6% peanut oil-2% cholesterol diet. After 12 weeks, localization of the conventionally labeled 111In-Z2D3 F(ab')2 (24 Mbq [650 microCi]/500 to 750 micrograms) (n = 4) was compared with 111In-labeled, negatively charged, polymer-modified Z2D3 F(ab')2 (24 Mbq [650 microCi]/25 to 50 micrograms) in eight atherosclerotic rabbits. Three control rabbits also received radiolabeled polymer-modified Z2D3. Ten rabbits with atherosclerotic lesions received 111In-labeled nonspecific human IgG1 F(ab')2 with (n = 6) or without (n = 4) negative charge modification. Atherosclerotic lesions were visualized in all rabbits with the conventional Z2D3 F(ab')2 at 48 hours. However, unequivocal lesion visualization was possible at 24 hours only with negatively charged, polymer-modified Z2D3 F(ab')2. Quantitative uptake of F(ab')2 fragments was essentially determined by the presence of atherosclerotic lesions (F1.37 = 69.8; P < .0001) and the specificity of the antibody (F1.37 = 36.6; P < .0001). Uptake of the conventional Z2D3 in atherosclerotic lesions (mean +/- SEM percent injected dose per gram, 0.112 +/- 0.024%) was six times higher than background activity in the normal aortic segments (nondenuded thoracic aorta; mean percent injected dose per gram, 0.019 +/- 0.003%). Uptake of the conventional Z2D3 was also significantly higher than that of nonspecific human IgG1 F(ab')2 (0.027 +/- 0.004%). Specific uptake of the conventional Z2D3 in the lesions was comparable to the charge-modified Z2D3 uptake (0.084 +/- 0.017; P = .20). Uptake of negative charge-modified Z2D3 in the lesions was significantly higher than in the corresponding background activity in normal thoracic aorta (0.021 +/- 0.002). Uptake of negative charge-modified Z2D3 F(ab')2 in the lesions was higher than the uptake of negative charge-modified nonspecific IgG1 F(ab')2 (0.020 +/- 0.002) in the lesions. Uptake of charge-modified Z2D3 in the atherosclerotic lesions was also significantly higher than the corresponding regions of the aorta of the control rabbits (0.017 +/- 0.002; F1.18 = 27.9; P = .0001). There was, however, no difference in the specific lesion uptake of negative charge-modified Z2D3 at 24 hours (0.079 +/- 0.014) and 48 hours (0.084 +/- 0.0017; P = .99) after intravenous administration. Nontarget organ activities were lower with negative charge-modified 111In-labeled Z2D3 F(ab')2 than with the conventional Z2D3 F(ab')2. Mean kidney activity was fourfold less with the modified (0.45 +/- 0.06) than with the conventionally radiolabeled (1.67 +/- 0.264; P = .001) Z2D3 F(ab')2.

Rapid expression of an anti-human C5 chimeric Fab utilizing a vector that replicates in COS and 293 cells

Inhibition of complement system activation requires the development of soluble nonimmunogenic inhibitors with good tissue penetrating abilities that are themselves unable to activate complement. Chimeric mouse/human Fabs capable of blocking the activity of complement proteins are likely to fulfill these criteria. Several monoclonal antibodies that inhibit the activation of the human complement system have recently been developed. To examine the properties of chimeric Fab derived from these monoclonal antibodies, we have developed an expression system which allows the rapid production of milligram quantities of chimeric Fab. Both the chimeric light chain and the chimeric Fd were co-expressed from the same vector, pAPEX-3P. This vector contains the SV40 origin of replication, which allows the rapid production of chimeric Fab in COS cells for preliminary characterization. Additionally, pAPEX-3P contains the Epstein-Barr virus origin of replication and a puromycin selectable marker for maintenance as a stable episome in human cell lines. A production system consisting of transfected 293-EBNA cells cultured in serum free medium followed by protein G-Sepharose chromatography of the conditioned medium was found to be sufficient for the rapid production of purified chimeric Fab. Here we have utilized this expression system to demonstrate that an anti-human C5 chimeric Fab was a potent inhibitor of complement activation in both in vitro activation assays and an ex vivo model of complement-mediated tissue damage.

Genotype study of non-Hodgkin's lymphoma

DNA from 47 patients with non-Hodgkin's lymphoma (NHL) was studied for immunoglobulin and T-cell receptor (TCR) gene rearrangements with Southern blot hybridization. In 83% of the cases the genotypic changes were consistent with immunophenotypic and morphologic examination. Two cases showed mixed genotype and 9 cases of B-cell NHL (67% of centroblastic, 36% of follicular and 33% of large cell anaplastic) showed a population of cells with TCR gamma rearrangements in addition to immunoglobulin rearranged bands. We compared the TCR gamma variable region usage in these rearrangements in B-cell NHL with T-cell NHL and reactive hyperplasia. In T-cell NHL TCR gamma variable regions located at the 3' part of the variable locus were used more often, whilst in B-cell NHL regions of the 5' portion of the locus were preferentially used. Our results confirm the genotypic heterogeneity of histologically defined subtypes of NHL.

Nucleotide substitution type dependence of generation time effect of molecular evolution

Using DNA sequence data of 18 genes from 14 mammals, we analyzed how the average molecular evolution rate per year per site (Vy) depends on the generation time (g). (I) Assuming the relation Vy varies; is directly proportional to g(-alpha), the index of generation time effect, (alpha) was estimated to be about 0.14 for amino acid replacement substitutions (A), and about 0.32 for synonymous substitutions (S). (II) Assuming the relation Vy = V(m)g g-1 + V(e)y, where V(m)g and V(e)y are constant independent of g, the fraction, r(e) = V(e)y/Vy, of the mutation rate independent part (V(e)y) in the total evolution rate (Vy) was estimated under the assumptions of the star phylogeny and the constancy of the mutation rate per generation. r(e) was smallest for mouse with the shortest generation time among our analyzed species, and it was estimated to be about 0.57 for A and 0.31 for S. Both results do not support the view that Vy is equal to the neutral mutation rate per site both for A and for S. They are in line with the thesis that, at least for A and probably even for S, the molecular evolution rate is influenced by some causes other than the mutation rate, such as changing environment.