Demethylation of ERV3, an endogenous retrovirus regulating the Krüppel-related zinc finger gene H-plk, in several human cell lines arrested during early monocyte development

The activation of H-plk (Human-proviral linked Krüppel), a human Krüppel-related zinc finger gene in organs such as placenta, adrenal cortex, and testis, is probably due to insertion of an endogenous retrovirus, ERV3, upstream of the gene. Several differently spliced transcripts originate from this locus, e.g., a transcript encoding the retroviral envelope protein and a few differentially spliced transcripts encoding both the env and the zinc finger protein. During a screening for zinc finger proteins expressed during monocyte differentiation, two H-plk encoding cDNA clones were isolated from the human monoblast cell line U-937. Northern blot analysis of a panel of human hematopoietic cell lines showed high levels of constitutive expression of this zinc finger transcript in two monocytic cell lines (U-937 and THP-1) but not in any of the other cell lines or tissues tested. In addition, the H-plk transcript was upregulated by the phorbolester PMA in U-937 and in an additional monocytic cell line, MonoMac 6. Genomic Southern blot analysis of a panel of hematopoietic cell lines, after cleavage with the methylation sensitive enzyme Xho I, led to the detection of tissue specific demethylation in all three monocytic cell lines. The Xho I site was mapped to a position just downstream of the regulatory region of the endogenous retrovirus. By analysis of the U-937 cell line with two additional restriction enzymes, Nar I and Sma I, the demethylation was shown to affect at least three independent CpG dinucleotides in this region of the gene. In summary, the present data provide evidence for specific demethylation of this genomic region, in cells of monocytic origin, resulting in enhanced transcription of the genetic regions derived from both the env region of the retrovirus and the Krüppel-related zinc finger gene.

Cloning, structural analysis, and expression of the pig IgE epsilon chain

As a step in the evolutionary studies of immunoglobulin E (IgE) and for the purpose of developing new reagents that will facilitate a more detailed analysis of IgE-mediated inflammatory reactions in a large animal model, we here present the cloning of the epsilon chain of IgE in the domestic pig (Sus scrufa). A partial cDNA clone for the epsilon chain of pig IgE was isolated by polymerase chain reaction (PCR) amplification using degenerate primers directed against conserved regions in the second (CH2) and the fourth (CH4) constant domains of IgE. cDNA derived from mRNA isolated from the spleen and lymph nodes of a pig actively sensitized with a protein extract from the nematode Ascaris suum was used as template. Screening of a spleen cDNA library with the partial cDNA clone as probe resulted in isolation of a clone that contained the entire coding region. The nucleotide sequence was determined and was found to conform with the previously identified mammalian epsilon-chain sequences. The highest degree of similarity was found to sheep IgE. A DNA construct encoding a baculovirus signal sequence, a histidine hexapeptide, and the CH2-CH3-CH4 domains of the pig IgE epsilon chain was obtained by PCR amplification. The construct was ligated into the baculovirus expression vector pVL1392. Infection of High Five insect cells with recombinant baculovirus resulted in expression and secretion of a soluble 6 x His-CH2-CH3-CH4 protein product.

Secretory granule proteases in rat mast cells. Cloning of 10 different serine proteases and a carboxypeptidase A from various rat mast cell populations

Two of the major rat mast cell proteases, rat mast cell protease 1 (RMCP-1) and RMCP-2, have for many years served as important phenotypic markers for studies of various aspects of mast cell (MC) biology. However, except for these proteases only fragmentary information has been available on the structure and complexity of proteases expressed by different subpopulations of rat MCs. To address these questions, cDNA libraries were constructed from freshly isolated rat peritoneal MCs and from the rat mucosal MC line RBL-1. cDNA clones for 10 different serine proteases (RMCP-1-10), and the MC carboxypeptidase A were isolated and characterized. Six of these proteases have not been isolated previously. Based on their protease content, three separate subpopulations of MCs were identified. Connective tissue MCs (CTMCs) from the ear and peritoneum express the chymases RMCP-1 and -5, the tryptases RMCP-6, and -7 and the carboxypeptidase A. However, based on a large difference in the level of expression of RMCP-7, CTMCs of these two organs may be regarded as two separate subpopulations. RMCP-2 and the three closely related proteases of the RMCP-8 subfamily were identified as the major mucosal MC proteases in rat. In contrast to what has been reported for human MCs, no expression of cathepsin G or cathepsin G-like proteases was detected in any of the rat MC populations. To determine mRNA frequencies for the various proteases expressed by normal tissue MCs, an unamplified peritoneal MC cDNA library was screened with a panel of mono-specific cDNA probes. These results showed that peritoneal MCs are highly specialized effector cells with mRNA frequencies for the major proteases in the range of several percent of the total mRNA pool.

Characterization of cDNA clones encoding mouse proteinase 3 (myeloblastine) and cathepsin G

Serine proteases are the most abundant granule constituents of several major hematopoietic cell lineages. Due to their high abundance and their strict tissue specificity they have become important phenotypic cell markers used for studies of various aspects of hematopietic cell development. Using a polymerase chain reaction (PCR)-based strategy for the isolation of trypsin-related serine proteases, we were able to isolate cDNAs for two of the major neutrophil and monocyte serine proteases in the mouse, cathepsin G and mouse protease 3 (myeloblastin). The internal PCR fragments were used as probes to screen a mouse mast cell cDNA library and a cDNA library originating from a mouse monocytic cell line (WEHI-274.1). Full-length cDNAs for mouse cathepsin G and proteinase 3 were isolated and their complete sequences were determined. Northern blot analysis revealed expression of cathepsin G in immature cells of the monocyte macrophage lineage but also in the connective tissue mast cell line MTC. Proteinase 3 was expressed in several cell lines of myelo-monocytic origin and in one B-cell line, but not in any of the other cell lines tested. The isolation of cDNAs for mouse cathepsin G and mouse proteinase 3, together with the previous characterization of the gene for mouse N-elastase, and the entire or partial amino acid sequences for porcine azurocidine, equine N-elastase and proteinase 3, rat, dog, and rabbit cathepsin Gs in evolutionary relatively distantly related mammalian species, indicates that these four members of the serine protease family have been maintained for more than 100 million years of mammalian evolution. This latter finding indicates a strong evolutionary pressure to maintain specific immune functions associated with these neutrophil and monocyte proteases. All amino acid positions of major importance for the cleavage site selection have also been fully conserved between mouse and human proteinase 3 and a few minor changes have occurred between mouse and human cathepsin G.

Characterization of a human basophil-like cell line (LAMA-84)

LAMA-84, a human leucocytic cell line, which upon establishment was described as having megakaryocytic, erythroid and granulocytic characteristics, was analysed for expression of various differentiation markers. In addition to some of the previously described phenotypic characteristics, this cell line was found to express mRNA for several proteins characteristic for basophilic leucocytes and mast cells. The authors show that LAMA-84 cells express mRNA for the mast cell tryptase, the proteoglycan core protein, carboxypeptidase A and the alpha and beta chains of the high affinity IgE receptor (Fc epsilon RI). The authors examined the potential of LAMA-84 to differentiate in serum-free medium or after DMSO or PMA treatment. Depending on the inducing factor, surface expression of the Fc epsilon RI alpha-chain was increased from 20% to 35-50% of the cells and mRNA levels for tryptase were increased in serum-free medium and after DMSO treatment. LAMA-84 was found to express CD13, CDw17, CD29, CD33, CD40, CD45 and CD117. Furthermore, mRNA for the eosinophil/basophil markers Charcot-Leyden crystal (CLC) protein and the major basic protein (MBP), as well as the erythrocyte differentiation marker alpha-globin, was detected. However, the authors observed only trace amounts of mRNA for another erythroid differentiation marker (glycophorin), trace amounts of the megakaryocytic marker GPIIIa, and no detectable level of GPIb alpha. By comparing the expression pattern of a panel of differentiation markers in LAMA-84, and a second human cell line (KU812) expressing a basophil phenotype, it is evident that these cell lines, which presently are the only two cell lines identified with basophilic characteristics, share a large number of phenotypic characteristics.

Stem cell factor-dependent human cord blood derived mast cells express alpha- and beta-tryptase, heparin and chondroitin sulphate

The present study sought to determine the expression of alpha- and beta-tryptase in in vitro differentiated human cord blood derived mast cells. We also analysed the glycosaminoglycan composition and the phenotype of the cells. The major protease in human mast cells is tryptase, and cDNAs for two different human tryptases have been characterized, the so-called alpha- and beta-tryptase. By reverse transcriptase-polymerase chain reaction (RT-PCR) we could show that stem cell factor (SCF)-dependent cord blood derived mast cells express both alpha- and beta-tryptase. Furthermore, the cells were stained with a monoclonal antibody (mAb) against tryptase, and the tryptase was enzymatically active cleaving the substrate Z-Gly-Pro-Arg- methoxy-2- naphthylamide (MNA). The majority of the cord blood derived mast cells could also be stained with mAbs against chymase, cathepsin G and CD68. They also expressed Kit/SCFR (CD117), CD13, CD29 and CD45 on the cell surface. The proteoglycan-derived polysaccharide composition of the cells was estimated to be 25-35% of heparin origin and 65-75% of chondroitin sulphate origin. Hence, the cord blood derived mast cells exhibit a phenotype in common with the so-called MCTC type of human mast cells.

Is vaccination against IgE possible?

A substantial reduction in the levels of both total and antigen specific IgE will most likely result in improved symptom scores in atopic individuals. Based on this assumption we initiated a project to study the possibility of reducing levels of circulating and mast cell bound IgE, by inducing a strong autoimmune antibody response against IgE in the host. Bacterially produced fusion proteins containing constant domains two (CH2) and three (CH3) of rat IgE directly linked to the glutathione-S-transferase (GST) protein from Schistosoma japonicum or to the maltose binding protein of Esherichia coli were used as the active components of the allergy vaccine. Injection of either of these fusion proteins together with adjuvant led to the induction of a strong autoimmune anti-IgE response in several IgE low or medium responder strains of rats. Vaccination of ovalbumin sensitised Wistar rats with the GST-C2C3 fusion protein resulted in a profound decrease in serum IgE levels and later in a nearly complete block in histamine release from mast cells and basophils upon challenge with either a cross-linking polyclonal anti-IgE antiserum or a specific allergen. This shows that it is possible to reduce IgE levels in an animal to such an extent that it gives a clear clinical effect. Recent studies with an extended panel of rat strains including four IgE high responder strains, indicate that induction of the autoimmune response is dependent on the plasma concentration of IgE before vaccination. A high concentration of IgE has a negative effect on the induction of autoimmunity, most likely by inducing a B-cell tolerance in the host. Vaccinated subjects with very high IgE concentrations thereby responds poorly to the vaccine. Current studies are aimed at overcoming this potential limitation of the vaccination procedure.

A single major transcript encodes the membrane-bound form of rat immunoglobulin E

The primary structure of the membrane-bound form of rat immunoglobulin E was determined by PCR amplification and nucleotide sequence analysis of its mRNA. The sequence was found to correspond to the previously identified membrane exons of the rat epsilon chain gene. The donor splice site in the C4 exon was mapped to a position 35 nt upstream of the stop codon for the secreted form of rat IgE. Therefore, the membrane-bound IgE lacks the 12 C-terminal amino acids present in the secreted form of the protein. Recently, five novel epsilon chain transcripts were isolated from human IgE producing B-cells or B-cell lines. Four of these transcripts encode proteins which differ in their C-terminal ends from the classical membrane or secreted forms of human IgE. To investigate if these transcripts were likely to represent functional mRNAs, their evolutionary conservation was studied by screening a rat IgE producing B-cell line for the expression of similar transcripts. By PCR amplification and cloning of transcripts, containing both the C3 and the M2 exons, approximately 10,000 independent cDNA clones were obtained. These clones were screened with probes directed against regions specific for each of the five novel human epsilon chain mRNAs. However, no evidence was found for the presence of transcripts with a similar structure, indicating that no specific function associated with these transcripts and their corresponding proteins has been conserved between human and rat. The lack of additional M2-containing transcripts in the rat suggest that the novel human IgE transcripts are byproducts of differential splicing and that they most likely encode proteins with no evolutionarily important function.

Isolation of cDNA clones for 42 different Krüppel-related zinc finger proteins expressed in the human monoblast cell line U-937

To study the complexity and structural characteristics of zinc finger proteins expressed during human hematopoiesis and to isolate novel regulators of blood cell development, a degenerate oligonucleotide probe specific for a consensus zinc finger peptide domain was used to isolate 63 cDNA clones for Krüppel-related zinc finger genes from the human monoblast cell line U-937. By extensive nucleotide sequence and Northern blot analysis, these cDNA clones were found to originate from approximately 42 different genes (HZF 1-42) of which only 8 have previously been described. Northern blot analysis showed that a majority of these genes were expressed at comparable levels in U-937 and HeLa cells. The large number of individual genes represented among the 63 clones and their apparent non-cell-type-specific expression suggest that the majority of the Krüppel-related zinc finger genes are likely to be expressed in most human tissues. In contrast, some of the genes displayed a restricted expression pattern, indicating that they represent potential regulators of monocyte differentiation or proliferation. Detailed structural analysis of the first 12 cDNAs (HZF 1-10) and a partial characterization of HZF 11-42 revealed that a common feature of human Krüppel-related zinc finger proteins is the presence of tandem arrays of zinc fingers ranging in number from 3 to over 20 that are preferentially located in the carboxy-terminal regions of the proteins. In addition, several novel KRAB-containing zinc finger genes and a novel conserved sequence element were identified.

Genes for mast-cell serine protease and their molecular evolution

Trypsin-related serine proteases are encoded by a very large gene family in mammals. We describe here a comparative analysis of the genomic DNA sequences of mouse, rat, and human mast-cell-specific serine protease genes. Strong evidence was found for multiple exchanges of genetic information between closely related members of this gene family. The 5' regulatory regions of MMCP-1 and MMCP-L share a remarkably high degree of sequence identity (98%), starting 10 base pairs downstream of exon 1 and extending to the end of the presently sequenced region at position -1347 of the MMCP-1 gene. The remaining parts of the two genes share approximately 80% sequence identity. Evidence for at least two additional, but not so recent, exchanges was found in the 3' regions of the MMCP-4 and MMCP-L genes and in the 5' regions of the genes for MMCP-1 and MMCP-2. The 5' regulatory regions of all presently characterized mouse mast-cell-specific chymotrypsin-like serine protease genes exhibit over 88% sequence identity in the region from the transcription initiation site to approximately position -600. An exception is MMCP-5 which is the most distantly related member of this subfamily. The high degree of sequence similarities indicates a strong evolutionary homogenization of the 5' regulatory region, possibly by several gene conversion events. In addition, several insertions of genetic information have been identified in genes for mast-cell chymases and genes for T-cell granzymes. A number of these have been found to represent repetitive sequences, such as L1. The previously characterized tissue-specific enhancer element of the RMCP II gene was identified as a member of a middle repetitive sequence. A cDNA for a newly discovered pseudogene, closely related to the mouse mast cell chymases was isolated by polymerase chain reaction amplification from a mouse connective tissue-like mast cell line. The structure of this cDNA is presented. We also present the characterization of a novel spliced variant of MMCP-6 that contains an alternative 3' terminal exon (exon 6). The function of this variant, if any, is still unknown. A comparative analysis of amino acid sequence identities between different hematopoietic serine proteases shows that a high degree of sequence similarity does not always correlate with relateness in cleavage specificity. This indicates that the substrate specificity evolved with a higher evolutionary rate than the degree of overall amino acid sequence identity of these proteases.

Human cell lines U-937, THP-1 and Mono Mac 6 represent relatively immature cells of the monocyte-macrophage cell lineage

Three human monocytic cell lines, U-937, THP-1 and Mono Mac 6 have, because of their morphology and staining properties, been classed as cell lines frozen in a window of the monocyte differentiation lineage corresponding to monoblasts and/or immature monocytes. These cell lines were analyzed for expression of a panel of hematopoietic differentiation markers by Northern blot analysis. They were all found to express one or several biochemical markers characteristic of immature cells in monocytic development, including myeloperoxidase, N-elastase, cathepsin G, myeloblastin, and azurocidin. Normal peripheral blood monocytes did not express these markers. Moreover, several markers expressed at high levels in mature monocytes, such as lysozyme, CD14, MHC class II and alpha-1 antitrypsin were either not expressed or were expressed only at low levels in the three cell lines analyzed. These results show that arrested differentiation at a relatively early stage of monoblast development is a common denominator for these human monocytic cell lines. Thus, transforming mutations acting at such an immature differentiation stage may frequently lead to neoplastic transformation, whereas similar mutations occurring at a more mature differentiation stage never give rise to any leukemias due to the loss of proliferative potential in committed cells.

Phenotypic characterization of the human mast-cell line HMC-1

The cell line HMC-1, derived from a patient with mast cell leukaemia, is the only established cell line exhibiting a phenotype similar to that of human mast cells. This paper reports on a detailed characterization of the expression of a panel of markers for various types of immature and mature haematopoietic cells in the HMC-1. We also studied the potential of HMC-1 to differentiate upon treatment with conditioned media from the human T-cell line Mo, retinoic acid or DMSO. HMC-1 was found to express several mast cell-related markers. A high expression of Kit, the receptor for stem-cell factor, was detected. The majority of the cells were stained with a MoAb against the mast cell-specific serine protease tryptase. Of particular interest was the finding that beta-tryptase mRNA, but not alpha-tryptase mRNA, was expressed in HMC-1. Using enzyme-histochemistry we were able to show that the beta-tryptase was enzymatically active, indicating that tryptase can form active homotetramers. Both heparin and chondroitin sulfate were found to be present in approximately equal amounts. HMC-1 lacked surface expression of the high-affinity IgE receptor, which was confirmed by the absence of mRNA of the alpha- and beta-chains of the IgE-receptor complex. However, a strong expression of the gamma-chain of the IgE-receptor complex was detected. A positive staining of the monocyte/macrophage marker CD68 was obtained, as well as a strong hybridization signal for the eosinophilic/basophilic-related differentiation marker the Charcot-Leyden crystal. Treatment of HMC-1 with conditioned media from the human T-cell line Mo, retinoic acid or DMSO induced only moderate changes in the surface or intracellular expression of the studied markers. The agents tested neither induced any of the monocyte/granulocyte markers examined, nor expression of the Fc epsilon RI alpha-chain.

Profound reduction in allergen sensitivity following treatment with a novel allergy vaccine

A novel approach is described for the treatment of IgE-mediated allergic reactions which is based on the induction of a strong anti-IgE response in the host. Vaccination of ovalbumin-sensitized rats with constant domains two and three of rat IgE coupled to a heterologous carrier protein resulted in a profound decrease in serum levels of IgE, and later in a nearly complete block of histamine release from mast cells and basophils upon challenge with either a cross-linking polyclonal anti-IgE antiserum or a specific allergen.

Expression of a mast cell tryptase in the human monocytic cell lines U-937 and Mono Mac 6

Expression of a mast cell tryptase mRNA was detected in two human monocytic cell lines, the U-937 and the Mono Mac 6, and in normal human peripheral blood (PB) monocytes. In the U-937 cell line but not in normal PB monocytes, the tryptase expression was upregulated 3-50 fold following phorbol ester (PMA)-induced differentiation, but no such induction was seen after retinoic acid, interferon-gamma or vitamin D3 exposure. The tryptases expressed in PMA-induced and non-induced U-937 and in Mono Mac 6 were characterized by PCR amplification and nucleotide sequence analysis. The U-937 cell line was found to express a tryptase identical to one of the previously cloned mast-cell beta tryptases (Tryptase I), and the tryptase expressed in Mono Mac 6 was found to be nearly identical to the previously cloned alpha tryptase. By northern blot analysis with oligonucleotide probes specific for the alpha and beta tryptases both cell lines were found to express only one type of tryptase. Densitometric quantifications of tryptase mRNA levels, in the two cell lines, showed approximately 80 times higher mRNA levels in Mono Mac 6 compared to non-induced U-937. Immunohistochemical staining for tryptase showed a marked heterogeneity in the Mono Mac 6 cell line. Only one out of 10 cells were positive for the protein but the levels in these cells were very high, equivalent, or even higher than the levels seen in the human mast cell line HMC-1. This shows that the expression of a single tryptase, in this case the alpha tryptase, is sufficient for the production of a stable protein and probably also a stable proteolytically active tetramer. The family of human mast-cell tryptases has been considered to represent a class of proteases specifically expressed in mast cells and basophilic leucocytes. The expression of tryptases in two monocytic cell lines and in normal PB monocytes indicate that in humans, the lineage specificity of these serine proteases is less restricted than earlier expected. The cloning of a full length cDNA for the murine counterpart to the human mast cell tryptases, the MMCP-6, is presented. No expression of the MMCP-6 was detected in a panel of mouse monocyte or macrophage cell lines indicating a species difference in the lineage specificity of the 'mast cell tryptases'.

Characterization of a tryptase mRNA expressed in the human basophil cell line KU812

The expression of a tryptic serine protease was detected in the cell line KU812 by Northern blot analysis with an oligonucleotide probe directed against a conserved region present in all of the five presently cloned human mast cell tryptases. PCR primers designed for the amplification of a nearly full-length copy of tryptase mRNAs were used to study the identity of the KU812 tryptase. Ten clones were characterized and all were found to be identical to one of the tryptases previously cloned from a human skin cDNA library. This tryptase has been thought to originate from mast cells of the skin. Two possible explanations may account for the observed identity between the presumed mast cell tryptase and the KU812 tryptase. Firstly, it is possible that the KU812 tryptase is a basophil-specific tryptase which has previously been cloned from a human skin cDNA library containing low levels of cDNA copies derived from basophils in the starting material. Secondly, the KU812 cell line, and possibly normal basophils, express a tryptase which is identical to one of the tryptases expressed in normal skin mast cells. We cannot at present rule out any of the two possibilities, but we favour the second explanation as being the most likely.

Constitutive and inducible expression of PDGF in the human basophilic cell line, KU 812

The human basophilic cell line KU 812, that also has some mast cell characteristics, was found to express the PDGF-A gene and secrete PDGF-A like activity. After treatment with IL-6+ TNF-alpha, the PDGF-A mRNA expression increased as did cytoplasmic immunostaining with anti-PDGF antibodies. Secretion of PDGF-A was visualized by immunoprecipitation. An augmentation of non-secreted PDGF-like activity after IL-6+ TNF-alpha treatment was not accompanied by induction of the long splice variant of the PDGF-A-chain mRNA. Treatment with TPA caused an increase in PDGF-A expression and in addition, an induction of PDGF-B transcripts were seen. Staining of cytospin preparations with anti-PDGF antibodies visualized a substantial increase in immunostaining of the TPA treated cells and both intracellular and secreted PDGF-AA-like activity was substantially increased as compared to untreated control cultures. There was a concomitant induction of exon 6 specific mRNA, corresponding to a cellular retention signal after TPA treatment. Our results show that PDGF can be produced by a cell line of the basophilic/mast cell lineage, i.e. cells involved in allergic disorders and inflammation.

Characterization of four novel epsilon chain mRNA and a comparative analysis of genes for immunoglobulin E in rodents and man

The nucleotide sequence of the 3' region of the epsilon chain gene for human IgE is presented. A comparison of the entire region from 5' of exon C1 to the M2 exon of the mouse, rat and human epsilon chain genes shows that the overall structure of the epsilon chain gene have changed only minimally during the 60-70 million years of evolutionary separation between rodents and man. We have previously shown that a number of rearrangements larger than 10 bp have relatively recently occurred in the C4/M1 intron of the rat or the mouse epsilon chain genes. A majority of these rearrangements were found within or in close proximity to repetitive sequences of Z-DNA-forming potential (CA dinucleotide repeats). The C4/M1 intron has evolved very rapidly, to such an extent that no apparent homology can be detected between rodents and man. Only remnants of the repetitive sequences are present in man, supporting the theory that repetitive sequences having Z-DNA-forming properties may play a role in the evolution of the eucaryote genome by promoting recombinations, leading to a rapid evolutionary drift of sequences in close proximity to these repeats. We report here the characterization of the membrane domains of human IgE and four novel mRNA transcribed from the human epsilon chain locus. The primary structures have been determined by polymerase chain reaction cloning and nucleotide sequence analysis. All five mRNA contain the C3 domain and the membrane exon 2 (M2). Due to frame shifts caused by novel splice sites or novel splice-site combinations, the proteins encoded by three out of these four novel mRNA differ in their carboxy-terminal end from the classical secreted or membrane-bound immunoglobulins. Northern blot analysis shows significant levels of at least three out of these four novel mRNA in an IgE-producing human cell line. One of the mRNA encodes a transmembrane-like structure which has characters in common with the transmembrane region of the CD3 components of the T cell receptor complex (CD3 gamma, delta and epsilon). This indicates that IgE-producing B cells possibly have two separate signal-transducing systems. A comparison of the classical membrane anchoring domain of the human & chain with a panel of immunoglobulin membrane domains from fish to higher mammals is presented. A tyrosine and a glutamine residue is found to be conserved between all cytoplasmic domains of all post-switch immunoglobulin classes indicating a functional conservation of these amino acid residues.(ABSTRACT TRUNCATED AT 400 WORDS)

Phenotypic characterization of KU812, a cell line identified as an immature human basophilic leukocyte

The knowledge about the differentiation of basophilic leukocytes is fragmentary. This report discusses a detailed phenotypic characterization of molecular markers for hematopoietic differentiation in a basophilic leukemia cell line, KU812. The expression of markers for lymphoid, erythroid, neutrophil, eosinophil, monocytic, megakaryocytic, mast cell and basophil differentiation was analyzed at the mRNA level by Northern blots in the KU812 cells, and for reference, in a panel of human cell lines representative of the different hematopoietic differentiation lineages. KU812 was found to express a number of mast cell and basophil-related proteins, i.e. mast cell tryptase, mast cell carboxypeptidase A, high-affinity immunoglobulin (IgE) receptor alpha and gamma chains and the core protein for heparin and chondroitin sulphate synthesis. We found no expression of a number of monocyte/-macrophage or neutrophil leukocyte markers except for lysozyme. From earlier studies, it has been shown that lysozyme is not expressed in murine mucosal mast cell lines. This finding, together with the expression of the mast cell carboxypeptidase in KU812 might distinguish the phenotype of this cell line from that typical of mucosal mast cell lines in rodents. We found a low level of expression of the eosinophil and basophil marker, major basic protein, which might indicate a relationship between basophils and eosinophils. No expression is, however, detected with the eosinophil-specific markers eosinophil cationic protein, eosinophil-derived neurotoxin or eosinophil peroxidase. We also report an extensive screening for inducers of basophilic differentiation of the KU812 cells. The most efficient protocol of induction included serum starvation which led to a dramatic increase in a number of markers specific for mast cells and basophils such as tryptase, carboxypeptidase A and the heparin core protein. Finally, diisopropylfluorophosphate analysis of total protein extracts from KU812 show four labeled protein bands with sodium dodecyl sulfate-polyacrylamide gel electrophoresis, indicating that this cell line expresses at least three previously undescribed serine proteases of which one or more could be a potential basophil-specific marker(s).

Disseminated candidiasis due to amphotericin B-resistant Candida albicans

Although development of resistance in Candida albicans to amphotericin B is considered rare, C. albicans was persistently recovered from a 28-year-old man after a prolonged course of broad-spectrum antimicrobial therapy for a pancreatic abscess. Determination of the MICs of drugs for C. albicans in Sabouraud broth revealed MICs of 2.5 mg/l amphotericin B, greater than 40 mg/l ketoconazole, 2.5 mg/l miconazole, and greater than 40 mg/l 5-fluorocytosine. Synergy testing revealed a MIC of 0.3 mg/l amphotericin B in the presence of 2.5 mg/l 5-fluorocytosine. When intravenous 5-fluorocytosine was added to the patient's antifungal regimen, achieving levels of 125 mg/l, negative blood cultures resulted for the first time. This suggests there may be a clinical use for in vitro synergy testing as an adjunct to guide antifungal therapy for fungemia due to amphotericin B-resistant C. albicans.

Enhancement of IgE synthesis in the human myeloma cell line U-266 with an IgE binding factor from a human T-cell line

An IgE-binding factor(s) (IgE-BF(s] was partially purified from the supernatant of human HTLV-II carrying T-cell line MO. This IgE-BF(s) was shown to increase the IgE synthesis in the human myeloma cell line U-266, but did not affect its viability or growth. The effect of the IgE-BF(s) was dose-dependent and selective for IgE protein synthesis as beta 2-microglobulin synthesis in the U-266 and the immunoglobulin production in the U-1958 IgG-secreting human myeloma cell line were unaffected. The IgE-BF(s) increased the production of the epsilon heavy chain but not the lambda light chain production. The IgE-BF(s) was distinct from IL-1 beta, IL-3, IL-4, IL-5, IL-6, TNF-alpha, IFN-alpha, -beta, -gamma, M-CSF, and fragments of CD23.

Cloning and structural analysis of MMCP-1, MMCP-4 and MMCP-5, three mouse mast cell-specific serine proteases

Here we present the cloning of three novel mouse mast cell-specific serine proteases, MMCP-1, MMCP-4 and MMCP-5. A region of approximately 4 kb covering the five exons and 930 bp 5' and 280 bp 3' flanking sequences of the gene for MMCP-1 was characterized by nucleotide sequence analysis. A comparison with the corresponding region of the rat mucosal mast cell-specific protease RMCP-II is presented. cDNA clones for the mast cell proteases MMCP-4 (950 bp) and MMCP-5 (1098 bp) were isolated from a cDNA library of a connective tissue mast cell-like mouse mastocytoma cell line. All three proteases were found to belong to the family of chymotrypic serine proteases as deduced from the absence of the Asp 189 which is characteristic for all serine proteases having cleavage specificities similar to pancreatic trypsin. The active polypeptides, excluding possible post-translational glycosylations, have an Mr of 25-26 kDa. Analysis of the amino acid composition reveals a positive net charge for all three proteases MMCP-1 +3, MMCP-4 +18 and MMCP-5 +12). Based on their high sequence identity (88%) and high positive net charges (+18 and +18, respectively) we assume that the MMCP-4 is the mouse homolog to rat RMCP-I. Probes specific for each of these three highly homologous protease genes have been generated by subcloning of fragments of approximately 100 bp in length, originating from the 3' ends of the mRNA into plasmid vectors. Northern blot analysis of mRNA from a number of murine cell lines shows gene expression of these proteases to be specific for the differentiation stage of the mast cell. The MMCP-1 is expressed only at the mucosal mast cell stage and 5 only in mast cells of the connective tissue mast cell stage. These serine proteases may serve as highly specific markers in the analysis of mast cell heterogeneity, differentiation and function.

Cloning and structural analysis of a gene encoding a mouse mastocytoma proteoglycan core protein; analysis of its evolutionary relation to three cross hybridizing regions in the mouse genome

Serglycin (SGC) is a Ser-Gly-repeat-containing protein, used as a proteoglycan core protein in the parietal yolk sac and in mast cells, where glycosaminoglycan side chains are attached to the serine residues of the repeat region. In this article, the structure of the gene SGC encoding mouse SGC is reported. The gene is divided into three exons, which are all contained within a region of approximately 13 kb. Nucleotide (nt) sequence analysis was carried out on a region of 1.2 kb upstream from the first exon. The region containing the two promoters (active in parietal yolk sac and in mast cells, respectively) was analyzed for the presence of recognition sites for known DNA-binding proteins. A number of sequences closely related to known recognition sites were found in both promoters, and one consensus octamer-binding site could be identified in the putative yolk-sac promoter. Multiple regions in the mouse genome hybridizing with DNA fragments covering the Ser-Gly repeat region have previously been described, and it has been suggested that these loci may represent other proteoglycan core proteins. Analysis of nt sequence was carried out on three out of the more than 15 of these regions present in the mouse genome. However, none of the clones analyzed was found to have any open reading frame in the region of cross-hybridization which possibly could code for a SGC protein. Instead, one of the clones was found to contain an exon encoding a highly basic protein, unrelated to SGC. Hence, no evidence was found for a multigene family of Ser-Gly-repeat-containing proteoglycan-encoding genes.

Sodium-24 studies in postmastectomy lymphedema

Seven patients were studied with 24Na to determine the relative disappearance time of the isotope from the postmastectomy lymphedematous arm as compared to the normal side. The results tend to confirm previously held convictions that the edema is usually confined to the subcutaneous fat and skin. The disappearance time (T1/2) of the radioactive sodium from the muscle of the edematous side was usually comparable to that of the control side. The data also indicate that the impairment of fluid drainage from other areas, such as the lateral chest wall, that normally drain into the axilla, is impaired similarly to that of the subcutaneous fat of the arm. Operative procedures designed to relieve the edema of the arm by providing an alternate route of drainage should provide a conduit for the fluid to an area that does not normally drain to the axilla of the affected side.

Secretion of coagulant factor VIII activity and antigen by in vitro cultivated rat liver sinusoidal endothelial cells

Different types of liver cells and a few extrahepatic cell types were analysed for the presence and production of factor VIII activity (VIII:C). Only freshly prepared suspensions of rat liver sinusoidal cells and pure monolayer cultures of rat liver endothelial cells (LEC) were found to contain and secrete detectable amounts of the coagulation factor. Secretion of VIII:C by cultured LEC was inhibited by cycloheximide and by monensin. Constant levels of VIII:C were produced for at least 48 h suggesting continuous synthesis rather than a burst release of stored material. VIII:C, as measured spectro-photometrically by conversion of X to Xa, was inhibited by anti-human VIII:C antiserum. Indirect immunocytochemistry using this antiserum gave positive staining only with LEC. Immunoprecipitation of metabolically labelled proteins in conditioned rat LEC medium with the anti human VIII:C antiserum revealed the presence of proteins of similar sizes to those reported for human VIII:C. These results indicate that rat LEC are an important site for production and secretion of procoagulant factor VIII and are not only a site for storage and release of the factor. The established conditions for synthesis of VIII:C in in vitro cultivated rat LEC should provide the means to study the regulation of VIII:C synthesis.