Estradiol metabolism in cirrhosis

Abnormal estrogen metabolism has been found in cirrhosis after administration of intravenous tracers of estradiol-(3)H to 6 patients and 23 healthy controls. The major abnormalities observed involved estrogen metabolites other than the 3 "classic" ones, i.e., estrone (E1), estradiol (E2), and estriol (E3). Urinary recovery of radioactivity was regularly elevated in the patients, to an average of 71% of the dose compared to 51% in normals. This is considered to reflect the component of intrahepatic cholestasis in cirrhosis. The per cent dose recovered as urinary glucosiduronates (42%) was normal in cirrhotics in contrast to impaired glucuronidation of cortisol metabolites in this disease. E1 and E2 were present in normal amounts, and E3 was slightly elevated to 21% of the extract compared to 14% in controls. There were strikingly decreased excretion of 2-hydroxyestrone (3% compared with normal 20%) and 2-methoxyestrone (2% compared with 5%) and increased excretion of 16alpha-hydroxyestrone (12% compared with normal 6%). Thus cirrhosis, too, is characterized by the reciprocal relationship between decreased 2-hydroxylation and increased 16alpha-hydroxylation previously described in hypothyroidism and male breast cancer. However, unlike these latter, the increase of 16alpha-hydroxy metabolites was less than the decrease of 2-hydroxy metabolites. The data indicate clearcut impairment of 2-hydroxylation, suggestive impairment of 16alpha-hydroxylation, and a definite depression of the reaction 16alpha-hydroxyestrone-->estriol, the latter finding so far unique to cirrhosis. Demonstration of abnormal peripheral metabolism of estrogen in cirrhosis provides a new approach to the origin of the hyperestrogenic syndrome in this disease.

Cloning and structural analysis of two highly divergent IgA isotypes, IgA1 and IgA2 from the duck billed platypus, Ornithorhynchus anatinus

To trace the emergence of modern IgA isotypes during vertebrate evolution we have studied the immunoglobulin repertoire of a model monotreme, the platypus. Two highly divergent IgA-like isotypes (IgA1 and IgA2) were identified and their primary structures were determined from full-length cDNAs. A comparative analysis of the amino acid sequences for IgA from various animal species showed that the two platypus IgA isotypes form a branch clearly separated from their eutherian (placental) counterparts. However, they still conform to the general structure of eutherian IgA, with a hinge region and three constant domains. This indicates that the deletion of the second domain and the formation of a hinge region in IgA did occur very early during mammalian evolution, more than 166 million years ago. The two IgA isotypes in platypus differ in primary structure and appear to have arisen from a very early gene duplication, possibly preceding the metatherian eutherian split. Interestingly, one of these isotypes, IgA1, appears to be expressed in only the platypus, but is present in the echidna based on Southern blot analysis. The platypus may require a more effective mucosal immunity, with two highly divergent IgA forms, than the terrestrial echidna, due to its lifestyle, where it is exposed to pathogens both on land and in the water.

Isolation of transcriptionally active umbilical cord blood-derived basophils expressing Fc epsilon RI, HLA-DR and CD203c

BACKGROUND

Basophils are inflammatory cells associated with allergy and parasite infections. Investigation of their true biological function has long been hampered by the difficulty in obtaining sufficient amounts of pure basophils and by the lack of phenotypic markers. Moreover, it has been very difficult to clone and identify basophil-specific granule proteins, partially because of an almost complete lack of mRNA in mature circulating basophils.

METHODS

To obtain transcriptionally active immature basophils, umbilical cord blood cells were cultured in the presence of interleukin (IL)-3. The cells were analysed by flow cytometry and by histological staining.

RESULTS

The continuous presence of IL-3 in cord blood cultures resulted in the expansion of basophil precursors co-expressing FcepsilonRI and the recently described mast cell/basophil marker, 97A6 (CD203c). Several nonbasophil markers (i.e. CD3, CD14, CD15, CD16, CD19 and CD21) were absent on the cultured basophils. However, we show that in early cultures, almost 60% of the CD203c+ cells co-express human leukocyte antigen (HLA)-DR, a marker that is absent on mature circulating basophils. The presence of HLA-DR on basophil precursors may explain the low recovery (24+/-5.2%) obtained after isolation of cultured basophils, when using a conventional basophil isolation kit that removes HLA-DR+ cells. A novel purification method was developed, including a two-step cocktail of antibodies against selected markers, which resulted in both high purity (95+/-0.5%) and recovery (59+/-1.5%) of cultured basophils.

CONCLUSIONS

We here establish cord blood cultures as a source from which transcriptionally active basophil precursors can be isolated in reasonable quantities for thorough biochemical characterization.

Platypus immunoglobulin M and the divergence of the two extant monotreme lineages

A full-length cDNA clone encoding the platypus (Ornithorynchus anatinus) immunoglobulin M (IgM) heavy chain was isolated from a spleen cDNA library using a short-beaked echidna (Tachyglossus aculeatus) IgM constant region (Cµ) probe. The isolation of platypus IgM shows that O. anatinus, like all other examined jawed vertebrates, express a classical IgM molecule. Amino acid sequence comparisons of the constant regions of IgM reveals a high level sequence conservation between O. anatinus and T. aculeatus sequences (87%), and only approximately 48% identity between O. anatinus and therian Cµ sequences. The variable region of this clone belongs to clan 3, supporting the view that this family is used preferentially, if not exclusively by O. anatinus, as opposed to the use of all three variable region clans by T. aculeatus. Phylogenetic analysis of Cµ sequences supports the traditional Theria hypothesis and suggests that the O. anatinus and T. aculeatus lineages separated from their last common ancestor approximately 21 million years ago.

Mice lacking histidine decarboxylase exhibit abnormal mast cells

Histidine decarboxylase (HDC) synthesizes histamine from histidine in mammals. To evaluate the role of histamine, we generated HDC-deficient mice using a gene targeting method. The mice showed a histamine deficiency and lacked histamine-synthesizing activity from histidine. These HDC-deficient mice are viable and fertile but exhibit a decrease in the numbers of mast cells while the remaining mast cells show an altered morphology and reduced granular content. The amounts of mast cell granular proteases were tremendously reduced. The HDC-deficient mice provide a unique and promising model for studying the role of histamine in a broad range of normal and disease processes.

Molecular cloning and preliminary functional analysis of two novel human KRAB zinc finger proteins, HKr18 and HKr19

cDNA clones encoding two novel human KRAB zinc finger proteins, HKr18 and HKr19, were isolated from a human testis cDNA library. Their corresponding genes were later identified in sequences originating from chromosomes 19 and 7, respectively. On the basis of the collected information from gene and cDNA sequences, Hkr18 was found to be a protein of 94 kDa with 20 zinc finger motifs in its C terminus. The HKr19 is a smaller protein, with a molecular weight of 56 kDa containing 11 zinc finger motifs. Both HKr18 and HKr19 contained a KRAB A as well as a KRAB B domain in their N termini. Northern blot analysis showed expression of HKr18 in all human tissues tested, indicating a ubiquitous expression pattern. In contrast, HKr19 showed a more restricted tissue distribution, with detectable expression primarily in testis and fetal tissues. The HKr19 protein is a member of the large ZNF91 subfamily of KRAB zinc finger genes. A PCR-based analysis of the expression of HKr19 and other closely related genes showed that lymphoid, myeloid, and nonhematopoietic cells expressed different sets of these genes. This latter finding indicates that some members of the ZNF91 family may be involved in regulating lineage commitment during hematopoietic development. Transfection of various parts of HKr19 into human embryonic kidney cells (HEK 293 cells) showed that the entire protein and its zinc finger region were toxic to these cells when expressed at high levels. In contrast, the KRAB domain and the linker region seemed to be well tolerated.

Characterization of the gene encoding mouse mast cell protease 8 (mMCP-8), and a comparative analysis of hematopoietic serine protease genes

Serine proteases are important granule constituents in several of the major hematopoietic cell lineages. We present here the nucleotide sequence of the gene encoding mouse mast cell protease 8 (mMCP-8). mMCP-8 was initially isolated as a cDNA from a mouse mast cell line, but has recently been found to be expressed primarily by mouse basophils. mMCP-8 and its rat homologues, rMCP-8, -9, and -10, form a new group of mast cell/basophil proteases, which are more closely related to the T-cell granzymes and neutrophil cathepsin G than to the mast cell tryptases and chymases. A dot matrix comparison of the mMCP-8 gene with other closely related hematopoietic serine protease genes shows detectable homology only in the exonic regions of the genes. No indication for conservation in the promoter region or introns was observed. This latter finding indicates that the upstream regulatory region has evolved at a relatively high rate. However, despite the low degree of direct sequence conservation, no major differences in the sizes of introns or exons were observed between mMCP-8 and genes for the closest related hematopoietic serine proteases, the mouse T-cell granzymes and cathepsin G, indicating that after evolutionary separation from the T-cell granzymes and cathepsin G, the majority of mutations primarily involved single base pair substitutions or short insertions or deletions.

Conserved interaction between distinct Kruppel-associated box domains and the transcriptional intermediary factor 1

The Krüppel-associated box (KRAB) domain, originally identified as a 75-aa sequence present in numerous Krüppel-type zinc-finger proteins, is a potent DNA-binding-dependent transcriptional repression domain that is believed to function through interaction with the transcriptional intermediary factor 1 (TIF1) beta. On the basis of sequence comparison and phylogenetic analysis, we have recently defined three distinct subfamilies of KRAB domains. In the present study, individual members of each subfamily were tested for transcriptional repression and interaction with TIF1 beta and two other closely related family members (TIF1 alpha and TIF1 gamma). All KRAB variants were shown, (i) to repress transcription when targeted to DNA through fusion to a heterologous DNA-binding domain in mammalian cells, and (ii) to interact specifically with TIF1 beta, but not with TIF1 alpha or TIF1 gamma. Taken together, these results implicate TIF1 beta as a common transcriptional corepressor for the three distinct subfamilies of KRAB zinc-finger proteins and suggest a high degree of conservation in the molecular mechanism underlying their transcriptional repression activity.

Murine mast cell lines as indicators of early events in mast cell and basophil development

To study early events in mast cell / basophil development, the phenotype of a panel of murine cell lines at various stages of differentiation was determined. Based on the expression on various mast cell-specific proteases and several additional hematopoietic differentiation markers, the cell lines CFTL-15 and MCP5 / L were clearly identified as mast cells, although with a relatively immature phenotype. These two cell lines express the high-affinity IgE receptor alpha-chain, the mouse mast cell protease (MMCP)-5 and the carboxypeptidase A (CPA). Bone marrow-derived mast cells and the transplantable mast cell tumor MTC were shown to express the IgE receptor alpha-chain, MMCP-5 and CPA, as well as the mast cell tryptase MMCP-6 and the chymase MMCP-4, a protease expressed only during late stages of mast cell differentiation. These two cell types thus display a more mature mast cell phenotype. In contrast, the cell lines P815 and 32D cl3 did not express any mast cell differentiation markers. Interestingly, the IC-2 cell line was shown to express several markers for immature mast cells and in addition MMCP-8, a serine protease which may represent a marker for mouse basophils. By antibody staining, almost all IC-2 cells were shown to express MMCP-8. This indicates that individual cells may simultaneously express both mast cell and basophil markers. Moreover, these findings suggest that an early branch point in hematopoietic development where mast cells and basophils have a common precursor cell may exist.

Identification and structural analysis of four serine proteases in a monotreme, the platypus, Ornithorhynchus anatinus

To study the emergence of the major subfamilies of serine proteases during vertebrate evolution, we present here the primary structure of four serine proteases expressed in the spleen of a monotreme, the platypus, Ornithorhynchus anatinus. Partial cDNA clones for four serine proteases were isolated by a PCR-based strategy. This strategy is based on the high level of sequence identity between various members of the large gene family of trypsin-related serine proteases, over two highly conserved regions, those of the histidine and the serine of the catalytic triad. The partial cDNA clones were used to isolate full-length or almost full-length cDNA clones for three of these proteases from a platypus spleen cDNA library. By phylogenetic analysis, these three clones were identified as being the platypus homologues of human coagulation factor X, neutrophil elastase, and a protease distantly related to the T-cell granzymes. The remaining partial clone was found to represent a close homologue of human complement factor D (adipsin). The isolation of these four clones shows that several of the major subfamilies of serine proteases had evolved as separate subfamilies long before the radiation of the major mammalian lineages of today, the monotremes, the marsupials, and the placental mammals. Upon comparison of the corresponding proteases of monotremes and eutherian mammals, the coagulation and complement proteases were shown to display a higher degree of conservation compared to the hematopoietic proteases N-elastase and the T-cell granzymes. This latter finding indicates a higher evolutionary pressure to maintain specific functions in the complement and coagulation enzymes compared to many of the hematopoietic serine proteases.

Mechanism for activation of mouse mast cell tryptase: dependence on heparin and acidic pH for formation of active tetramers of mouse mast cell protease 6

Tryptase, a serine protease with trypsin-like substrate cleavage properties, is one of the key effector molecules during allergic inflammation. It is stored in large quantities in the mast cell secretory granules in complex with heparin proteoglycan, and these complexes are released during mast cell degranulation. In the present paper, we have studied the mechanism for tryptase activation. Recombinant mouse tryptase, mouse mast cell protease 6 (mMCP-6), was produced in a mammalian expression system. The mMCP-6 fusion protein contained an N-terminal 6 x His tag followed by an enterokinase (EK) site replacing the native activation peptide (6xHis-EK-mMCP-6). In the absence of heparin, barely detectable enzyme activity was obtained after enterokinase cleavage of 6xHis-EK-mMCP-6 over a pH range of 5.5-7.5. However, when heparin was present, 6xHis-EK-mMCP-6 yielded active enzyme when enterokinase cleavage was performed at pH 5.5-6.0 but not at neutral pH. Affinity chromatography analysis showed that mMCP-6 bound strongly to heparin-Sepharose at pH 6.0 but not at neutral pH. After enterokinase cleavage of the sample at pH 6.0, mMCP-6 occurred in inactive monomeric form as shown by FPLC analysis on a Superdex 200 column. When heparin was added at pH 6.0, enzymatically active higher molecular weight complexes were formed, e.g., a dominant approximately 200 kDa complex that may correspond to tryptase tetramers. No formation of active tetramers was observed at neutral pH. When injected intraperitoneally, mMCP-6 together with heparin caused neutrophil influx, but no signs of inflammation were seen in the absence of heparin. The present paper thus indicates a crucial role for heparin in the formation of active mast cell tryptase.

MMCP-8, the first lineage-specific differentiation marker for mouse basophils. Elevated numbers of potent IL-4-producing and MMCP-8-positive cells in spleens of malaria-infected mice

In mice infected with the non-lethal malaria parasite Plasmodium chabaudi chabaudi AS, a prominent switch from a Th1 to a Th2 type of response occurs in CD4+ T cells at the time of peak parasitemia or shortly thereafter (9-15 days after infection). This is accompanied by a major increase in IL-4, and a similar decrease in IFN-gamma-producing cells. Non-B-non-T cells have been shown to be the main source of the IL-4 in these mice. The IL-4-producing cells are hyperresponsive to IL-3, indicating mast cell or basophil origin. To further characterize this cell population we have studied various organs at different time points of malarial infection by Northern blot analysis. No significant increase in the expression of any of the classical mouse mast cell serine proteases (MMCP)-1 to 7 or carboxypeptidase A was detected in the spleen during the entire infection. However, a marked increase in the expression of MMCP-8 was observed in the spleen at around day 15 post infection. Isolation of IgE receptor-positive cells from spleen shortly after peak parasitemia led to a prominent enrichment of MMCP-8-expressing cells. Fifty thousand of these cells were, after IL-3 stimulation, found to produce IL-4 to levels comparable with more than one million fully activated T cells. Our results show that basophil-like cells are very potent producers of IL-4 and that IL-4 produced by these cells may be of major importance for the initiation of a Th2 response. In addition, the detection of MMCP-8 in these cells has led to the identification of the first basophil-specific differentiation marker in the mouse.

Expression of lactoferrin in the kidney: implications for innate immunity and iron metabolism

BACKGROUND

Sequestering of free iron by lactoferrin (LF) is important in the defense against bacteria. In a screening for LF expression in various organs, high levels of LF mRNA were detected in human kidney. This indicated that LF is produced by the kidney and that it may participate in innate immunity of this organ.

METHODS AND RESULTS

Antibody staining and in situ hybridization of paraffin-embedded kidney sections showed that LF is expressed in cells lining the distal collecting ducts of the medulla. High levels of both protein and mRNA were detected in these cells. However, a clear difference in the distribution of mRNA and protein within the tissue was observed. LF mRNA was detected along a relatively large portion of the tubuli, whereas LF antigen was found mainly in the very distal regions of the same tubuli. This indicates that LF is released by large regions of the tubuli and possibly reabsorbed in the most distal parts. Using enzyme-linked immunosorbent assay, only very low LF levels were detected in urine.

CONCLUSION

The present study shows that LF is produced by the kidney and that both LF mRNA and protein are distributed in a highly ordered fashion. This latter finding, together with the very low levels of LF detected in urine, indicates that LF may contribute to the immune defense in the kidney by reduction of available free iron in the urine. Other possibilities are that LF may play a role in the iron metabolism by recovering free iron from urine and making it available for metabolic use, and that LF may participate in the antioxidant defense systems protecting the kidney against nonmicrobial oxidative injury, that is, ischemia, reperfusion and inflammation.

Cloning and structural analysis of IgM (mu chain) and the heavy chain V region repertoire in the marsupial Monodelphis domestica

To address the question of the Ig isotype repertoire of non placental mammals, we have examined the Ig expression in the marsupial Monodelphis domestica (grey short tailed opossum). Screening of an opossum spleen cDNA library has previously led to the isolation of full length clones for opossum IgG (gamma chain), IgE (epsilon chain) and IgA (alpha chain). We now present the isolation of several cDNA clones encoding the entire constant regions of the opossum IgM (mu chain). A comparative analysis of the amino acid sequences for IgM from various animal species showed that opossum IgM, within the various animals studied, is the most divergent member of its Ig class. However, it still conforms to the general structure of IgM in other vertebrates. Four Ig classes have now been identified in opossum and only one isotype is apparently present within each Ig class, IgM, IgG, IgA and IgE. Opossum has previously been shown to have a limited VH region diversity, with only two V gene families. Both of these belong to the group III of mammalian VH sequences. This limitation in variability is to some extent compensated for by a large variation in D, P and N regions, both in size and in sequence. However, evidence for the expression of only two functional J segments has so far been detected, which indicates a rather limited diversity also of the J segments in the opossum.

Abnormal mast cells in mice deficient in a heparin-synthesizing enzyme

Heparin is a sulphated polysaccharide, synthesized exclusively by connective-tissue-type mast cells and stored in the secretory granules in complex with histamine and various mast-cell proteases. Although heparin has long been used as an antithrombotic drug, endogenous heparin is not present in the blood, so it cannot have a physiological role in regulating blood coagulation. The biosynthesis of heparin involves a series of enzymatic reactions, including sulphation at various positions. The initial modification step, catalysed by the enzyme glucosaminyl N-deacetylase/N-sulphotransferase-2, NDST-2, is essential for the subsequent reactions. Here we report that mice carrying a targeted disruption of the gene encoding NDST-2 are unable to synthesize sulphated heparin. These NDST-2-deficient mice are viable and fertile but have fewer connective-tissue-type mast cells; these cells have an altered morphology and contain severely reduced amounts of histamine and mast-cell proteases. Our results indicate that one site of physiological action for heparin could be inside connective-tissue-type mast cells, where its absence results in severe defects in the secretory granules.

Comparative analysis of KRAB zinc finger proteins in rodents and man: evidence for several evolutionarily distinct subfamilies of KRAB zinc finger genes

Although the KRAB zinc finger proteins probably constitute the single largest class of transcription factors within the human genome, almost nothing is known about their biological function. To increase our knowledge about this interesting and relatively unexplored family of potent transcriptional repressors, we here present the cloning, structural analysis, and expression study of three novel mouse KRAB zinc finger proteins. In addition, we present an extensive comparative analysis of various members of this gene family based on the structure of the common KRAB A motif. At least three larger subfamilies of KRAB zinc finger proteins are identified: one carrying the classical KRAB A motif only, another holding both a classical KRAB A and a classical KRAB B motif, and a third holding a classical KRAB A and a highly divergent KRAB B domain, named b. A large variation both in size and in primary amino acid sequence was observed in the linker region between the KRAB domain and the C-terminally located zinc finger repeats. This variability indicates that this region is of minor importance for the biological function of KRAB-containing zinc finger proteins. The fact that in many zinc finger genes, the entire or almost the entire linker region is composed of degenerate finger motifs substantiates this conclusion. The absence of identifiable KRAB A and B motifs in the genome of yeast, Saccharomyces cerevisiae, indicates a relatively late appearance of the KRAB domain in evolution and may suggest that the biological functions are restricted to multicellular organisms. In addition, we show that the expression of individual members of one subfamily of KRAB zinc finger genes is restricted to specific hematopoietic cell lineages. This finding suggests that KRAB zinc finger proteins may play a role in lineage commitment, possibly silencing leakage transcription from nonlineage-expressed genes.

Cloning and structural analysis of leydin, a novel human serine protease expressed by the Leydig cells of the testis

We present the cloning and structural analysis of a novel member of the large family of trypsin-related serine proteases. Northern blot analysis shows that this protease, in adult tissues, is expressed almost exclusively in the human testis. In addition, a larger transcript was detected in relatively high abundance in several embryonic tissues, indicating different functions during embryonic and adult life. Sera raised against this protease was used to locate the expression in adult tissues to the testosterone producing cells of the testis, the interstitial Leydig cells. We therefore propose the name leydin for this novel protease. Leydin is clearly distinct from acrosin, the other testis-specific serine protease which is expressed by the spermatocytes. Leydin is probably a two-chain protease such as acrosin, prostasin, and coagulation factor XI. The heavy chain consists of 246 amino acids, corresponding to a molecular mass of 27384 Da and a net charge of +10.76. The size of the light chain is between 9 and 18 amino acids depending on the site of proteolytic cleavage, which remains to be determined. The amino-acid residues surrounding the active site indicate a trypsin-like cleavage specificity. The presence of two dibasic sequences Arg-Arg and Lys-Arg at the N-terminus of the heavy chain indicate that one or more subtilisin-like endopeptidases are responsible for the processing of leydin. However, leydin may also be activated by a trypsin-like enzyme, possibly by auto catalysis.

A kinetic analysis of the expression of mast cell protease mRNA in the intestines of Nippostrongylus brasiliensis-infected rats

To study the kinetics and the phenotype of the mast cells (MC) arising during infection with the nematode Nippostrongylus brasiliensis, monospecific cDNA probes for nine different MC proteases were used in a Northern blot analysis of RNA from the small intestine of infected rats. The expression was analyzed at four individual time points during infection, day 0 (before infection), and days 7, 12 and 16 post infection. A dramatic increase in mRNA for rat mast cell protease (RMCP)-2, the major mucosal MC protease in the rat, was observed, beginning around day 7 after infection and peaking around day 12. At day 16 the expression was already beginning to decline. An almost identical pattern of mRNA expression was detected for the RMCP-8 subfamily of rat MC proteases (RMCP-8, -9 and -10) and for two additional rat serine proteases, the chymases RMCP-3 and -4. No simultaneous increase in the proteases known to be expressed preferentially by mature connective tissue MC (RMCP-1, -6 and -7) was observed. This is consistent with our finding that the expansion of MC in the intestines of parasite-infected animals was limited, almost exclusively, to the mucosal MC population. However, a minor increase in RMCP-5 and MC carboxypeptidase A (CPA) mRNA was detected at day 12 after infection, suggesting a derivation of mucosal MC from an expanding RMCP-5- and CPA-positive population of MC precursors.

Evidence for an early appearance of modern post-switch isotypes in mammalian evolution; cloning of IgE, IgG and IgA from the marsupial Monodelphis domestica

In birds, reptiles and amphibians the IgY isotype exhibits the functional characteristics of both of IgG and IgE. Hence, the gene for IgY most likely duplicated some time during early mammalian evolution and formed the ancestor of present day IgG and IgE. To address the question of when IgY duplicated and formed two functionally distinct isotypes, and to study when IgG and IgA lost their second constant domains, we have examined the Ig expression in a non-placental mammal, the marsupial Monodelphis domestica (grey short-tailed opossum). Screening of an opossum spleen cDNA library revealed the presence of all three isotypes in marsupials. cDNA clones encoding the entire constant regions of opossum IgE (epsilon chain), IgG (gamma chain) and IgA (alpha chain) were isolated, and their nucleotide sequences were determined. A comparative analysis of the amino acid sequences for IgY, IgA, IgE and IgG from various animal species showed that opossum IgE, IgG and IgA on the phylogenetic tree form branches clearly separated from their eutherian counterparts. However, they still conform to the general structure found in eutherian IgE, IgG and IgA. Our findings indicate that all the major evolutionary changes in the Ig isotype repertoire, and in basic Ig structure that have occurred since the evolutionary separation of mammals from the early reptile lineages, occurred prior to the evolutionary separation of marsupials and placental mammals.

Characterization of mouse mast cell protease-8, the first member of a novel subfamily of mouse mast cell serine proteases, distinct from both the classical chymases and tryptases

Using a recently developed PCR-based strategy, a cDNA encoding a novel mouse mast cell (MC) serine protease (MMCP-8) was isolated and characterized. The MMCP-8 mRNA contains an open reading frame of 247 amino acids (aa), divided into a signal sequence of 18 aa followed by a 2-aa activation peptide (Gly-Glu) and a mature protease of 227 aa. The mature protease has an M(r) of 25072, excluding post-translational modifications, a net positive charge of +12 and six potential N-glycosylation sites. MMCP-8 showed a high degree of homology with mouse granzyme B in the critical regions for determining substrate cleavage specificity, indicating that MMCP-8, similar to granzyme B, preferentially cleaves after Asp residues. A comparative analysis of the aa sequence of MMCP-8 with other hematopoietic serine proteases shows that it is more closely related to cathepsin G and T cell granzymes than to the MC chymases. We therefore conclude that MMCP-8 belongs to a novel subfamily of mouse MC proteases distinct from both the classical chymases and tryptases. Southern blot analysis of BALB/c genomic DNA indicated that only one MMCP-8 gene (or MMCP-8 like gene) is present in the mouse genome. Northern blot analysis of rodent hematopoietic cell lines revealed high levels of MMCP-8 mRNA in a mouse connective tissue MC-like tumor line. However, MMCP-8 mRNA could not be detected in mouse liver, intestine, lung or ears, indicating very low expression in normal tissues. Analysis of the expression of different MMCP in the tissues of Schistosoma mansoni-infected BALB/c mice showed a strong increase in MMCP-8 levels in the lungs but not in the intestines of infected animals, suggesting the presence of a novel subpopulation of MC in the lungs that expressed MMCP-8, either alone or in combination with MMCP-5 and carboxypeptidase A. The dramatic increase in MMCP-1 and MMCP-2 levels but not of MMCP-8 in the intestines of parasitized animals also shows that MMCP-8 is not expressed in mucosal MC in the mouse. This latter is in clear contrast to what has been observed in the rat where the MMCP-8 homologues, RMCP-8, -9 and -10, can be considered as true mucosal MC proteases.

The role of the propeptide for processing and sorting of human myeloperoxidase

Myeloperoxidase (MPO), stored in azurophil granules of neutrophils, is critical for an optimal oxygen-dependent microbicidal activity of these cells. Pro-MPO goes through a stepwise proteolytic trimming with elimination of an amino-terminal propeptide to yield one heavy and one light polypeptide chain. The propeptide of MPO may have a role in retention and folding of the nascent protein into its tertiary structure or in targeting of pro-MPO for processing and storage in granules. A propeptide-deleted pro-MPO mutant (MPODeltapro) was constructed to determine if deletion of the propeptide interferes with processing and targeting after transfection to the myeloid 32D cell line. Transfection of full-length cDNA for human MPO results in normal processing and targeting of MPO to cytoplasmic dense organelles. Although the efficiency of incorporation was lower for MPODeltapro, both pro-MPO and MPODeltapro showed heme incorporation indicating that the propeptide is not critical for this process. Deletion of the propeptide results in synthesis of a protein that lacks processing into mature two-chain forms but rather is degraded intracellularly or secreted. The finding of continued degradation of MPODeltapro in the presence of lysosomotrophic agents or brefeldin A rules out that the observed degradation takes place after transfer to granules. Intracellular pro-MPO has high mannose oligosaccharide side chains, whereas stored mature MPO was found to have both high mannose and complex oligosaccharide side chains as judged by only partial sensitivity to endoglycosidase H. The propeptide may normally interfere with the generation of certain complex oligosaccharide chain(s) supported by the finding of high mannose side chains in secreted pro-MPO and lack of them in MPODeltapro that contained complex oligosaccharide side chains only. In conclusion, elimination of the propeptide of pro-MPO blocks the maturation process and abolishes accumulation of the final product in granules suggesting a critical role of the propeptide for late processing of pro-MPO and targeting for storage in granules.

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.