Whole-genome sequence and mass spectrometry study of the snow blight fungus Phacidium infestans (Karsten) DSM 5139 growing at freezing temperatures

Phacidium infestans (synonym Gremmenia infestans) is a significant pathogen that impacts Pinus species across the northern regions of Europe and Asia. This study introduces the genome sequence of P. infestans Karsten DSM 5139 (Phain), obtained through Pacbio technology. The assembly resulted in 44 contigs, with a total genome size of 36,805,277 bp and a Guanine-Cytosine content of 46.4%. Genome-mining revealed numerous putative biosynthetic gene clusters that code for virulence factors and fungal toxins. The presence of the enzyme pisatin demethylase was indicative of the potential of Phain to detoxify its environment from the terpenoid phytoalexins produced by its host as a defense mechanism. Proteomic analysis revealed the potential survival strategies of Phain under the snow, which included the production of antifreeze proteins, trehalose synthesis enzymes, desaturases, proteins related to elongation of very long-chain fatty acids, and stress protein responses. Study of protein GH11 endoxylanase expressed in Escherichia coli showed an acidic optimum pH (pH 5.0) and a low optimum temperature (45 °C), which is reflective of the living conditions of the fungus. Mass spectrometry analysis of the methanol extract of Phain, incubated at - 3 °C and 22 °C, revealed differences in the produced metabolites. Both genomic and mass spectrometry analyses showed the ability of Phain to adapt its metabolic processes and secretome to freezing temperatures through the production of osmoprotectant and cryoprotectant metabolites. This comprehensive exploration of Phain's genome sequence, proteome, and secretome not only advances our understanding of its unique adaptive mechanisms but also expands the possibilities of biotechnological applications.

Preferential Degradation of Soluble Fibrin Monomers in Streptokinase-activated Plasma

Degradation of 125I-labelled fibrin monomers and 125I-fibrinogen in streptokinase-activated plasma was investigated. Release of the label proceeded at a much higher rate from soluble fibrin monomer complexes than from fibrinogen until ca. 70% of the label was recovered in the serum. It is concluded that the fibrinolytic system has an essentially higher affinity to monomers than to fibrinogen, but that the specificity of the monomers as substrate may be limited to the early steps of degradation. It is suggested that the preferential splitting of fibrin monomer complexes may be important in the body’s defence against pathological fibrin formations derived from paracoagulable fibrin.

Comparison of Ethanol and Protamine Tests in Demonstration of Soluble Fibrin and Early Products of Fibrin Degradation

Performance and applicability of ethanol-induced gelation and protamine-induced paracoagulation for the demonstration of soluble fibrin monomer complexes and fragment Xo complexes was studied by using 1. fibrin monomer plasma prepared by adding small amounts of thrombin to plasma, 2. clot lysis products, and 3. thrombin -treated mixture of fibrinogen degradation products and plasma. To increase the specificity of the protamine tests only visible fibrin strand formation was recorded as positive. In addition to qualitative tests the amount of paracoagulable material was measured by a spectrophotometric method.

The ethanol gelation test proved very simple, reproducible and considerably more sensitive than the protamine tests in demonstrating soluble fibrin monomer complexes, irrespective of whether fibrinogen degradation products were present or not. On the other hand, the protamine tests were clearly superior for demonstration of clot lysis products (fragment Xo complexes). Therefore it seems advisable to perform both types of tests when screening for intravascular coagulation.

Improved xylanase production by Trichoderma reesei grown on L-arabinose and lactose or D-glucose mixtures

Trichoderma reesei Rut C-30 was grown on eight different natural or rare aldopentoses as the main carbon source and on mixtures of an aldopentose with D-glucose or lactose. The fungal cells consumed all aldopentoses tested, except L-xylose and L-ribose. The highest total xylanase and cellulase activities were achieved when cells were grown on L-arabinose as the main carbon source. The total xylanase activity produced by cells grown on L-arabinose was even higher than that produced by cells grown on an equal amount of lactose. In co-metabolism of D-glucose (15 g l(-1)) and L-arabinose (5 g l(-1)), the total volumetric and specific xylanase productivities were improved (derepressed) approximately 23- and 18-fold, respectively, compared to a cultivation on only D-glucose (20 g l(-1)). In a similar experiment, in which cells were grown on a mixture of lactose and L-arabinose, the xylanase productivity was approximately doubled, compared to a cultivation on only lactose. The cellulase productivities, however, were not improved by the addition of L-arabinose. Compared with a typical industrial fungal enzyme production process with lactose as the main carbon source, better volumetric and specific xylanase productivities were achieved both on a lactose/arabinose mixture and on a glucose/arabinose mixture.

Thermostability of endo-1,4-beta-xylanase II from Trichoderma reesei studied by electrospray ionization Fourier-transform ion cyclotron resonance MS, hydrogen/deuterium-exchange reactions and dynamic light scattering

Endo-1,4-beta-xylanase II (XYNII) from Trichoderma reesei is a 21 kDa enzyme that catalyses the hydrolysis of xylan, the major plant hemicellulose. It has various applications in the paper, food and feed industries. Previous thermostability studies have revealed a significant decrease in enzymic activity of the protein at elevated temperatures in citrate buffer [Tenkanen, Puls and Poutanen (1992) Enzyme Microb. Technol. 14, 566-574]. Here, thermostability of XYNII was investigated using both conventional and nanoelectrospray ionization Fourier-transform ion cyclotron resonance MS and hydrogen/deuterium (H/D)-exchange reactions. In addition, dynamic light scattering (DLS) was used as a comparative method to observe possible changes in both tertiary and quaternary structures of the protein. We observed a significant irreversible conformational change and dimerization when the protein was exposed to heat. H/D exchange revealed two distinct monomeric protein populations in a narrow transition temperature region. The conformational change in both the water and buffered solutions occurred in the same temperature region where enzymic-activity loss had previously been observed. Approx. 10-30% of the protein was specifically dimerized when exposed to the heat treatment. However, adding methanol to the solution markedly lowered the transition temperature of conformational change as well as increased the dimerization up to 90%. DLS studies in water confirmed the change in conformation observed by electrospray ionization MS. We propose that the conformational change is responsible for the loss of enzymic activity at temperatures over 50 degrees C and that the functioning of the active site in the enzyme is unfeasible in a new, more labile solution conformation.

A combination of weakly stabilizing mutations with a disulfide bridge in the α-helix region of Trichoderma reesei endo-1,4-β-xylanase II increases the thermal stability through synergism

Thermal stability and other functional properties of Trichoderma reesei endo-1,4-beta-xylanase II (XYNII; family 11) were studied by designed mutations. Mutations at three positions were introduced to the XYNII mutant containing a disulfide bridge (S110C-N154C) in the alpha-helix. The disulfide bridge increased the half-life of XYNII from less than 1 min to 14 min at 65 degrees C. An additional mutation at the C-terminus of the alpha-helix (Q162H or Q162Y) increased the half-life to 63 min. Mutations Q162H and Q162Y alone had a stabilizing effect at 55 degrees C but not at 65 degrees C. The mutations N11D and N38E increased the half-life to about 100 min. Due to the stabilizing mutations the pH stability increased in a wide pH range, but at the same time the activity decreased both in acidic and neutral-alkaline pH, the pH optimum being at pH region 5-6. There was no essential difference between the specific activities of the mutants and the wild-type XYNII.

Mucin MUC1 is seen in cell surface protrusions together with ezrin in immunoelectron tomography and is concentrated at tips of filopodial protrusions in MCF-7 breast carcinoma cells

MUC1, a transmembrane member of the mucin family, is believed to have anti-adhesive properties because of its highly sialylated, extended, and rigid rod-like conformation. The ERM proteins (ezrin, radixin, and moesin) function as membrane-cytoskeletal linkers. MUC1 and ezrin are enriched in microvilli in MCF-7az breast carcinoma cells. Similar localization was also found in peripheral membrane areas and in filopodium-like protrusions. Whereas ezrin was consistently detected in the cell-cell contact region, MUC1 was less frequently found there. MUC1 was distinctly expressed in long filopodial protrusions and was highly concentrated at their tips, which also contained ezrin, whereas F-actin was found along the stalk. This localization of MUC1 suggests a role for MUC1 in transient cell structures of migrating cells and transient cell adhesion. No direct association has yet been found between MUC1 and ezrin. However, both MUC1 and ezrin had a similar overall distribution pattern in microvilli and filopodium-like protrusions in immunoelectron tomography. In addition, MUC1 and ezrin showed spatial association, because several 10-nm gold particles used to decorate ezrin were seen in the vicinity close to the clusters of 5-nm gold particles decorating MUC1. Therefore, MUC1 appears to be associated with ezrin, but the nature of this association requires further study.

Genomic structure of the human ezrin gene

The ERM proteins, ezrin, radixin, and moesin, act as linkers between the plasma membrane and actin cytoskeleton. They are involved in a variety of cellular functions, such as cell adhesion, migration, and the organization of cell surface structures, and are highly homologous, both in protein sequence and in functional activity, with merlin/schwannomin, a neurofibromatosis-2-associated tumor-suppressor protein. We report here the genomic structure and intron junction sequences of the human ezrin gene. Ezrin consists of 13 exons and spans approximately 24 kb genomic DNA. The coding parts of the exons range in size from 12 bp to 275 bp and the introns from 182 bp to 7 kb. The genomic structures of ezrin and moesin are highly conserved, suggesting their recent divergence. Radiation hybrid mapping has refined the location of ezrin to the interval between D6S442 and D6S281.

Structure-function relationships in the ezrin family and the effect of tumor-associated point mutations in neurofibromatosis 2 protein

Ezrin, radixin and moesin (ERM proteins) link cell adhesion molecules to the cytoskeleton, modulate cell morphology and cell growth and are involved in Rho-mediated signal transduction. Merlin, the tumor suppressor in neurofibromatosis 2, is a diverged member of the ezrin family, but its function is at least partially similar to the ERM proteins. In the N-domain, the ezrin family belongs to the band 4.1 superfamily. Secondary structure predictions made separately for the ezrin and band 4.1-tyrosine phosphatase families give a similar pattern for the homologous N-domains, indicating that both families have a similar binding site for the integral membrane proteins. The alpha-domain shows a strong coiled-coil prediction, that can be involved in the protein dimerization. The C-terminal actin-binding site in the ERM proteins and the actin-binding helix in the villin headpiece have a common amino acid motif. In merlin, the published tumor-associated single amino acid mutations in the N-domain are located in the conserved sites, and they affect mainly the predicted helices and strands, indicating that these mutations cause the disease primarily by disturbing the protein structure. In the alpha- and C-domains, some of the mutations break the helical structures. Some known mutations are observed at a site potentially interacting with cell adhesion molecules. We will also discuss the implications of the evolutionary information and the actin-binding models in the ezrin family.

The ezrin protein family: membrane-cytoskeleton interactions and disease associations

Ezrin, radixin, moesin and merlin form a subfamily of conserved proteins in the band 4.1 superfamily. Ezrin protein subfamily members act as linkers between the plasma membrane and the cytoskeleton. Members of the subfamily have been shown to interact with each other, with cell adhesion molecules such as CD44 and with F-actin. Recent data indicate that intercellular adhesion molecules 1 and 2 also interact with ezrin. The proteins are also involved in the redistribution of intercellular adhesion molecules and the organization of cell membrane structures. Merlin is a tumor suppressor that is involved in tumorigenesis of schwannomas and meningiomas. Merlin has the same overall protein structure as the other proteins in the subfamily but may have partially distinct functions.

Neurofibromatosis 2 tumor suppressor protein colocalizes with ezrin and CD44 and associates with actin-containing cytoskeleton

Neurofibromatosis 2 (NF2) protein (merlin; schwannomin) is a tumor suppressor involved in tumorigenesis of NF2-associated and sporadic schwannomas and meningiomas. The protein shares the domain structure of three homologous proteins: ezrin, radixin and moesin (ERM). ERM proteins function as membrane organizers and may act as linkers between plasma membrane molecules, such as CD44 and ICAM-2, and the cytoskeleton. We analyzed the distribution and effects of transfected NF2 protein in COS-1, CHO and 293 cells, and endogenous NF2 protein in U251 glioma cells. The distribution was compared to ezrin, CD44 and F-actin. Both transfected and endogenous NF2 protein localized underneath the plasma membrane in a pattern typical of an ERM protein. In COS-1 transfectants, NF2 protein typically codistributed with ezrin but, in cells with poorly developed actin cytoskeleton, it replaced ezrin in filopodia and ruffling edges. NF2 protein colocalized with CD44, which in transfected cells accumulated into restructured cell membrane protrusions. The association of CD44 and NF2 protein was further suggested by binding of CD44 from cellular lysates to recombinant NF2 protein. Interaction between NF2 protein and the actin-containing cytoskeleton was indicated by partial colocalization, by cytochalasin B-induced coclustering, and by retention of NF2 protein in the detergent-insoluble fraction. Transfected NF2 protein induced morphogenic changes. The cells contained restructured membrane extensions and blebs, and CHO cells expressing NF2 protein were more elongated than control transfectants. In conclusion, NF2 protein possesses functional properties of an ERM family member.

ICAM-2 redistributed by ezrin as a target for killer cells

Very little is known about the receptors and target molecules involved in natural killer (NK) cell activity. Here we present a model system in which interleukin-2-activated killing by NK cells depends on the intercellular adhesion molecule ICAM-2 and is regulated by the distribution of ICAM-2. The level of ICAM-2 expression in NK-sensitive and resistant cells is similar, but in sensitive cells ICAM-2 is concentrated into bud-like cellular projections known as uropods, whereas in resistant cells it is evenly distributed. The cytoskeletal-membrane linker protein ezrin is also localized in uropods. Transfection of human ezrin into NK-resistant cells induces uropods formation, redistribution of ICAM-2 and ezrin, and sensitizes target cells to interleukin-2-activated killing. These results reveal a new mechanism of target-cell recognition: cytotoxic cells recognize adhesion molecules that are already present on normal cells, but in diseased cells are concentrated into a biologically active cell-surface region by cytoskeletal reorganization. The results also highlight the importance of cytoskeletal interactions in the regulation of ICAM-2-mediated adhesive phenomena.

Ezrin expression in stromal cells of capillary hemangioblastoma. An immunohistochemical survey of brain tumors

Ezrin is a cytoskeleton-associated protein that appears to link actin filaments to the plasma membrane. Immunocytochemical studies suggest that ezrin is expressed in epithelial cells but not in mesenchymal cells. In addition, ezrin is expressed by certain epithelial tumors, such as renal cell adenocarcinomas. Ezrin serves as a tyrosine kinase substrate, and is phosphorylated in epidermal growth factor-stimulated cells. Ezrin may thus mediate regulatory signals in different cell functions. We studied the distribution of ezrin in 104 cases of primary tumors of the central nervous system (CNS) by immunocytochemistry. Special interest was focused on capillary hemangioblastoma, owing to its resemblance to renal cell adenocarcinoma, and on malignant gliomas, owing to their frequent epidermal growth factor receptor amplification. The stromal cells of hemangioblastomas were found to be strongly positive for ezrin. No expression was detected in gliomas and, except for hemangioblastomas, ezrin expression was restricted to those few CNS tumors that show epithelial differentiation, ie, choroid plexus papillomas, craniopharyngiomas, ependymomas, and cysts. The diffuse cytoplasmic expression of ezrin in the stromal cells of capillary hemangioblastoma may indicate that stromal cells overexpress ezrin or express ezrin with deficient binding properties.

Ezrin has a COOH-terminal actin-binding site that is conserved in the ezrin protein family

Ezrin, previously also known as cytovillin, p81, and 80K, is a cytoplasmic protein enriched in microvilli and other cell surface structures. Ezrin is postulated to have a membrane-cytoskeleton linker role. Recent findings have also revealed that the NH2-terminal domain of ezrin is associated with the plasma membrane and the COOH-terminal domain with the cytoskeleton (Algrain, M., O. Turunen, A. Vaheri, D. Louvard, and M. Arpin. 1993. J. Cell Biol. 120: 129-139). Using bacterially expressed fragments of ezrin we now demonstrate that ezrin has an actin-binding capability. We used glutathione-S-transferase fusion proteins of truncated ezrin in affinity chromatography to bind actin from the cell extract or purified rabbit muscle actin. We detected a binding site for filamentous actin that was localized to the COOH-terminal 34 amino acids of ezrin. No binding of monomeric actin was detected in the assay. The region corresponding to the COOH-terminal actin-binding site in ezrin is highly conserved in moesin, actin-capping protein radixin and EM10 protein of E. multilocularis, but not in merlin/schwannomin. Consequently, this site is a potential actin-binding site also in the other members of the protein family. Furthermore, the actin-binding site in ezrin shows sequence homology to the actin-binding site in the COOH terminus of the beta subunit of the actin-capping protein CapZ and one of the potential actin-binding sites in myosin heavy chain. The actin-binding capability of ezrin supports its proposed role as a membrane-cytoskeleton linker.

Ezrin contains cytoskeleton and membrane binding domains accounting for its proposed role as a membrane-cytoskeletal linker

Ezrin, a widespread protein present in actin-containing cell-surface structures, is a substrate of some protein tyrosine kinases. Based on its primary and secondary structure similarities with talin and band 4.1 it has been suggested that this protein could play a role in linking the cytoskeleton to the plasma membrane (Gould, K.L., A. Bretscher, F.S. Esch, and T. Hunter. 1989. EMBO (Eur. Mol. Biol. Organ.), J. 8:4133-4142; Turunen, O., R. Winqvist, R. Pakkanen, K.-H. Grzeschik, T. Wahlström, and A. Vaheri. 1989. J. Biol. Chem. 264:16727-16732). To test this hypothesis, we transiently expressed the complete human ezrin cDNA, or truncated cDNAs encoding the amino- and carboxy-terminal domains of the protein, in CV-1 cells. Protein epitope tagging was used to unambiguously determine the subcellular distribution of the protein encoded by the transfected cDNA. We show that this protein is concentrated underneath the dorsal plasma membrane in all actin-containing structures and is partially detergent insoluble. The amino-terminal domain displays the same localization but is readily extractable by nonionic detergent. The carboxy-terminal domain colocalizes with microvillar actin filaments as well as with stress fibers and remains associated with actin filaments after detergent extraction, and with disorganized actin structures after cytochalasin D treatment. Our results clearly demonstrate that ezrin interacts with membrane-associated components via its amino-terminal domain, and with the cytoskeleton via its carboxy-terminal domain. The amino-terminal domain could include the main determinant that restricts the entire protein to the cortical cytoskeleton in contact with the dorsal plasma membrane and its specialized microdomains such as microvilli, microspikes and lamellipodia.

Cytovillin, a microvillar Mr 75,000 protein. cDNA sequence, prokaryotic expression, and chromosomal localization

Cytovillin is a microvillar cytoplasmic peripheral membrane protein, with prominent expression in vivo in placental syncytiotrophoblasts and certain human tumors. Cytovillin cDNA was cloned from a human placental lambda gt11 library using affinity purified antibodies. The identity of cytovillin cDNA clones was confirmed by expression of cytovillin in Escherichia coli and using antibodies raised against the expressed fusion protein in comparison with antibodies against cytovillin purified from cultured human choriocarcinoma cells. In these cells Northern blotting analysis identified a major 3.5-kilobase cytovillin mRNA. The cDNA encodes a protein of 575 amino acids corresponding to a molecular weight of 68,084. According to secondary structure prediction, cytovillin is a hydrophilic protein with an extensive internal alpha-helical region ending in a sequence of 7 consecutive prolines. The predicted alpha-helical region showed limited homology to alpha-helical regions of cytoskeletal proteins and certain other proteins, but no extensive homologies were found in the cytovillin cDNA or the deduced amino acid sequence to other registered DNA or protein sequences. Southern blot analysis of a DNA panel of human mouse somatic cell hybrids localized the cytovillin gene to the end of the long arm of chromosome 6 (6q22-q27). Our results show that cytovillin is representative of a novel class of microvillar proteins.

Redistribution of Mr 75,000 plasma membrane protein, cytovillin, into newly formed microvilli in herpes simplex and Semliki Forest virus infected human embryonal fibroblasts

We have previously purified an Mr 75,000 protein from cultured human JEG-3 choriocarcinoma cells and showed that this protein is specifically confined to the cytoplasmic side of JEG-3 microvillar membranes. Recently, the Mr 75,000 protein, designated as cytovillin, was found to be expressed also in several other cultured human cell lines and strains, in which it was detected in microvillus-related structures. We now demonstrate the redistribution of cytovillin in herpes simplex type 1 (HSV-1) and Semliki Forest virus (SFV) infected human embryonal fibroblasts. Virus infection induced rapidly numerous microvilli on the apical cell surfaces, and cytovillin was enriched into these newly formed structures as shown by indirect immunofluorescence and immunoferritin electron microscopy. In mock-infected cells treated with the anti-cytovillin antibodies a small amount of ferritin particles and faint fluorescence was detected along the smooth plasma membrane. Only occasional cell surface protrusions were observed in these cells. The enrichment of the cytovillin was first seen 2 h after infection. The isoelectric point (IP) and the mobility of the cytovillin polypeptide in sodium dodecyl sulfate polyacrylamide gel electrophoresis was not altered after this redistribution, suggesting that the protein was not significantly modified during infection. Five RNA+ SFV mutants (ts-1, ts-2, ts-3, ts-5, ts-7) with temperature-sensitive defects in processing and transport of viral envelope glycoproteins to the plasma membrane induced microvilli at the restrictive temperature (39 degrees C) as the wild type virus.(ABSTRACT TRUNCATED AT 250 WORDS)

Microvillus-specific Mr 75,000 plasma membrane protein of human choriocarcinoma cells

We have previously purified from cultured JEG-3 choriocarcinoma cells an Mr 75,000 protein, originally detected using antibodies to a retrovirus-related synthetic peptide. Using polyclonal antibodies, we have now localized this protein immunocytochemically in JEG-3 cells at both light and electron microscopic levels. In immunofluorescence microscopy of saponin-permeabilized cells, the antigen appeared as dots and short strands at the apical cell surface. In pre-embedding immunoperoxidase electron microscopy, the Mr 75,000 protein was specifically localized to microvilli on the apical cell surface. Immunoferritin electron microscopy was used to assess more quantitatively the antigen distribution in the plane of the plasma membrane, and to define the position of the antigenic site(s) with respect to the membrane. The immunoferritin results confirmed the microvillus specificity of the Mr 75,000 protein and showed that the antigenic portion of the protein is within a few nanometers from, and on the cytoplasmic side of, the lipid bilayer. In detergent extraction experiments, the Mr 75,000 antigen was highly enriched in the soluble fractions. These results demonstrate that the Mr 75,000 protein is a membrane protein highly specific for microvilli.

Human chronic lymphocytic leukaemia. Surface markers and activation of lymphocytes

Cell surface markers and the responses of lymphocytes to T- and B-cell mitogens were studied in 10 patients with CCL. T cells were identified as cells rosetting with sheep red blood cells (SRBC), and S-Ig was used as a marker for B lymphocytes. Most cells from all patients had a detectable amounts of S-Ig, and the percentage of cells rosetting with SRBC was low in all cases. Of the lymphocytes from these patients, 3-74% (mean 33%) were positive for the acid esterase (ANAE), which has been claimed to be a T-cell marker. However, some patients had cells that were positive for both S-Ig and ANAE. Acid esterase staining is therefore not a valid T-cell marker in chronic lymphocytic leukaemia. In cultures containing the T-cell mitogen leucoagglutinin (LA) and the T- and B-cell mitogen pokeweed mitogen (PWM) the reactivity of the lymphocytes was low. The cells responded vigorously to the T- and B-cell mitogen protein A (PA); however, the response was serum-dependent, being strong in a culture medium containing foetal calf serum (FCS), but impaired in the presence of human AB serum. Only 1 patient had cells that responded to the B-cell mitogen LPS.

Cell surface markers in cord blood leucocytes after stimulation with lipopolysaccharide B

T- and B-lymphocyte markers were studied in cord blood cells cultured with lipopolysaccharide B (LPS). Cells cultured with leucoagglutinin (LA) and pokeweed mitogen (PWM) were used as controls. LPS-induced lymphoblasts were negative for surface Ig, positive for intracellular Ig and did not form rosettes with sheep red blood cells (SRBC). LA-activated cells formed rosettes with SRBC, while PWM cultures showed a varying proportion of surface Ig-positive or SRBC rosetting cells, dependent on the time of culture. About 50% of both LA- and LPS-activated lymphoblasts formed EA rosettes (specific for Fc receptors) and EAC rosettes (specific for complement receptors). The response of foetal cells to LPS was reduced when lymphocytes obtained from Isopaque-Ficoll gradients were passed through nylon wool columns, whereas this procedure led to an increased response to LA. Thus LPS-activated foetal leucocytes are B lymphocytes expressing intracellular but not surface Ig.

Activation of lymphocytes in CLL by protein A from Staphylococcus aureus

The mitogenic activity of protein A (PA), leucoagglutinin (LA) and pokeweed mitogen (PWM) was tested in six cases of chronic lymphatic leukaemia (CLL), and the response to PA and LA in six healthy controls. The effect of foetal calf serum (FCS) and pooled human AB serum in the cultures was tested in two patients. The response to LA in the patients was about one tenth of that in the controls. The response to PA was strong both in patients and in healthy controls. However, in lymphocytes from CLL patients this response was serum-dependent, being very strong with FCS in the culture medium, but absent when the medium contained human AB serum. Lymphocytes from normal controls responded to PA in the presence of AB serum.

Stimulation of human fetal lymphocytes by lipopolysaccharide B in culture. Studies on cells circulating in maternal blood

Lipopolysaccharide B (LPS) was used in attempts to stimulate fetal cells circulating in the maternal blood during pregnancy. Crystalline leukoagglutinin (LA), the mitogenic properties of which are identical with those of phytohemagglutinin, was used as a reference mitogen. When artificial mixtures of varying proportions of lymphocytes from mothers (XX) and their newborn male infants (XY) were co-cultured in the presence of these mitogens. LPS brought about a definite enrichment of XY mitoses, indicating that even under these conditions of co-culture, LPS preferentially, though not exclusively, stimulates the infant cells. When cells from the blood of 13 women pregnant in the second trimester with a male fetus were cultured with LPS as a mitogen, all mitoses were found to be XX. Since interphase Y chromatin occurred in uncultured lymphocytes from these women (cells containing Y chromatin were found in 5 out of 6 women tested), we conclude that LPS is unable to stimulate, or at least induce mitoses, in fetal cells circulating in the blood of pregnant women. The nature of these cells is discussed.

Stimulation of human fetal lymphocytes by lipopolysaccharide B in culture

Cultures of Isopaque-Ficoll-isolated lymphocytes from three human sources were compared with respect to the effect of mitogens. The cell sources were maternal blood immediately after delivery, cord blood, and blood obtained by heart puncture of 10-20-week aborted fetuses. Lipopolysaccharide B (LPS) induced incorporation of tritiated thymidine, blastic transformation, and mitotic activity in cord and fetal, but not maternal, cells. The stimulation reached a maximum on days 4-8 of culture. It was stronger than the spontaneous transformation often displayed by fetal cells. If fetal cells spontaneously occurring in the blood of pregnant women were to react in a similar way, it should be possible to selectively stimulate the fetal cells with LPS. Such transformed fetal cells could then be isolated from cultures of maternal blood samples and used for antenatal diagnosis of fetal disease.