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PubMed1983

Relative importance of C4 binding protein in the modulation of the classical pathway C3 convertase in patients with systemic lupus erythematosus.

Serum concentrations of C1q, C4, C4 binding protein (C4bp), C3 and C2 haemolytic activity have been measured in 110 samples from 20 patients with systemic lupus erythematosus (SLE). Significant reductions in comparison to normal levels were found in the mean serum concentrations of C4, C3 and C4bp as well as C2 haemolytic activities. For patients serum concentrations of C4 correlated with C2 haemolytic activities (r = 0.91) and C4bp (r = 0.79); the C2 haemolytic levels correlated with the concentration of C4b (r = 0.72). It is concluded that serum concentrations of the complement components C4 and C2, which are the constituents of the classical pathway C3 convertase, are regulated by C4bp in vivo. Further metabolic studies are required to determine the causes of decreased serum concentrations of C4bp in patients with SLE.

Carrier Proteins↗
PubMed1983

Genetic polymorphism of human C4-binding protein.

Two different forms of human C4-bp, C4-bp A and C4-bp B, have been identified by isoelectric focusing (IEF) of neuraminidase-treated EDTA-plasma samples. Family studies demonstrate Mendelian segregation of these forms, indicating that they are under gentic control. This conclusion is supported by IEF analysis of the two variants purified by affinity chromatography. Under completely denaturing conditions, C4-bp B was found to be composed of two subunits that focused at different pH, whereas C4-bp A contains only the more basic one. These results suggest that a single autosomal locus with at least two codominant alleles coding for the subunits controls the IEF variation of C4-bp in humans. The allele designated C4BP*1 codes for a subunit that, after neuraminidase treatment, focuses at pH = 6.65. The allele C4BP*2 codes for a different subunit that focuses at pH = 6.60. The C4-bp A phenotype corresponds to the genotype C4BP*1,C4BP*1 and the phenotype C4-bp B to the genotype C4BP*1,C4BP*2. The phenotype corresponding to the C4BP*2,C4BP*2 homozygous genotype has not been encountered thus far. Initial linkage data indicate that the C4BP locus is not closely linked to either the HLA or to the C3 loci.

Animals↗
PubMed1993

[Protein S deficiency, acute phase reaction and thrombosis].

Protein S deficiency increases risk of thrombosis. At present, we have information on 63 Norwegian individuals with hereditary protein S deficiency belonging to 25 different families. 42 of the individuals have experienced at least one thromboembolic episode, and seven a cerebral infarction before the age of 70 years. The amount of free protein S in plasma is dependent on variation of the acute phase protein C4b-binding protein (C4bBP). Acute phase response with increased C4bBP induces free protein S deficiency, and increases risk of thrombosis. In patients with protein S deficiency, warfarin may reduce free protein S to critically low levels, and thus explain why, in some patients, recurrent thrombosis occurs during warfarin treatment. In this situation, warfarin should be replaced by heparin.

Acute-Phase Proteins↗
PubMed1995

Production of transforming growth factor alpha by human leukemia cells (HL-60 and U-937) during monocytic differentiation.

We have previously demonstrated that human promyelocytic HL-60 cells express transforming growth factor-alpha (TGF-alpha) during granulocytic differentiation. The present experiments were carried out in order to determine whether cells differentiated towards monocytes/macrophages will analogously express the TGF-alpha proto-oncogene product. HL-60 cells were induced to differentiate with 1 microM 1,alpha 25-dihydroxycholecalciferol (vitamin D3), and the human monocytoid cell line, U-937, was induced with 1 microM retinoic acid (RA), 0.1 microM vitamin D3, or 0.16 microM phorbol-12-myristate-13-acetate (PMA), ie experimental protocols known to induce monocyte/macrophage differentiation in these cells. In HL-60 cells, lacking constitutive TGF-alpha mRNA, vitamin D3 caused expression of the TGF-alpha gene and protein as demonstrated by Northern blot analysis and enzyme-linked immunoabsorbant assay (ELISA). In U-937 cells, showing constitutive TGF-alpha expression, RA but not vitamin D3 or PMA, caused marked increase in TGF-alpha mRNA (approximately 5-fold) and protein (approximately 3-fold) levels. In both cell lines the increase in TGF-alpha mRNA was evident within 24 h and continued throughout the observation period. Thus, it is established that differentiation of human leukemia cells towards monocytes/macrophages may be accompanied by TGF-alpha gene and protein expression in vitro. This is in conformity with the observed ability of mature activated macrophages to produce TGF-alpha.

Antigens, CD↗
PubMed1995

HIMeg-1, a cell line derived from a CML patient, is capable of monocytic and megakaryocytic differentiation.

We have characterized HIMeg-1, a subclone of the promegakaryoblastic cell line HIMeg, in terms of its capability of proliferation and differentiation when it is exposed to various agents. We observed that phorbol 12-myristate 13-acetate (PMA) arrested HIMeg-1 growth and induced expression of monocytic surface antigens CD11c and CD14, but not the megakaryocytic surface antigen CD14a. In addition, PMA treatment of HIMeg-1 led to rapid activation of mRNA expression of egr-1, a transcription factor involved in regulating differentiation of hematopoietic progenitor cells. On the other hand, treatment of HIMeg-1 with the activated peripheral blood lymphocyte-conditioned medium (PBL-CM) resulted in greatly enhanced incorporation of 3H-thymidine into newly synthesized DNA. This enhanced 3H-thymidine incorporation appears to be specific to HIMeg-1 since the same concentrations of PBL-CM had little effect on the growth of the megakaryoblastic leukemia cell line SAM-1. The PBL-CM-induced DNA synthesis in HIMeg-1 was associated with activation of CD41a and CD41b surface antigen expression and down-regulation of expression of the erythroid marker glycophorin A and the early myeloid surface antigen CD33. HIMeg-1 capable of responding differentially to PMA and PBL-CM by changing its growth rate as well as its differentiation patterns will provide an ideal model to study the underlying mechanism regulating lineage restriction of hematopoietic progenitor cells.

Antigens, CD↗
PubMed1995

Granulocyte-macrophage colony-stimulating factor, phorbol ester, and sodium butyrate induce the CD11c integrin gene promoter activity during myeloid cell differentiation.

To analyze the activity of the CD11c promoter during myeloid differentiation without the limitations of transient expression systems, we have stably transfected the myeloid U937 cell line with the pCD11C361-Luc plasmid, in which the expression of the firefly luciferase cDNA is driven by the CD11c promoter region -361/+43, previously shown to confer myeloid specificity to reporter genes. The stable transfectants (U937-C361) retained the ability to differentiate in response to phorbol-ester (PMA), sodium butyrate (SB), granulocyte-macrophage colony-stimulating factor (GM-CSF), and other differentiating agents. U937-C361 differentiation correlated with increased cellular luciferase levels, showing the inducibility of the CD11c promoter during myeloid differentiation and establishing the U937-C361 cells as a suitable system for studying the myeloid differentiation-inducing capacity of cytokines, growth, factors, and other biological response modifiers. Unexpectedly, the inducibility of the CD11c gene promoter showed distinct kinetics and magnitude on the PMA-, SB-, GM-CSF-triggered differentiation. Moreover, SB synergized with either PMA or GM-CSF in enhancing both the CD11c promoter activity and the cell surface expression of p150,95 on differentiating U937 cells. Furthermore, we showed the existence of a c-Myb-binding site at -85, the importance of the -99/-61 region in the CD11c promoter inducibility during PMA- or SB-triggered differentiation, and the dependency of the GM-CSF and PMA responsiveness of the CD11c promoter on an intact AP-1-binding site located at -60. These results, together with the lack of functional effect of mutations disrupting the Sp1-and Myb-binding sites within the proximal region of the CD11c promoter, indicate that the myeloid differentiation pathways indicated by SB and phorbol esters (or GM-CSF) activate a distinct set of transcription factors and show that the myeloid differentiation-inducibility of the CD11c gene maps to the -99/-53 proximal region of the promoter.

Base Sequence↗
PubMed1993

Periodontal diseases in young individuals.

The prevalence and severity of periodontal diseases in young people are significant. Recent progress in understanding the etiology and pathogenesis of periodontal diseases in this group of patients has allowed significant improvement in periodontal classifications. Actinobacillus actinomycetemcomitans characteristically is the major pathogen involved; black-pigmented anaerobic rods and other organisms can also be important. Treatment of periodontitis should focus on meticulous plaque control and eradication of periodontal pathogens, possibly by means of systemic or topical antimicrobial therapies.

Adolescent↗
PubMed1995

Antigen-driven induction of CD11c on intestinal intraepithelial lymphocytes and CD8+ T cells in vivo.

Intraepithelial lymphocytes (IEL) of the intestinal epithelium represent a phenotypically and functionally distinct subpopulation of peripheral T cells. In this study, we report the production of a mAb, designated HL3, which exhibits reactivity with a subset of IEL. In differential screening assays HL3 reacted with 30 to 50% of IEL, but not with T cells of the thymus, spleen, or lymph nodes. Biochemical characterization revealed that the HL3 mAb recognized p150,95 (CD11c/CD18; CR4), a member of the beta 2-integrin family. Fluorescence flow cytometric analyses showed that p150,95 was expressed by TCR-alpha beta or TCR-gamma delta CD4-8+ IEL but not by CD4+8- IEL. Induction of graft-vs-host (GVH) disease resulted in up-regulation of p150,95 expression on donor-derived CD8+ T cells in the intestinal epithelium, as well as in the spleen and lymph nodes. GVH also induced MAC-1 (CD11b) expression on a subset of CD8+ lymph node T cells, but MAC-1 was not up-regulated on CD8+ IEL in this situation. In contrast, activation of identical T cell responders in vitro resulted in weak induction of p150,95 and MAC-1 expression. This result suggested that activation alone was insufficient for p150,95 up-regulation and that additional factors available in vivo were essential in this process. In the intestine, induction of p150,95 required the presence of intestinal flora as IEL from germfree mice lacked p150,95. Interestingly, gamma delta IEL expressing a non-IEL type transgenic TCR were also p150,95-, but exposure to Ag in vivo, but not in vitro, resulted in p150,95 induction. This result indicated that the constitutive expression of p150,95 on IEL is likely due to Ag stimulation via the TCR and not a bystander phenomenon. Overall, the results demonstrated p150,95 to be a hallmark of T cell activation in vivo and an indicator of ongoing antigen-specific T cell activation in the intestinal epithelium.

Animals↗
PubMedDate not supplied

CD11c expression in B-cell chronic lymphocytic leukemia. A comparison of results obtained with different monoclonal antibodies.

In order to obtain more information on the pattern of CD11c-positivity in otherwise typical B-cell chronic lymphocytic leukemia (CLL), we analyzed immunological and clinico-pathological features of 99 such patients studied with two different monoclonal antibodies (MoAbs). Fifty-two out of 70 (74.2%) patients stained with IOM-11C MoAb and 3 out of 29 (10.3%) patients stained with Leu-M5 MoAb had more than 30% CD11c positive cells (P < 0.0002). The two groups were similar with regard to the expression of B-cell CLL-related antigens (CD5, CD20, CD23), as well as clinico-pathological features (i.e. Binet clinical stage and pattern of bone marrow involvement), thus suggesting that differences in CD11c expression were due to different reactivity patterns of the MoAbs utilized. In our experience, the use of different reagents may affect immunophenotyping results, thus providing conflicting data at times.

Aged↗
PubMed1994

Bovine C4b binding protein. Molecular cloning of the alpha- and beta-chains provides structural background for lack of complex formation with protein S.

C4b binding protein (C4BP) regulates the complement system. It also interacts with anticoagulant protein S and with serum amyloid P component. Human C4BP is composed of seven identical 70-kDa alpha-chains and one 45-kDa beta-chain. The binding site for C4b is located on the alpha-chain, whereas the beta-chain binds protein S. Nothing is known about the structure and function of bovine C4BP. No complexed form of protein S was detected by using a gel filtration chromatography system combined with Western blotting. Bovine cDNA clones encoding the C4BP alpha- and beta-chains were isolated from a bovine liver cDNA library. Three overlapping alpha-chain clones predicted a 562-amino acid residues-long mature polypeptide. The overall amino acid sequence similarity with the human alpha-chain was 61%. Like its human counterpart, the bovine alpha-chain is composed of eight contiguous short consensus repeat units, each of approximately 60 amino acid residues, and a carboxyl-terminal nonrepeat region. One bovine beta-chain clone was found and characterized. It predicted a mature bovine beta-chain of 181 amino acid residues. The identity with the human beta-chain was 65% at the amino acid level. A noteworthy difference between bovine and human beta-chains was that the bovine beta-chain only contained two short consensus repeats compared with three in human beta-chain. Sequence alignment indicates that the region corresponding to residues 1-60 (repeat 1) in the human beta-chain is absent in the homologous bovine polypeptide. Because the short consensus repeats of the human beta-chain contain the binding site for protein S, the lack of one repeat unit in the bovine beta-chain may provide a clue to the lack of complex formation between C4BP and protein S in bovine plasma.

Amino Acid Sequence↗
PubMed1995

Ig-binding surface proteins of Streptococcus pyogenes also bind human C4b-binding protein (C4BP), a regulatory component of the complement system.

Streptococcus pyogenes, an important human pathogen, expresses several proteins that interact with the immune system of the host. Among the proteins isolated from different bacterial strains are antiphagocytic M proteins, Ig Fc-binding proteins and exotoxins that act as superantigens. Here we report a novel interaction between S. pyogenes and the human immune system, the ability of most S. pyogenes strains to bind human C4BP (C4b-binding protein), a 570-kDa serum protein that inhibits the classical pathway of complement activation. Molecular analysis of three different streptococcal strains demonstrated that C4BP binds to protein Arp or protein Sir, two Ig-binding cell surface molecules that are members of the M protein family. These bacterial proteins have separate high affinity binding sites for Ig and for C4BP, as demonstrated by inhibition tests and binding assays with purified components. A single streptococcal cell surface molecule, Arp or Sir, therefore combines the abilities to bind Ig and C4BP, two high m.w. components of the immune system. Two bacterial strains expressing Arp or Sir were shown to selectively bind C4BP in whole human serum, suggesting that S. pyogenes also binds C4BP in the infected host. When bound to streptococcal cells, C4BP retained its ability to act as a cofactor in the degradation of C4b by factor I. These results indicate that many strains of S. pyogenes interfere with the classical pathway of complement activation by binding C4BP to the bacterial cell surface.

Antigens, Bacterial↗
PubMed1994

Human protein S inhibits prothrombinase complex activity on endothelial cells and platelets via direct interactions with factors Va and Xa.

Protein S is a vitamin K-dependent non-enzymatic coagulation factor involved in the regulation of activated protein C (APC). In this paper we report an APC-independent anticoagulant function of protein S. We observed an inhibition of prothrombinase activity on endothelial cells and platelets which was half-maximal at physiological concentrations of free protein S in plasma. On endothelial cells, thrombin-cleaved protein S (PSt) as well as protein S in complex with C4b-binding protein (C4BP) inhibited prothrombinase activity to the same extent as protein S did. In solid-phase binding assays, direct binding of protein S and PSt to factor V and factor Va were observed. Protein S-C4BP complex did not bind to factor V or factor Va, implicating that the factor V(a) binding site on protein S is lost by the interaction with C4BP. A direct inhibition of factor Xa activity by protein S was also observed. Incubation of factor Xa with protein S revealed a noncompetitive inhibition of factor Xa by protein S with a Ki of (4.9 +/- 0.8) x 10(-7) M. Both protein S and protein S-C4BP complex were able to inhibit factor Xa to the same extent, whereas PSt had lost its inhibitory activity. This suggests that the conformational change induced by cleavage of the amino-terminal thrombin-sensitive loop results in a loss of a factor Xa binding site on protein S. The inhibitory effect of protein S involves interactions with both factor Va and factor Xa. The interaction of protein S with factor Xa is influenced by cleavage of the thrombin-sensitive loop, whereas C4BP blocks the interaction of protein S with factor Va. Inhibition of the prothrombinase complex by either forms of protein S might be an important mechanism in regulating thrombin generation in blood coagulation. The importance of the APC-independent anticoagulant action of protein S was emphasized by experiments in which the addition of protein S to normal plasma induced a prolongation of clotting time in a dilute activated partial thromboplastin time (dAPTT) assay. Furthermore, inhibition of endogenous protein S by the addition of monoclonal antibodies against protein S to normal plasma, induced a shortening of the clotting time in a dAPTT assay.

Blood Platelets↗
PubMed1993

U937 cell line: impact of CSFs, IL-6 and IFN-gamma on the differentiation and the Leu-CAM proteins expression.

Differentiation of the U937 cell line can be induced by various agents. We have investigated the differentiation abilities of gamma-interferon (IFN-gamma), interleukin-6 (IL-6), macrophage and granulocyte-macrophage colony-stimulating factors (M-CSF + GM-CSF) or the combinations IL-6 + M-CSF + GM-CSF and IFN-gamma + M-CSF + GM-CSF on the U937 cells by studying the morphology, cytochemical activity and several functional properties. The expression of the Leu-CAM proteins (CD11a, CD11b, CD11c, CD18) was also evaluated during the culture period. Our results show that the cytokines used in this study inhibit to a certain extent the proliferation of the tumor cells and drive the cells toward a differentiation phenotype that has several characteristics in common with mononuclear phagocytes, such as the expression of CD14, phagocytosis and release of superoxide anions. The adhesion molecules CD11b alpha chain and CD18 beta chain were strongly induced on the U937 cells with a maximal expression of the CD11b on the cells cultured with either M-CSF + GM-CSF or the combinations of IL-6 and IFN-gamma with M-CSF + GM-CSF. Conversely, for CD11a and CD11c alpha chains a rather low enhancement of the expression was noticed. In our culture system, cells incubated with the combination of M-CSF + GM-CSF exhibited differentiation characteristics which appeared to be largely potentialized when cytokines such as IL-6 or IFN-gamma were added.

Antigens, CD↗
PubMed1993

Protein S Tokushima: an abnormal protein S found in a Japanese family with thrombosis.

An abnormal protein S (PS) was found in a Japanese family with a high incidence of thrombosis. The proband is a woman who was born in Tokushima Prefecture. She had superior sagittal sinus thrombosis, thrombophlebitis of the left leg, and thrombosis of the placenta. She had a normal plasma level of free PS antigen but decreased PS activity. Her mother and aunt also had thrombophlebitis of the leg, and together with four other family members also showed a normal level but decreased activity of PS. This suggests that hereditary dysfunction of PS is inherited in this family as an autosomal dominant trait. The proband's PS appears to have a slightly higher molecular weight than normal PS both in the intact and modified form, suggesting that it has a molecular defect on the carboxyl-terminal side of the thrombin-sensitive site. This abnormal PS with apparently unique characteristics was named PS Tokushima.

Adult↗
PubMed1993

Ventral dermatitis and vasculitis in a calf with bovine leukocyte adhesion deficiency.

Dermatitis and vasculitis of the skin covering the sternum of a calf with bovine leukocyte adhesion deficiency was observed. The calf had been conceived through artificial insemination, delivered by cesarean section, and placed in a gnotobiotic isolator. Dermatitis was noticed at 54 days of age and was not responsive to antibiotic or ivermectin treatment. Proteus sp, Enterobacter sp, and Candida tropicalis were isolated from skin specimens. The lesion was characterized by lymphoplasmacytic and histiocytic inflammation with vasculitis and thrombosis.

Animals↗
PubMed1996

Expression of the p53 tumor suppressor gene induces differentiation and promotes induction of differentiation by 1,25-dihydroxycholecalciferol in leukemic U-937 cells.

Leukemic U-937 cells, which lack normal p53, were stably transfected with a temperature-sensitive mutant of p53 to investigate the consequences for growth and differentiation. On induction of wild-type p53 activity at the permissive temperature, some of these cells underwent maturation as judged by the capacity for oxidative burst and the appearance of monocyte related cell surface molecules. Moreover, wild-type p53-expressing cells were more sensitive than p53-negative control cells to induction of differentiation by 1,25-dihydroxycholecalciferol; a twofold to fourfold increase of the fraction of cells showing signs of terminal maturation was observed when wild-type p53-expressing cells were incubated with 1,25-dihydroxycholecalciferol at concentrations that only slightly affected control cells. Whereas wild-type p53 activity per se induced maturation of certain cells, other underwent cell death judging from the reduced capability to exclude trypan blue and the appearance of fragmented DNA in flow cytometric analysis. The p53-induced cell death could be inhibited by incubation with 1,25-dihydroxy-cholecalciferol, but not all-trans retinoic acid. Thus, 1,25-dihydroxycholecalciferol, seemed to increase the survival of wild-type p53-expressing cells and to cooperate with wild-type p53 to induce differentiation. The data imply that p53-mediated maturation in U-937 cells depends on optimal regulation of signals for differentiation, survival and proliferation, and suggest a role for p53 in the differentiation induction of leukemic cells.

Apoptosis↗
PubMed1996

AP-1 regulates the basal and developmentally induced transcription of the CD11c leukocyte integrin gene.

The p150,95 integrin (CD11c/CD18) mediates leukocyte/endothelium interactions during inflammatory reactions and certain CTL-target interactions, and is also a receptor for fibrinogen, LPS, and the complement component iC3b. CD11c/CD18 is expressed primarily on cells of the myeloid lineage and activated B lymphocytes, and is an important diagnostic marker for hairy cell leukemia. To identify the transcription factors and cis-acting elements involved in the regulated expression of CD11c/CD18 during myeloid cell differentiation and B lymphocyte activation, we have performed structural and functional analysis on the CD11c gene promoter. Electrophoretic mobility shift assays identified an AP-1 binding site (AP1-60) within the proximal promoter region and evidenced differences in the pattern of the Fos family members bound to the AP1-60 element in undifferentiated and differentiated myeloid cells, as well as between B lineage-derived cells. The involvement of the AP1-60 element in DNA-protein interactions was confirmed by means of in vivo footprinting experiments, and its functionality was demonstrated by trans activation of the CD11c promoter by c-Jun. Site-directed mutagenesis of AP1-60 greatly reduced the basal CD11c promoter activity in myeloid and B cells. Furthermore, mutations at AP1-60 inhibited the induction of the CD11c promoter activity during the PMA-triggered U937 cell differentiation, pointing out a key role for the AP-1 transcription factor complex in both the basal and the developmentally regulated expression of the p150,95 leukocyte integrin. The involvement of AP-1 in the transcription of the CD11c gene raises the possibility of altering leukocyte integrin expression by pharmacologic means and will greatly contribute to the characterization of the intracellular signals controlling the expression of leukocyte adhesion molecules.

Base Sequence↗
PubMed1996

A highly variable region in members of the streptococcal M protein family binds the human complement regulator C4BP.

Strains of Streptococcus pyogenes express one or more molecules that are members of the M protein family, a group of surface proteins implicated in virulence. A characteristic property of the molecules in this family is the presence of a highly variable N-terminal region, whose function is unknown. Here we show that human C4b-binding protein (C4BP), a regulatory component of the complement system, binds to the highly variable region of many members of the M protein family. Chimeric molecules, in which the N-terminal regions of four different C4BP-binding proteins were combined with the C-terminal part of the non-binding M5 protein, had intact C4BP-binding ability, as judged by binding assays and Scatchard analysis with highly purified molecules. Moreover, work with the C4BP-binding Arp4 protein showed that an N-terminal 52-residue fragment retained binding ability, and that a 21-residue synthetic peptide derived from the variable region completely inhibited the binding of C4BP. Computer-assisted analysis of the four C4BP-binding regions studied here (45-66 amino acid residues) indicated that they lack residue identities that could explain their ability to bind the same ligand, but differ from the nonbinding M5 protein in their lower propensity to form a coiled-coil. Thus, the variable C4BP-binding regions have an extraordinary capacity for sequence variation, while retaining the ability to bind C4BP. These data indicate that an important function of the variable region in members of the M protein family is to bind a host protein that down-regulates the complement system.

Amino Acid Sequence↗