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PubMed2000

Adsorbed serum proteins responsible for surface dependent human macrophage behavior.

Substrate specific cellular responses are the result of a complex biological system that includes protein adsorption, receptor-ligand binding, and signal transduction. This investigation attempted to identify specific proteins adsorbed from human serum that may be responsible for the previously reported in vitro surface dependent behavior of human macrophages and foreign body giant cells (FBGCs). The adsorption of human albumin, alpha(2)-macroglobulin, complement factor 3b, fibronectin, IgG, thrombospondin, vitronectin (VN), and von Willebrand factor (vWF) from a 25% serum solution was quantified with (125)I-labeled protein. Adsorption substrates included clean glass, alkyl-silane modified glass, amino-silane modified glass, poly(ethylene oxide) (PEO)-coupled glass, and the reference biomaterials poly(etherurethane urea), Silastic(R), and poly(tetrafluoroethylene) (PTFE). Following quantification of 2-h adsorption, surfaces were treated with sodium dodecyl sulfate (SDS) and the level of adsorbed proteins remaining was quantified. The pre- and post-SDS adsorption were both compared to previously reported surface dependent in vitro macrophage and FBGC behavior on the same surfaces; however, no correlations could be made. Adsorption strength, defined as the percentage of initially adsorbed protein that remained adsorbed after SDS treatment, correlated well with previously reported in vitro cellular behavior indicating that adsorbed vWF, IgG, and VN may be involved in the modulation of adherent macrophage and FBGC behavior. Those surfaces that strongly adsorbed vWF also inhibited long-term macrophage adhesion, while those surfaces that strongly adsorbed IgG promoted long-term macrophage adhesion. In addition, the highest levels of FBGC formation had been observed only on those surfaces that strongly adsorbed VN. Subsequent human monocyte cultures on protein preadsorbed substrates confirmed the inhibitory effect of adsorbed vWF and the promoting effect of IgG on longterm macrophage adhesion as predicted by adsorption strength correlations. However, preadsorbed VN was not observed to modulate FBGC formation, which is in contrast to the conclusions of the adsorption correlations.

Adsorption↗
PubMed1991

Characterization of the rat leukocyte integrin, CD11/CD18, by the use of LFA-1 subunit-specific monoclonal antibodies.

We have attempted to characterize the rat leukocyte integrin, CD11/CD18, by the use of newly generated monoclonal antibodies (mAb) WT.1 (anti-CD11a) and WT.3 (anti-CD18) in conjunction with an mAb, OX42, reactive with a rat integrin-like molecule, with respect to the biochemistry, cellular distribution and function. The conclusion that the mAb WT.1 and WT.3 specifically recognize the rat CD11a and CD18, respectively, was based on: (a) their ability to inhibit homotypic aggregation of splenic concanavalin A (Con A) blasts; (b) sodium dodecyl sulfate-polyacrylamide gel electrophoretic analysis of the antigens recognized; (c) their ability to inhibit binding of Con A blasts to the purified ligand, namely the ICAM-1 antigen and (d) their blocking abilities in mixed leukocyte reaction. In the rat, CD18 has an apparent molecular mass of 95-100 kDa and can associate with at least three distinct alpha subunits of 160-170 kDa (CD11a), 140-150 kDa and 120-130 kDa. The latter two are precipitated by OX42 from M phi but not from unstimulated lymphocytes. They presumably represent the rat CD11b and CD11c, respectively. Rat thymocytes, PBL, thoracic duct lymphocytes, monocytes and neutrophils expressed differential levels of CD11a and CD18. Peritoneal M phi showed virtually no CD11a expression, although CD18 was expressed at levels similar to those seen on blood monocytes, showing an interesting pattern of LFA-1 expression regulation in this cell lineage. Both WT.1 (anti-CD11a) and WT.3 (anti-CD18) apparently recognize a "low-affinity" as well as a "high-affinity" form of LFA-1 and do not discriminate between the two.

Animals↗
PubMed1992

Tissue-specific and allelic expression of the complement regulator CD46 is controlled by alternative splicing.

CD46 (membrane cofactor protein) is a human cell surface glycoprotein with cofactor activity for factor I-mediated cleavage of complement components C3b and C4b. The CD46 protein from normal lymphocytes resolves on sodium dodecyl sulfate-polyacrylamide gel electrophoresis as two major bands of 66 and 56 kDa. CD46 cDNA encodes four extracellular short consensus repeat domains, a Ser/Thr/Pro (STP)-rich region, a transmembrane region and a cytoplasmic tail. We now show that exquisite control of mRNA splicing is responsible for the heterogeneous expression of CD46 isoforms. Differential splicing of 5 exons generates at least 14 CD46 mRNA variants whose expression is stringently regulated by allelic, tissue-specific and malignancy-related factors, as: (a) leukemic cells and Epstein-Barr virus-transformed B cells preferentially incorporate the first of three STP exons (exon 7) into mRNA, and produce a larger CD46 isoform of 74 kDa, (b) an allelic difference in the proportion of 66- and 56-kDa CD46 isoforms on lymphocytes corresponds to the preferential inclusion or exclusion of the second STP exon (exon 8), (c) the third STP exon (exon 9) is specifically deleted in some placentae, (d) spermatozoa delete both exons 12 and 13, encoding a shorter transmembrane region and a unique cytoplasmic tail and (e) all tissues tested differentially splice exon 13, resulting in two alternative cytoplasmic tails. The distribution of the 14 alternatively spliced RNA transcripts correlated with the presence of protein isoforms of the predicted size, indicating that alternative splicing leads to heterogeneity of CD46 glycoproteins.

Alleles↗
PubMed1993

KIM185, a monoclonal antibody to CD18 which induces a change in the conformation of CD18 and promotes both LFA-1- and CR3-dependent adhesion.

Unactivated peripheral blood leukocytes show little tendency to bind to other cells or matrix components, whilst, in the presence of inflammatory mediators, adhesive interactions can rapidly increase. The Leu-CAM (beta 2 integrin) family of adhesion molecules have been shown to mediate a variety of these induced adhesion events. Here we describe a monoclonal antibody against CD18, KIM185, which stimulates JY cell homotypic aggregation by a CD11 a pathway as well as inducing the adherence of neutrophils to protein-coated plastic by a CD11b-dependent mechanism. The antibody recognizes an epitope distinct from the previously described KIM127 antibody and evidence is presented that the binding of KIM185 can cause a change in the conformation of the CD18 molecule.

Antibodies, Monoclonal↗
PubMed2004

An interaction between CD16 and CR3 enhances iC3b binding to CR3 but is lost during differentiation of monocytes into dendritic cells.

The receptor for the iC3b fragment of complement, CR3, is involved in monocytes/macrophages and neutrophils phagocytosis. CR3 is known to interact with the low affinity receptor for Ig (CD16) and previous studies have suggested that this cooperation modulates CR3 functions. Herein we have studied the effect of CD16 on the ability of human monocytes CR3 to bind to iC3b. We show that iC3b binding to CR3 is inhibited by several reagents that are known to dissociate the CD16/CR3 complex. In addition, treatment of monocytes with soluble CD16 inhibited iC3b binding to CR3. Together, these data indicate that iC3b binding to monocyte CR3 is up-regulated by an interaction between membrane CD16 and CR3. The implication of CD16 in CR3 binding to iC3b was also analyzed after monocyte differentiation into dendritic cells (DC). Differentiation of monocytes into DC abrogates the cooperation between CD16 and CR3, due to a loss of CD16/CR3 interaction. In accordance, this phenomenon is associated with a lack of iC3b binding to DC. As a consequence, deposition of iC3b on apoptotic cells does not modify their phagocytosis by DC. In conclusion, we demonstrate a cooperation between CD16 and CR3 that favors iC3b binding to CR3 but is lost on DC.

Apoptosis↗
PubMed1996

Inhibition and stimulation of LFA-1 and Mac-1 functions by antibodies against murine CD18. Evidence that the LFA-1 binding sites for ICAM-1, -2, and -3 are distinct.

The murine CD18 monoclonal antibody (mAb) M18/2 was reported to inhibit lymphoma metastasis [Zahalka, M. A. et al. (1993) J. Immunol. 150, 4466]. To identify the pathways potentially blocked, we studied the effects of M18/2 compared with two new mAb against murine CD18, GAME-46, and -245. Whereas the GAME mAb blocked most Mac-1-mediated interactions, M18/2 had no effect, or even stimulated. The same was true for adhesion of LFA-1 to ICAM-1. To test effects on interactions with different ICAMs, we used L cells transfected with human ICAM-1, -2, and -3. As previously described, mouse LFA-1 does not bind to human ICAM-1 but we show here that mouse LFA-1 does bind to human ICAM-2 and -3. Again, the GAME mAb blocked completely, but M18/2 did not. These results indicate that the LFA-1 binding sites for ICAM-1 and ICAM-2 and -3, although in close vicinity, are distinct. Furthermore, effects of M18/2 on metastasis cannot be ascribed to blocking of any known beta2-integrin activity.

Animals↗
PubMed1998

Expression of a structural domain of the beta 2 subunit essential for alpha M beta 2 ligand recognition.

The beta2 leukocyte integrins comprise a group of closely related adhesion receptors that mediate critical events during normal and inflammatory immune responses. Central to the understanding of beta2 integrin function is the basis of ligand recognition. Results from our laboratory and others indicate the presence of multiple ligand contact points in both the alpha and beta subunit. As an approach to identify and characterize regulatory domains of the beta2 subunit, we have generated two different subdomains of the beta2 subunit for expression on the surface of mammalian cells through a phosphatidyl-inositol glycan anchor. The first subdomain contains the putative beta2 MIDAS motif implicated in ligand binding [beta2(LB)], whereas the second beta2 subdomain contains the cysteine-rich region [beta2(CR)]. Cells expressing alphaM and beta2 constructs singly or cotransfected transiently in COS-7 cells were tested for the ability to bind to immobilized iC3b. Cells bearing the recombinant alphaMbeta2(LB) were capable of adhering to iC3b in a manner similar to that observed with the complete alphaMbeta2 heterodimer. In contrast, cells expressing alphaMbeta2(CR) failed to adhere to immobilized iC3b. Moreover, cells bearing singly transfected alpha or beta chains alone failed to adhere to immobilized iC3b. These results indicate that along with alphaM, the beta2(LB) subdomain contains the sufficient components within the beta2 subunit essential for ligand recognition. These findings support the hypothesis that the beta2 subunit cooperates with site(s) within the alphaM subunit in a receptor/cation/ligand complex resulting in high-affinity ligand interaction.

Animals↗
PubMed1999

Localization of p21-activated kinase 1 (PAK1) to pseudopodia, membrane ruffles, and phagocytic cups in activated human neutrophils.

Leukocyte chemoattractants are known to stimulate signaling pathways that involve Rho family GTPases. Direct evidence for the regulation of the leukocyte cytoskeleton by Rho GTPases and their effector targets is limited. The p21-activated kinases (PAKs) are specific targets of activated GTP-bound Rac and Cdc42, and have been proposed as regulators of chemoattractant-driven actin cytoskeletal changes in fibroblasts. PAK1 colocalizes with F-actin to cortical actin structures in stimulated fibroblasts, and activated PAK1 mutants induce membrane ruffling and polarized cytoskeletal rearrangements. We investigated whether PAK1 was associated with remodeling of the actin cytoskeleton in activated human neutrophils. We monitored the redistribution of PAK1 and F-actin into the actin cytoskeleton after stimulation of human neutrophils with the chemoattractant N-formyl-methionyl-leucyl-phenylalanine (fMLP) or the particulate stimulus, opsonized zymosan (OZ). PAK1 exhibited a similar distribution as F-actin in fMLP-stimulated leukocytes, localizing in membrane ruffles and to lamellipodia at the leading edge of polarized cells. Addition of OZ induced phagocytic uptake of this particulate stimulus, and PAK1 re-localized to the F-actin-rich pseudopodia and phagocytic cups associated with this process. Once the OZ was internalized, there was little PAK1 localized around the ingested particles, suggesting that PAK1 may be regulating the cytoskeletal extensions and events required for engulfment of bacteria, but not the subsequent steps of internalization. Localization of PAK1 and F-actin in cytoskeletal structures was abolished by the actin polymerization inhibitor cytochalasin D and the phosphatidylinositol 3-kinase inhibitor wortmannin. Our data suggest that PAK1 may regulate a subset of cytoskeletal dynamics initiated by chemoattractant and phagocytic stimuli in human neutrophils.

Actins↗
PubMed1993

Differentiation of conglutination activity and sugar-binding activity of conglutinin after removal of NH2-terminal 54 amino acid residues by endogenous serine protease(s).

Bovine conglutinin, which is a serum lectin specific for N-acetylglucosamine, was purified from heat-inactivated bovine serum by Sepharose 4B-mannan affinity chromatography. Without prior heat inactivation, however, the same affinity chromatography yielded a modified conglutinin, which retained sugar-binding, but not conglutination activity. The modified lectin was designated conglutinin-N. The conglutinin-N subunit (38 kDa) was smaller than that of conglutinin (45 kDa). The apparent molecular mass was also reduced from 1000 (conglutinin) to 600 kDa (conglutinin-N). Conglutinin-N and conglutinin reacted equally with a rabbit anti-conglutinin antiserum. Comparison of the NH2-terminal sequences of conglutinin-N with the primary structure of conglutinin [Lee, Y-M., Leiby, K. R. Allar, J., Paris, K., Lerch, B., and Okarma, T. B. (1991) J. Biol. Chem. 266, 2715-2723] revealed that the removal of the 54 NH2-terminal amino acids of conglutinin produced conglutinin-N. This conversion of conglutinin to conglutinin-N was catalyzed by the eluate fraction of the first affinity chromatography from untreated bovine serum and was inhibited by serine protease inhibitors such as [4-aminophenyl]methanesulfonyl fluoride and C1 inhibitor. Conglutinin-N had neither conglutination activity nor binding activity to the sensitized erythrocyte-solid phase iC3b complex (EAiC3b), although it retained the binding activity to mannan in solution and the original binding specificity for N-acetylglucosamine. Cross-linking showed that conglutinin-N formed trimers of the 38-kDa subunits, whereas conglutinin formed higher multimers of 9-18 mer. These results indicated that deleting the NH2-terminal portion containing three cysteine residues by endogenous serine protease(s) produced some conformational changes in the entire molecule, which resulted in the loss of binding activity to EAiC3b and retention of the sugar-binding property.

Amino Acid Sequence↗
PubMed1993

Complement component C3-derived neutrophil chemotactic factors purified from exudate of rat carrageenin-induced inflammation.

Two neutrophil chemotactic factors have been purified from the exudate of chronic-phase of rat carrageenin-induced inflammation. Both the factors were derived from the third component of complement (C3); one was an NH2-terminal fragment (C3a) of alpha chain of C3 and another chemoattractant was a COOH-terminal fragment of beta chain, which was referred to as C3 beta c, on the basis of their molecular masses and NH2-terminal amino acid sequences. C3a exhibits potent chemotactic activity for rat neutrophils, and C3 beta c is a novel basic neutrophil chemoattractant with molecular mass of about 11 kDa, suggesting that both chemoattractants play a role in the neutrophil infiltration into inflammatory site of carrageenin-induced inflammation in rats.

Amino Acid Sequence↗
PubMed1996

Expression of the carbohydrate recognition domain of bovine conglutinin and demonstration of its binding to iC3b and yeast mannan.

Bovine conglutinin is a collagenous C-type lectin (collectin) that is found in bovine serum. A recombinant protein, composed of the neck-region and the carbohydrate binding domain of bovine conglutinin, has been overexpressed in E. coli. The recombinant protein has been successfully renatured and showed the same sugar binding specificity as the native protein and was able to bind to yeast mannan and complement-activated immune complexes. The binding was calcium-dependent and was inhibited by N-acetylglucosamine. The concentration of N-acetylglucosamine required for 50% inhibition of binding to mannan was 1.77 mM for recombinant conglutinin and 0.71 mM for native conglutinin, respectively. The recombinant conglutinin should be useful in the assay and purification of circulating immune complexes and for therapeutic purposes involving the removal of immune complexes from patient's plasma.

Acetylglucosamine↗
PubMed1998

Purification from human plasma of a hexapeptide that potentiates the sulfation and mitogenic activities of insulin-like growth factors.

The human plasma contains small peptide molecules known as low molecular weight growth factors synergistically increasing certain biological actions of insulin-like growth factors. In the present work we isolated and characterized a hexapeptide with HWESAS as structure. This purified peptide was absolutely necessary for the sulfation activity of insulin-like growth factor-I on chick embryo pelvic cartilages and improved the mitogenic activity of both insulin-like growth factors. The effects of this hexapeptide were confirmed by using the homologous synthetic peptide, that exhibited similar biological effects. Other synthetic peptides with structure derived from hexapeptide were shown to be active: the pentapeptide HWESA appeared more potent than the tripeptide HWE, which is about 170 to 200 times less active than the hexapeptide. The sequence of hexapeptide HWESAS is identified in only one human protein that is C3f, a fragment of C3 complement.

Animals↗
PubMed1998

Acute inflammatory response in spinal cord following impact injury.

Numerous factors are involved in the spread of secondary damage in spinal cord after traumatic injury, including ischemia, edema, increased excitatory amino acids, and oxidative damage to the tissue from reactive oxygen species. Neutrophils and macrophages can produce reactive oxygen species when activated and thus may contribute to the lipid peroxidation that is known to occur after spinal cord injury. This study examined the rostral-caudal distribution of neutrophils and macrophages/microglia at 4, 6, 24, and 48 h after contusion injury to the T10 spinal cord of rat (10 g weight, 50 mm drop). Neutrophils were located predominantly in necrotic regions, with a time course that peaked at 24 h as measured with assays of myeloperoxidase activity (MPO). The sharpest peak of MPO activity was localized between 4 mm rostral and caudal to the injury. Macrophages/microglia were visualized with antibodies against ED1 and OX-42. Numerous cells with a phagocytic morphology were present by 24 h, with a higher number by 48 h. These cells were predominantly located within the gray matter and dorsal funiculus white matter. The number of cells gradually declined through 6 mm rostral and caudal to the lesion. OX-42 staining also revealed reactive microglia with blunt processes, particularly at levels distant to the lesion. The number of macrophages/microglia was significantly correlated with the amount of tissue damage at each level. Treatments to decrease the inflammatory response are likely to be beneficial to recovery of function after traumatic spinal cord injury.

Animals↗
PubMed1998

Intrastriatal transplantation of rat adrenal chromaffin cells seeded on microcarrier beads promote long-term functional recovery in hemiparkinsonian rats.

Possible biologic treatments for Parkinson's disease, a disorder caused by the deterioration of dopaminergic neurons bridging the nigrostriatal system, have recently focused on fetal cell transplantation. Because of ethical and tissue availability issues concerning fetal cell transplantation, alternative cell sources are being developed. The adrenal medulla has been used as a cell transplant source because of the capacity of the cells to provide catecholamines and to transform into a neuronal phenotype. However, adrenal tissue transplants have shown limited success, primarily because of their lack of long-term viability. Recently, seeding adrenal chromaffin cells on microcarrier beads has been shown to enhance the cell viability following neural transplantation. In the present study, we further investigated whether transplantation of rat adrenal chromaffin cells seeded on microcarrier beads into the striatum of 6-hydroxydopamine-induced hemiparkinsonian rats would result in a sustained functional recovery. Behavioral tests using the apomorphine-induced rotational and elevated body swing tests up to 12 months posttransplantation revealed a significant behavioral recovery in animals that received adrenal chromaffin cells seeded on microcarrier beads compared to animals that received adrenal chromaffin cells alone, medium alone, or beads alone. Histological examination of tissue at 14 months posttransplantation revealed evidence of tyrosine hydroxylase-positive cells and an on-going glial response in animals transplanted with adrenal chromaffin cells seeded on microcarrier beads, in contrast to absence of such immunoreactive responses in the other groups. These findings support a facilitator role for microcarrier beads in transplantation of adrenal chromaffin cells or other cells that are easily rejected by the CNS.

Adrenal Glands↗
PubMed1989

Comparative studies on the adhesiveness of granulocytes of guinea pig and man.

The high affinity of granulocytes of guinea pig and man to glass surfaces is modified by serum. Native serum contains both an adherence-promoting activity, which is related to complement, and components which reduce the adhesiveness of granulocytes. These components are stable at 56 degrees C for 30 min and are tightly bound to the glass surface. beta-Lipoproteins are candidates for this adherence reducing ability of serum. Adherence promotion by native serum is mediated by coating the glass surface with C3b/C3bi. Human granulocytes from the peripheral blood adhered pig serum with C3b/C3bi to almost the same extent as in the presence of native serum, but on guinea pig granulocytes elicited in the peritoneal cavity, a cell surface metalloproteinase degraded the C3b/C3bi, thus reducing the adhesiveness of these cells. This proteinase was inhibited by MgEDTA, DTT, and 1,10-phenanthroline, whereby the high adhesiveness of granulocytes was restored to C3b/C3bi-coated glass.

Animals↗
PubMed1983

Human dendritic reticulum cells of lymphoid follicles: their antigenic profile and their identification as multinucleated giant cells.

The B-dependent areas of human lymphoid tissue contain non-lymphoid, non-phagocytic cells known as dendritic reticulum cells (DRC). These cells can be detected only very occasionally in routinely stained histologic sections. Recently we were able to overcome this limitation by preparing a monoclonal antibody, termed R 4/23, that reacts selectively with DRC. Thus by using an optimized immunoperoxidase method applied to frozen sections, it is possible to detect DRC in situ. To determine the antigenic profile of DRC, serial frozen sections of human tonsils were immunostained with R 4/23 and a large panel of other monoclonal antibodies or conventional antisera. In addition, touch imprints of tonsils and cytocentrifuge slides of cell suspensions with increased concentrations of DRC were immunostained with these reagents. DRC proved to be positive for mu, gamma, alpha, kappa and lambda chains, complement component C3b, C3b receptors, C3d receptors, HLA-A,B,C antigens, human Ia-like antigens, common ALL antigen (cALLa), and antigens that are characteristic of the monocyte/macrophage lineages. DRC did not express delta chains, T cell antigens, or antigens that are expressed on interdigitating reticulum cells (IDC) and Langerhans cells. DRC in touch imprints and suspensions prepared from hyperplastic tonsils were found to be giant cells often with 10 or more nuclei. In certain cases of follicular hyperplasia and of centroblastic-centrocytic lymphoma, DRC with several nuclei were also detectable in situ. These results show that (1) the phenotype of DRC differs from that of all other cell types in lymphoid tissue, (2) this phenotype most nearly resembles that of cells of the monocyte/macrophage series, thus suggesting that DRC are related to these cell lineages, and (3) DRC are multinucleated giant cells.

Antigens↗
PubMed1986

Selective complement fixation by pancreatic B-cells after binding to islet cell surface antibodies.

A two wavelength immunofluorescence system was used to demonstrate islet cell surface antibodies (ICSA) from juvenile diabetics and complement on the same viable rat islet cell. When incubated with rat islet cells at 4 C and at 37 C, ICSA specific for B-cells proved capable of binding complement. In contrast, ICSA specific for both B and non-B cells were able to fix complement on all cell types at 4 C but only on B-cells at 37 C. This study provides further evidence for the B-cell specific cytotoxic effect of ICSA in the presence of complement at physiological temperature. In addition, the ultrastructural events leading to B-cell destruction after ICSA and complement binding were studied by transmission electron microscopy (TEM).

Animals↗
PubMed2006

Insulin inhibits phagocytosis in normal human neutrophils via PKCalpha/beta-dependent priming of F-actin assembly.

OBJECTIVE: This study investigated the effects of insulin on the phagocytosis of C3bi - and IgG-opsonized yeast particles in normal human neutrophils. METHODS: Neutrophils were incubated in different insulin concentrations for 30 minutes and stimulated by C3bi - or IgG-opsonized yeast particles. Phagocytosis was quantified by both light microscopy and FACscan flow cytometry. Laser confocal microscopy was used for quantification of F-actin levels. RESULTS: Elevated insulin concentrations decreased neutrophil phagocytosis of both types of targets. This defect was shown to be in part due to a delayed phagocytosis in the presence of insulin. Following a 30 minute incubation, insulin was found to increase the accumulation of cortical F-actin, without affecting the total cellular F-actin content. The specific PKCalpha/beta inhibitor, Go6976, abolished the insulin-mediated increase in cortical F-actin content and both Go6976 and the PKCalpha/beta/delta/epsilon-specific inhibitor GF109203X reversed the inhibitory effects of insulin on phagocytosis. CONCLUSION: Hyperinsulinemia in vitro can inhibit phagocytosis of opsonized targets in normal human neutrophils. This effect of insulin is dependent on activation of PKCalpha and/or PKCbeta, and these insulin signals may interfere with the dynamic assembly/disassembly and/or distribution of F-actin, which is required for the phagocytosis process.

Actins↗