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Biomedical subjects

M Yazdanbakhsh

Publications and source records attributed to M Yazdanbakhsh.

At least 73 records · Page 4Linked to original sources
PubMed1993

Elevated levels of T cell activation antigen CD27 and increased interleukin-4 production in human lymphatic filariasis.

To assess the immunological changes occurring during filarial infection with or without elephantiasis, 145 patients in different clinical groups from an endemic area in Indonesia were compared with respect to plasma levels of both soluble CD25 (sCD25) and sCD27; interleukin-4 (IL-4) and interferon-gamma release by peripheral blood mononuclear cells was also measured in a smaller subset of individuals. Levels of sCD27 were significantly elevated in elephantiasis and microfilaremic patients compared with endemic normals (p < 0.002), whereas sCD25 levels remained low in microfilaremics and was only slightly elevated in elephantiasis patients compared with endemic normals (p < 0.02). As activated T cell populations release both sCD27 and sCD25, these findings imply that there is filarial-driven activation of a T cell subset that releases sCD27 rather than sCD25. The expansion of a particular T cell population by filarial parasites is further suggested by the enhancement in both IL-4-producing and CD4+CD27-T cells in PBMC from elephantiasis and microfilaremic patients compared with endemic normals. More detailed characterization and comparison of CD27-lymphocytes from these individuals may identify mechanisms involved in the pathogenesis of lymphatic filariasis.

CD4-Positive T-Lymphocytes↗
PubMed1993

T cell responsiveness correlates differentially with antibody isotype levels in clinical and asymptomatic filariasis.

To establish the relationships among T and B cell responses, active infection, and clinical manifestations in lymphatic filariasis, filarial-specific lymphocyte proliferation, IgG antibody isotypes, and IgE levels were determined in an exposed population: 31 asymptomatic amicrofilaremics, 43 microfilaremics, 12 symptomatic amicrofilaremics, and 52 elephantiasis patients. Lymphocyte proliferation was higher in elephantiasis patients and asymptomatic amicrofilaremics than in microfilaremics (P < .004). A proportion of asymptomatic amicrofilaremics (32%), elephantiasis patients (37%), and symptomatic amicrofilaremics (58%) showed antigen-specific lymphocyte unresponsiveness, and lymphocyte proliferation to filarial antigens correlated negatively with specific IgG4 levels (rho = -0.315, P < .001). As elevated specific IgG4 is an indicator of active infection, it is argued that active infection may result in lymphocyte hyporesponsiveness irrespective of clinical category. Of those with elevated specific IgE levels and high T cell proliferative responses, 70% had elephantiasis, suggesting these factors have a role in pathology. However, the existence of a proportion of elephantiasis patients with low anti-filarial IgE and T cell unresponsiveness to filarial antigens suggests that elephantiasis can be caused by distinct processes.

Adolescent↗
PubMed1993

Primary structure of and immunoglobulin E response to the repeat subunit of gp15/400 from human lymphatic filarial parasites.

We have isolated and sequenced clones encoding the repeated subunit of the surface-associated glycoprotein gp15/400 from the two nematode species predominantly responsible for lymphatic filariasis in humans: Brugia malayi and Wuchereria bancrofti. The amino acid sequence of the 15-kDa subunit, derived from the nucleotide sequence of the gene fragment from B. malayi, is identical to that previously reported for B. pahangi, whereas the derived W. bancrofti protein sequence differs in only 7 of 132 residues. The identity of the protein in the two Brugia species allowed us to use a recombinant from B. pahangi to examine the serological response of adult Indonesian subjects infected with B. malayi. The polymerase chain reaction-amplified subunit was expressed in Escherichia coli via the pDS56/RBS11 plasmid and purified by nickel-chelating chromatography. A significant proportion of individuals produced antigen-specific immunoglobulin E (IgE). This was most pronounced in the individuals with elephantiasis, with 14 of 15 showing elevated titers and a mean of 3.2 ng of specific IgE ml-1. Only 2 of 15 microfilaremic individuals possessed elevated titers of specific IgE, with a mean of 0.045 ng ml-1 for the group as a whole. Asymptomatic amicrofilaremic residents showed approximately equal numbers of responders (defined as having a value in the radioimmunoassay greater than two standard deviations above controls) and nonresponders, with a group mean of 1.2 ng of antigen-specific IgE ml-1.

Adult↗
PubMed1991

A proline-rich structural protein of the surface sheath of larval Brugia filarial nematode parasites.

Both cDNA and genomic DNA sequences have been isolated which encode a proline-rich precursor protein of the sheath from microfilariae, the first stage larvae of the filarial nematode parasites Brugia pahangi and Brugia malayi. This 22-kDa protein is soluble only under reducing conditions and is extensively cross-linked by both disulfide and nonreducible bonds. Immunogold electron microscopy shows that the protein is localized exclusively in the sheath, a vestigial remnant of the eggshell, which is retained by and encloses the mature microfilaria. Analysis by Western blotting confirms that the protein is expressed only in microfilariae and adult female worms, although transcripts are detectable only in adult females. The deduced amino acid sequence contains a short N-terminal hydrophobic putative leader sequence, a central repetitive domain that contains 14 copies of a degenerate 5-amino acid repeat with the consensus sequence Met-Pro-Pro-Gln-Gly, and a C-terminal proline-rich domain flanked by clusters of cysteine residues. These clusters can be aligned with cysteine residues implicated in cross-linking of a family of cuticular collagens originally identified in Caenorhabditis elegans but which extends to other nematodes.

Amino Acid Sequence↗
PubMed1991

Immune responses to filarial parasites.

Filarial nematode parasites are long-lived organisms which are responsible for one of the major tropical diseases. Their ability to survive may be related to the antigen-specific anergic state observed in carriers of the parasite. Severe disease symptoms are associated with the breakdown of anergy. Different stages of the parasite life cycle are anti-genetically distinct, and a state of concomitant immunity is therefore possible which prevents superinfection. The evidence for these conclusions is discussed, in the context of the need for an effective vaccine against filarial parasites which will avoid any risk of increasing disease severity.

Animals↗
PubMed1990

Cuticular localisation and turnover of the major surface glycoprotein (gp29) of adult Brugia malayi.

A polyclonal antiserum was raised to a gel purified preparation of the major water-soluble surface glycoprotein (gp29) of adult Brugia malayi, and used to define the stage specificity of expression, localisation (by immunoelectron microscopy) and the dynamics of biosynthesis and turnover via pulse-chase experiments. Gp29 was not detected in surface-labelled preparations of either pre- or post-parasitic third stage larvae (L3), but was present in fourth stage larvae (L4), where its mass was estimated to be 30 kDa by SDS-PAGE. In both L4 and adult worms, the protein resolved as 3 distinct species in 2-dimensional electrophoresis, with pIs from 6.5 to 7.5. Pulse-chase studies via metabolic labelling of adult worms with [35S]methionine in vitro indicated that gp29 was processed from a 32-kDa precursor to the mature molecule within 45 min and that it was secreted into culture medium within 5 h of synthesis. On extended culture, gp29 was converted to a 56-kDa product, presumably either by complex formation or covalent linkage with another secreted molecule. This higher molecular weight component had a more acidic pI of 4.5 and was insensitive to digestion with N-glycanase. Immunoelectron microscopy showed that gp29 was distributed throughout the cuticle and hypodermal cell layer of adult worms, suggesting that the protein was synthesised in the hypodermis, and that turnover into culture medium occurred through the cuticle. The protein appeared to concentrate at the distal cell membrane of the hypodermis, particularly at the stacked invaginations. Additional immunostaining was found on the basement membrane of the basal lamina of the intestine.

Animals↗
PubMed1989

Dual mechanisms in priming of the chemoattractant-induced respiratory burst in human granulocytes. A Ca2+-dependent and a Ca2+-independent route.

After interaction with so-called priming agents, the respiratory burst in human granulocytes does not become activated, but is enhanced upon subsequent stimulation with the chemoattractant FMLP. Investigating the mechanism of the priming reaction, we found that a transient rise in the cytosolic free calcium concentration [( Ca2+]i) suffices to irreversibly prime human granulocytes. Thus, platelet-activating factor (PAF) induced a transient increase in [Ca2+]i and primed the cells to an enhanced respiratory burst upon subsequent interaction with FMLP. Artificially, the transient rise in [Ca2+]i was mimicked by addition and subsequent removal of the Ca2+ ionophore ionomycin; this treatment too, primed the respiratory burst of the granulocytes. The priming induced by ionomycin was completely abolished when [Ca2+]i changes were buffered during exposure of the cells to the ionophore. The priming induced by PAF was only partially inhibited under [Ca2+]i-buffering conditions during priming, indicating that multiple pathways exist in the priming of granulocytes by PAF.

Buffers↗
PubMed1987

Synergism between eosinophil cationic protein and oxygen metabolites in killing of schistosomula of Schistosoma mansoni.

To study the cytotoxic reactions responsible for mediating eosinophil damage to schistosomula of Schistosoma mansoni, we have used cytoplasts (eosinophil or neutrophil vesicles devoid of granules and nuclei, with an intact oxidase in their plasma membrane) in combination with purified eosinophil cationic protein (ECP) or major basic protein (MBP) in a cytotoxicity test toward schistosomula. Suboptimal concentrations of ECP (10(-6) M) or MBP (10(-6) M) resulting in less than 10% killing were used in combination with cytoplasts. Cytoplasts alone in the presence of immune serum tested over a wide range of cytoplast:schistosomula ratios generated superoxide and hydrogen peroxide, but were unable to damage schistosomula. However, when a suboptimal ECP concentration (10(-6) M) was combined with neutroplasts or eosinoplasts, 43.9% +/- 8.5 (n = 7) and 24.7% +/- 9.8 (n = 3), respectively, of the schistosomula were killed. Oxygen metabolites were responsible for the synergism, because cytoplasts from a patient with chronic granulomatous disease were unable to act in synergy with ECP. In contrast to ECP, no synergism was found between cytoplasts and MBP (10(-6) to 2 X 10(-5)M). These results show that oxygen metabolites are important for the killing of schistosomula by lowering the concentration of ECP needed to inflict damage.

Animals↗
PubMed1987

Killing of schistosomula by taurine chloramine and taurine bromamine.

Eosinophils generate hypochlorous acid when stimulated with opsonized particles. The hypochlorous acid can react with beta-amino acids such as taurine to produce chloramines with a long lifetime. In the presence of bromide, eosinophils generate hypobromous acid which can react with taurine to generate taurine bromamine. As taurine is abundantly present in leukocytes, eosinophils have the potential to generate taurine chloramine or taurine bromamine. With regard to the role of eosinophils in killing schistosomula, we have shown that both taurine chloramine and taurine bromamine in physiological concentrations are able to kill the schistosomula of Schistosoma mansoni.

Animals↗
PubMed1987

Eosinophils do respond to fMLP.

Eosinophils were isolated from normal human blood by separation over Percoll gradients, which resulted in eosinophil suspensions of a purity higher than 95% and recoveries of about 65%. Normal human eosinophils were found to respond to formyl-methionyl-leucyl-phenylalanine (fMLP) at concentrations greater than 10(-7) mol/L with an increase in the concentration of intracellular free calcium, oxygen consumption, nitroblue tetrazolium reduction, and chemiluminescence. The maximal response of eosinophils to fMLP was lower than that of neutrophils isolated from the same blood samples and required at least ten times as much fMLP as was needed for neutrophils. Low fMLP concentrations (approximately 10(-8) mol/L), which in themselves did not stimulate O2 consumption by either eosinophils or neutrophils, primed these cells to respond to a suboptimal concentration of another stimulus. Purification of eosinophils after treatment of whole blood with fMLP showed that these eosinophils had lost their ability to respond to fMLP. We conclude that normal eosinophils do respond to fMLP and that therefore fMLP should not be used to isolate eosinophils.

Acridines↗
PubMed1987

Purification of eosinophils from normal human blood, preparation of eosinoplasts and characterization of their functional response to various stimuli.

Eosinophils from the blood of normal individuals were purified by centrifugation over discontinuous Percoll gradients. Eosinophil suspensions were obtained with a mean purity of 96% and a mean recovery of 64% (n = 19). When incubated with phorbol-myristate acetate, eosinophils consumed twice as much oxygen as did neutrophils from the same donors. With serum-treated zymosan, 70% and 100% of the maximal oxidative response (i.e. the response to phorbol-myristate acetate) was obtained with eosinophils and neutrophils, respectively. The calcium ionophore A23187 is a weak stimulus that triggered only 2.5% of the eosinophil and 10% of the neutrophil oxidative capacity. The response of both cell types to formyl-methionyl-leucyl-phenylalanine (fMLP) was rapid, with a maximum after 3 min. The magnitude of this eosinophil reaction was half that of neutrophils. Although the activities of the granule enzymes beta-glucuronidase and arylsulphatase were 2.5 and 6 times higher in eosinophils than in neutrophils, respectively, the exocytosis of these enzymes in response to various stimuli was lower in eosinophils. The high yield of eosinophils from our separation method enabled us to prepare eosinoplasts by centrifugation of eosinophils over discontinuous Ficoll gradients that contained cytochalasin B. Eosinoplasts are plasma membrane vesicles derived from eosinophils, filled with cytoplasm but devoid of granules and nucleus. The eosinoplasts contained 30% of the cytoplasm and plasma membrane present in intact eosinophils. Eosinoplasts still possessed a functionally intact oxidase enzyme that could be stimulated with various stimuli. Therefore, eosinoplasts may provide a valuable tool to study separately the role of the oxidase products and that of the granule contents in eosinophil functions.

Arylsulfatases↗
PubMed1986

Bactericidal action of eosinophils from normal human blood.

The ability of normal human eosinophils to ingest and kill Staphylococcus aureus and Escherichia coli was investigated and compared with the reactions shown by neutrophils from the same donors. The rate of phagocytosis of S. aureus by eosinophils was 50% of that shown by neutrophils. Unlike neutrophils, eosinophils were not able to kill ingested S. aureus at low bacterium/phagocyte ratios. The degree of S. aureus killing increased with increasing ratios, being equal to that of neutrophils when bacterium/phagocyte ratios of about 15 were used. This was probably due to a better triggering of the eosinophil oxidase system at high bacterium/phagocyte ratios. The early kinetics of the association of bacteria with eosinophils, the perforation of the bacterial envelope and the inactivation of bacterial proteins, was monitored in the ML-35 mutant strain of E. coli. The association of E. coli with eosinophils was 70% of that with neutrophils. Eosinophils had only 25% of the capacity of neutrophils to perforate the E. coli envelope. E. coli loses its colony-forming ability when the bacterial envelope has been perforated, indicating that eosinophils also kill E. coli more slowly than do neutrophils. This was confirmed with a plating assay for colony formation. The perforation of E. coli is independent of peroxidase-mediated reactions. Hence, the defective bactericidal action of eosinophils is probably not related to the differences between myeloperoxidase and eosinophil peroxidase. On the other hand, the inactivation of bacterial proteins is peroxidase dependent and was also seen to occur to a lesser extent in eosinophils compared with neutrophils. We conclude that eosinophils ingest E. coli but only slowly perforate (kill) these bacteria and barely inactivate the bacterial enzymes. In contrast, neutrophils quickly ingest and perforate (kill) E. coli and quickly inactivate the bacterial enzymes.

Blood Bactericidal Activity↗
PubMed1985

Characterization of the interaction of human eosinophils and neutrophils with opsonized particles.

The interaction of human eosinophils with opsonized particles was compared with that of human neutrophils. When eosinophils are stimulated with serum-opsonized zymosan particles, the lag time in H2O2 production is twice as long as found with neutrophils. Moreover, the concentration of these IgG + C3-coated particles required for optimal stimulation is about four times as high for eosinophils as for neutrophils. Under these conditions, the two cell types generate similar amounts of H2O2. However, eosinophils produce twice as much H2O2 as do neutrophils when stimulated with the soluble agent phorbol myristate acetate. Thus, although the oxidase capacity of eosinophils is larger than that of neutrophils, opsonized zymosan is a weak trigger for this activity in eosinophils. This phenomenon may be due to differences between the two cell types in the plasma membrane receptors or in the receptor oxidase transducing signal. The following are indications for the first possibility. i) IgG interacts poorly with the Fc gamma receptors on the eosinophil surface compared with those on neutrophils. This was shown by the inability of IgG-coated zymosan or IgG-coated latex to trigger any substantial H2O2 production by eosinophils unless brought into close contact with these cells by centrifugation. In contrast, neutrophils are stimulated by these particles both in suspension and in a pellet. The dissimilarity of the Fc gamma receptors on eosinophils and neutrophils was also shown with respect to antigenicity, determined by the monoclonal antibodies 3G8 and CLB-FcR-1. ii) Eosinophils contain about half as many receptors for C3b and C3bi on their surface as do neutrophils, also detected with monoclonal antibodies. The interaction of IgG subclasses with functional Fc gamma receptors on eosinophils and neutrophils showed that eosinophils release twice as much H2O2 as do neutrophils upon interaction with IgG1-, IgG2-, or IgG3-coated Sepharose beads, but this difference becomes fivefold with IgG4-coated Sepharose. This might be of relevance to the situation of chronic antigenic stimulation, e.g., in chronic schistosomiasis, in which eosinophil numbers and IgG4 antibody levels are elevated.

Antibodies, Monoclonal↗
PubMed1984

Excretion of superoxide by phagocytes measured with cytochrome c entrapped in resealed erythrocyte ghosts.

Resealed erythrocyte membranes (ghosts) filled with (Fe3+)cytochrome c were used as an assay system to measure the release of superoxide (O-2) from human phagocytes into the incubation medium. Neutrophils, activated by either opsonized zymosan particles or the soluble stimulus phorbol myristate acetate, released O-2, which subsequently entered the ghosts and reduced (Fe3+)cytochrome c. This reaction was dependent on the time of incubation, the concentration of neutrophils, the concentration of stimulus, and the concentration of ghosts. The reaction was completely inhibited by superoxide dismutase and by 4,4'-diisothiocyano-2,2'-disulfonic acid, a specific blocker of anion channels in membranes. The reduction of (Fe3+)cytochrome c free in solution was about four times as fast as the reduction of (Fe3+)cytochrome c in the ghosts. Human eosinophils stimulated by phorbol myristate acetate reacted similarly to human neutrophils; the rate of O-2 production/cell was about twice as high for eosinophils as for neutrophils. In contrast, eosinophils stimulated with opsonized zymosan particles only reduced (Fe3+)cytochrome c free in solution, but not (Fe3+)cytochrome c in ghosts. This lack of reaction was not due to production of an inhibitor or below threshold generation of O-2 for the ghost assay. These results indicate: 1) activated human neutrophils and eosinophils can release O-2 or a similar product into the incubation medium; and 2) reduction of (Fe3+)cytochrome c free in solution is no proof for O-2 excretion by phagocytes.

Animals↗
PubMed1982

Effects of ethanol administration on platelet function in the rat.

When ethanol is administered to rats chronically by inhalation for 5-7 days to produce a final ethanol concentration in plasma of about 50 mM platelet aggregation in vitro to collagen is markedly inhibited. Platelet aggregation to ADP is relatively unaffected and there is no evidence of thrombocytopenia or morphological change in platelets on scanning and transmission electron microscopy. The changed sensitivity to collagen is not simply due to the presence of ethanol in plasma during the in vitro tests because in vitro addition of a similar concentration of ethanol produces a much smaller inhibition of platelet aggregation to collagen in platelet-rich plasma from control animals. The acute or subacute administration of ethanol either by injection (3 g/kg-1 intraperitoneally) or by inhalation (4-6 h) produced very variable results, platelets from some animals being inhibited with respect to collagen as much as those from animals chronically exposed to ethanol, whereas other showed no inhibition other than that attributable to the presence of ethanol in plasma. When ethanol was administered chronically by inhalation for 30 days, thrombocytopenia was apparent and platelets from these animals were unresponsive to all aggregating agents tested. It is concluded that even relatively short periods of ethanol intake may lead to significant inhibition of platelet function, specifically aggregation to collagen. This may be of relevance to the suggested protective effect of ethanol intake in cardiovascular disease.

Adenosine Diphosphate↗