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I Esparza

Publications and source records attributed to I Esparza.

At least 19 recordsLinked to original sources
PubMed1992

Segment spanning residues 727-768 of the complement C3 sequence contains a neoantigenic site and accommodates the binding of CR1, factor H, and factor B.

CR1, CR2, DAF, MCP, factor H, C4bp, factor B, and C3 are members of a family of structurally related molecules, the majority of which belong to the complement system. Several of these molecules also share functional features such as cofactor and decay/dissociation activity and compete with one another in binding to C3b. Since factor H appears to bind to multiple sites in C3, we investigated the relationship between the factor H- and CR1-binding sites in C3b. Factor H binding to C3b is inhibited by either the C3c or C3d fragments, and addition of both fragments together augments this inhibition. One monoclonal anti-C3c antibody, anti-C3-9, which recognizes a neoantigenic epitope expressed upon cleavage to C3 to C3b, inhibited both factor H and CR1 binding to EC3b cells. This monoclonal antibody (MoAb) also inhibited factor B binding to EC3b. Two observations further supported our hypothesis that these molecules bind to proximal sites in C3b. First, a synthetic peptide spanning this region of C3b (C3(727-768)) inhibited factor H binding. Second, antibodies raised against this peptide inhibited binding to CR1, factor H, and factor B to C3b. These data show that H binds to at least two sites in C3b: the site in the C3c fragment is within the identified CR1-binding domain while the site in the C3d fragment surrounds the CR2-binding site.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1992

Parameters affecting the immunogenicity of microencapsulated tetanus toxoid.

The immunogenic potential of tetanus toxoid (TT) was compared when either adsorbed to aluminium hydroxide (TT-alum) or entrapped in microparticles consisting of poly(D,L-lactic-co-glycolic acid) (PLA:PGA, 55:45) derived polymers. Furthermore, the effect of administering the microparticles in an aqueous buffer or water-in-oil emulsion on the TT immunogenicity was also investigated. When mice were immunized with the different formulations, similar levels of anti-TT antibodies were observed during the primary IgG response. The choice of the carrier seemed to play an important role for both the level and maintenance of the secondary IgG response, attained as a consequence of a booster immunization with TT-alum. The strongest secondary antibody response was obtained by priming with TT-containing microparticles, resuspended in water-in-oil emulsions. As expected, incomplete Freund's adjuvant (IFA) proved to be a more potent adjuvant than peanut oil, whereas resuspension of the microparticles in aqueous solution induced a relatively less efficient antibody response. Overall, microencapsulated TT primed the mice more effectively, since the secondary antibody response was higher and persisted longer compared with TT-alum priming. These results indicate that in addition to TT maintaining its antigenicity after microencapsulation, the microparticles also potentiate its immunogenic properties. This approach should prove very useful for designing more effective vaccines.

Adjuvants, Immunologic↗
PubMed1991

Evidence for multiple sites of interaction in C3 for complement receptor type 2 (C3d/EBV receptor, CD21).

Multivalent but not monovalent CR2 ligands are required to elicit Raji cell proliferation as well as other B cell responses. It has been reported (C. Servis and J. D. Lambris, J. Immunol. 1989. 142: 2207) that the tetrameric peptide T-(C31202-1214)4, which represents the CR2-binding site in C3d, was able to support Raji cell growth. We show here that the tetrameric peptide T-(gp350(19-30)4, which contains the CR2-binding site in gp350 protein of EBV also induces Raji cell growth and this effect is inhibited by the monomeric peptides gp350(19-30) and C3(1201-1214). We also investigated the nature of the interaction between C3 fragment and CR2 in order to explain the Raji cell growth-supporting effect exerted by C3. The following findings suggest that there are multiple sites in the C3 molecule able to interact with CR2: (1) both C3c and C3d immobilized on microspheres are able to bind to Raji cells through CR2. (2) soluble C3d inhibits to a greater extent the binding of CR2 to fixed C3d than to fixed C3b, which suggests the existence of additional CR2-binding sites within C3b not present in the C3d portion of the molecule; (3) synthetic peptides C3(1187-1214), C3(741-757) and C3(295-307) which represents regions of similarity in the C3 molecule bind specifically to CR2 on Raji cells and compete with each other for binding to the receptor and (4) preincubation of microtiter plate-fixed C3b with monoclonal or polyclonal anti-peptide antibodies (C3-9, anti-C3(727-768) recognize the N terminus of the alpha chain of C3 (including residues 741-757) inhibited CR2 binding. Therefore, these data suggest that the N terminus of the alpha chain of C3 is involved in binding to CR2.

Amino Acid Sequence↗
PubMed1988

Preactivation of macrophages in mice acutely infected with Schistosoma mansoni.

This paper shows that peritoneal murine macrophages become preactivated in vivo during the course of a Schistosoma mansoni infection. Thus, less macrophage-activating factor (MAF) was required to induce in vitro tumoricidal and schistosomulicidal activity in macrophages from S. mansoni-infected mice than in macrophages from uninfected control animals. Moreover, the respiratory burst activity, as measured by chemiluminescence, was enhanced in macrophages from S. mansoni-infected mice as compared to controls, whether or not lymphokine (LK) was present in the macrophage cultures. This response appeared at 3 weeks and persisted at least until 12 weeks after infection. Interferon-gamma (IFN-gamma) is most likely involved in the mechanisms leading to such an increased cytolytic and oxidative activity, since in vitro experiments showed: 1) that less IFN-gamma was required to induce tumoricidal activity in macrophages from infected as compared to macrophages from uninfected animals, 2) that the activity of (2'-5')-adenylate synthetase (2'-5' A-synthetase), an enzyme strongly induced by IFN, was elevated in cells from livers of S. mansoni-infected mice.

Animals↗
PubMed1988

Effect of interferon-alpha, interferon-gamma and tumour necrosis factor on African swine fever virus replication in porcine monocytes and macrophages.

Bovine interferon-alpha I1 (IFN-alpha I1) and porcine interferon-gamma (IFN-gamma) inhibited African swine fever virus replication in both porcine monocytes and alveolar macrophages. The most potent antiviral activity was observed with IFN-gamma-treated alveolar macrophages. The production of both a virulent (CC83) and a non-virulent (BA71) isolate of the virus was inhibited. Bovine tumour necrosis factor alpha did not show antiviral activity in either monocytes or alveolar macrophages. Rather, an increase of African swine fever virus production in tumour necrosis factor alpha-treated monocytes was found. An analysis of viral protein synthesis in IFN-alpha I1- and IFN-gamma-treated alveolar macrophages showed an inhibition of synthesis of some viral proteins. The inhibition of late proteins was very pronounced in IFN-gamma-treated cells, and it was probably a consequence of the inhibition of African swine fever virus DNA polymerase activity.

African Swine Fever Virus↗
PubMed1987

Interferon gamma and lymphotoxin or tumor necrosis factor act synergistically to induce macrophage killing of tumor cells and schistosomula of Schistosoma mansoni.

Macrophages play a crucial role in the defense against tumors and parasites. Activation of tumoricidal and microbicidal effector mechanisms requires stimulation of macrophages with macrophage-activating factors (MAF). One such MAF is interferon gamma (IFN-gamma). In some assays, substantial activity of IFN-gamma on murine macrophages, however, is only observed in synergy with lipopolysaccharide (LPS) or other cytokines (1). In addition, certain cytokines have been shown to induce monocyte or macrophage activation in the absence of IFN-gamma (2-5). We previously described lymphokines in the supernatant of a murine T cell clone that synergized with IFN-gamma in the induction of tumoricidal and schistosomulicidal murine macrophages (1). We called this lymphokine(s) macrophage cytotoxicityinducing factor 2 (MCIF2)(1). A candidate for MCIF2 was lymphotoxin (LT), because the T cell clone supernatant contained high amounts of LT. LT is functionally homologous and structurally related to the macrophage product tumor necrosis factor (TNF). Therefore, we tested whether recombinant (r) LT or rTNF can function as MAF. We report here that rLT or rTNF synergize with rIFN-gamma in the induction of tumoricidal and schistosomulicidal murine macrophages.

Cells, Cultured↗
PubMed1986

Interferon-gamma-dependent modulation of C3b receptors (CR1) on human peripheral blood monocytes.

Cell surface expression of the C3b receptor (CR1) was transiently down regulated on purified human monocytes exposed to purified recombinant human interferon-gamma(rIFN-gamma). Receptors were quantitated by using CR1-specific monoclonal antibody by radioimmunoassay or flow cytometry and by rosette analysis with the use of C3b-coated bovine erythrocytes. The reduction of CR1 was dependent on the dose of IFN-gamma used and the time of cellular exposure. Down-regulation was transient, with maximum loss occurring after 2 to 3 days of stimulation with IFN-gamma. However, after 6 days CR1 was re-expressed at the plasma membrane. This effect was observed with monocytes isolated by either centrifugal elutriation or adherence on fibronectin-coated dishes. IFN-gamma-dependent diminution of CR1 occurred concomitant with increased expression of Fc receptors and HLA-DQ antigen and unaltered expression of the C3bi receptor (CR3). The mechanism of CR1 loss from the monocyte cell surface was not due to internalization, because total cellular levels of CR1 (plasma membrane and intracellular pool) also decreased in response to IFN-gamma. These results indicate that IFN-gamma may be involved in regulating CR1 on mononuclear phagocyte surfaces.

Cell Line↗
PubMed1985

Demonstration and partial characterization of the interferon-gamma receptor on human mononuclear phagocytes.

Radioiodinated recombinant human interferon-gamma (IFN gamma) bound to human monocytes, U937, and HL60 cells in a specific, saturable, and reversible manner. At 4 degrees C, the different cell types bound 3,000-7,000 molecules of IFN gamma, and binding was of comparable affinity (Ka = 4-12 X 10(8) M-1). No change in the receptor was observed after monocytes differentiated to macrophages or when the cell lines were pharmacologically induced to differentiate. The functional relevance of the receptor was validated by the demonstration that receptor occupancy correlated with induction of Fc receptors on U937. Binding studies using U937 permeabilized with digitonin showed that only 46% of the total receptor pool was expressed at the cell surface. The receptor appears to be a protein, since treatment of U937 with trypsin or pronase reduced 125I-IFN gamma binding by 87 and 95%, respectively. At 37 degrees C, ligand was internalized, since 32% of the cell-associated IFN gamma became resistant to trypsin stripping. Monocytes degraded 125I-IFN gamma into trichloroacetic acid-soluble counts at 37 degrees C but not at 4 degrees C, at an approximate rate of 5,000 molecules/cell per h. The receptor was partially characterized by SDS-polyacrylamide gel electrophoresis analysis of purified U937 membranes that had been incubated with 125I-IFN gamma. After cross-linking, the receptor-ligand complex migrated as a broad band that displayed an Mr of 104,000 +/- 18,000 at the top and 84,000 +/- 6,000 at the bottom. These results thereby define and partially characterize the IFN gamma receptor of human mononuclear phagocytes.

Cell Differentiation↗
PubMed1984

The nature of iron released by resident and stimulated mouse peritoneal macrophages.

Mouse peritoneal macrophages were allowed to ingest 59Fe, 125I-labelled transferrin-antitransferrin immune complexes, and the release of 59Fe and degraded transferrin was studied. Some iron was released as ferritin, but a major portion was bound by bovine transferrin present in the culture medium, which contained fetal calf serum. If the medium was saturated with iron prior to incubation with the cells, little of the released iron was then bound by transferrin but appeared either as a high molecular weight fraction or, if nitrilotriacetate was present in the medium, some also appeared as a low molecular weight fraction. The release of non-ferritin iron was biphasic, the early, rapid phase being more prolonged with resident cells than with stimulated cells. The rate of release in the late phase did not differ significantly between resident and stimulated cells. Incubation at 0 degrees C completely suppressed the release of degraded transferrin, but iron release continued at about 30% of the rate seen in control cultures at 37 degrees C. A model for the intracellular handling of ingested iron is proposed to take account of the different release patterns of resident and stimulated macrophages.

Animals↗
PubMed1983

Inhibition of macrophage tumoricidal activity by immune complexes and altered erythrocytes.

Engagement of the macrophage membrane by biologic particles including insoluble immune complexes inhibited the development of lymphokine-mediated nonspecific tumoricidal activity by murine macrophages. The degree of inhibition was dependent on the dose of particles and the lymphokine concentration. Inhibition was not due to macrophage cell death or to diminution of cell adherence after ingestion of the immune complexes. Soluble immune complexes were not inhibitory, although approximately 10% of the complexes became cell-associated. Monomeric or heat-aggregated IgG was also not inhibitory. IgG-opsonized erythrocytes (EA) were inhibitory and inhibition was dependent on the degree of opsonization. In contrast, nonopsonized erythrocytes (E), which did not bind to macrophages, were not inhibitory. Phagocytosis of glutaraldehyde-treated E or E carrying IgM antibody and complement (EAC) also led to a reduction of tumorilytic activity. Insoluble immune complexes were inhibitory when added either before or after lymphokine. Phagocytosis was neither sufficient nor necessary to cause inhibition because 1) ingestion of polystyrene latex beads did not diminish tumoricidal activity, and 2) macrophages plated on IgG-coated surfaces were inhibited with respect to the tumoricidal function. Inhibition was not affected when indomethacin (10(-6) M) was included in the assay, which indicated that prostaglandins were not involved in the process. Thus, macrophage tumoricidal responsiveness may be compromised by interaction of biologic substances with macrophage plasma membranes. This process may thereby inactivate an important host defense mechanism against neoplastic cells.

Animals↗
PubMed1981

Release of iron by resident and stimulated mouse peritoneal macrophages following ingestion and degradation of transferrin-antitransferrin immune complexes.

A method of loading macrophages from normal and inflammatory mouse peritoneal exudates with 59Fe using 59Fe, 125I-transferrin-antitransferrin immune complexes is described and the subsequent release of iron and degraded transferrin to the incubation medium has been studied. Release of iron occurred more rapidly from resident macrophages than from thioglycollate broth-induced (stimulated) macrophages, but degradation of the 125I-transferrin in the immune complexes was faster in stimulated cells. A small percentage of the iron released was in the form of ferritin. Desferrioxamine (1 mM) increased the release of iron from both stimulated and resident macrophages, the effect being proportionally greater in the stimulated cells. Ascorbic acid (1 mM) had no effect on the release of iron, nor did the addition of apotransferrin (1 mg/ml) to the culture medium. These results support the concept of a blockade of iron release by reticuloendothelial cells in states of inflammation, and suggest that it may be a primary cause of the anaemia of chronic disease.

Animals↗
PubMed1980

The interaction of bovine transferrin and monoferric transferrin fragments with rabbit reticulocytes.

1. The mechanism of interaction of transferrin with reticulocytes has been investigated using monoferric fragments derived by proteolysis from bovine Fe2-transferrin. 2. Rabbit reticulocytes readily took up iron from bovine transferrin, but only slight uptake occurred from the C-terminal fragment (S), and almost none from the N-terminal fragment (F). 3. The degree of binding of transferrin and fragments to the cells was in the order transferrin greater than fragment F greater than fragment S. 4. Binding of transferrin and fragment S, but not of fragment F, was reduced when incubation was performed at 4 degrees C instead of 37 degrees C, and all iron uptake was abolisehd. 5. Preincubation of reticulocytes with fragment S, but not with fragment F, somewhat reduced subsequent iron uptake from transferrin. 6. The presence of bovine serum albumin (40 mg/ml) in the incubation buffer inhibited iron uptake, but iron uptake nevertheless occurred from transferrin in bovine serum. 7. No differences were detected in the rate of 59Fe uptake from transferrin labelled asymmetrically by sequential additions of 59Fe and 56Fe to apotransferrin. 8. It is concluded that both halves of the transferrin molecule are involved, perhaps in different ways, in the interaction of transferrin with reticulocytes, and that rabbit reticulocytes do not take up iron preferentially from one of the binding sites of bovine transferrin.

Animals↗
PubMed1980

The effect of trypsin digestion on the structure and iron-donating properties of transferrins from several species.

The effect of trypsin digestion on iron-saturated and iron-free (apo) human, rabbit, bovine, pig and horse tranferrins has been studied. Iron-binding fragments were produced only from iron-saturated pig and bovine transferrins although some cleavage of the polypeptide chain occurred in all cases. The apo-transferrins were generally degraded to a greater extent than the corresponding iron-saturated proteins. The ability of the different transferrins to donate iron to rabbit reticulocytes varied in the order rabbit approximately pig greater than human approximately horse greater than bovine. Trypsin digestion considerably reduced the ability of pig and bovine transferrins to donate iron to rabbit reticulocytes, slightly reduced the iron-donating ability of rabbit transferrin, and had almost no effect on that of human or horse transferrins.

Animals↗
PubMed1980

Electrophoretic mobility of N- and C-terminal monoferric fragments of bovine transferrin phenotypes AA, D1D1, D2D2, and EE, and N-terminal amino acid sequences.

Iron-saturated bovine transferrins A, D1, D2 and E were cleaved by trypsin yielding monoferric fragments. The N-terminal fragments (F) of transferrins A and D2 had identical mobility in cellulose acetate electrophoresis, that of transferrin D1 a slower mobility, and that of E a still slower mobility. The C-terminal fragments (S) gave multiple bands which were essentially identical in the case of transferrins A, D1, and E, but of slower mobility in the case of transferrin D2. All four variants had identical N-terminal amino acid sequences. The electrophoretic mobility of the C-terminal fragments was reduced by neuraminidase treatment, but the N-terminal fragments were unaffected. The four transferrin variants therefore appear to be made up from three electrophoretically distinguishable N-terminal halves and two C-terminal halves. The feature responsible for the electrophoretic double banding of homozygous bovine asialotransferrins is consistently associated with the C-terminal half of the molecule.

Amino Acid Sequence↗