Biomedical subjects

I Mota

Publications and source records attributed to I Mota.

At least 55 records · Page 3Linked to original sources

PubMed1991

The possible mechanism of action of IgG antibodies and platelets protecting against Trypanosoma cruzi infection.

1. The role of IgG antibody and platelets in the mechanism of defense against Trypanosoma cruzi infection is reviewed. 2. Experimental data showing the participation of the different IgG subclasses in the immune lysis and immune clearance of the parasites are discussed. 3. The involvement of the platelets in the removal of the parasites from the circulation is considered. 4. It is suggested that IgG anti-T. cruzi antibodies interact with circulating parasites leading to formation of microaggregates, activation of C3 and deposition of C3b on the immune aggregates followed by adherence of platelets through C3b receptors. The immune aggregates would then be taken up by cells of the mononuclear phagocytic system.

Animals↗

PubMed1991

Isolation of horse IgG with protein A.

Horse immunoglobulins were obtained from normal serum defatted with dextran sulfate and precipitated with ammonium sulfate. Eight mg of this preparation was submitted to affinity chromatography with protein A-Sepharose CL-4B. Low temperature (4 degrees C) and a starting buffer at pH 8.0 were conditions required for all IgG subclasses to bind to protein A, even those with low affinity. The IgGs bound to protein A were eluted with glycine buffer at pH 2.8. The yield was about 90%. It is suggested that isolated IgG, instead of whole Igs, be used in serum therapy, reducing the amount of Igs and diminishing serum-related reactions.

Animals↗

PubMed1991

Suppression of the IgE antibody response by Ascaris suum components: effect of X-irradiation.

The effect of X-irradiation on the suppression of IgE antibody responses induced by some of the Ascaris suum (ASC) components was analyzed in mice (7-week old A/Sn females). Treatment with 300 R 24 h before immunization with 50 micrograms OVA and 200 micrograms ASC suppressive components abolished the damping effect on anti-OVA IgE antibody levels. The same effect was observed on the anti-ASC IgE antibody response obtained in mice injected with 200 micrograms ASC immunogenic plus 200 micrograms ASC suppressive components. Moreover, the failure of suppressive components to induce an IgE anti-ASC antibody response on their own was also abolished by X-irradiation. These results indicate that the suppressive components are able to elicit an IgE antibody response, but simultaneously activate a regulatory mechanism which suppresses both the homologous (anti-ASC) and heterologous (anti-OVA) antibody formation.

Animals↗

PubMed1990

The humoral immune responses of patients bitten by the snake Bothrops jararaca (jararaca).

The isotype and specificity of antibodies produced by patients bitten by B. jararaca and submitted to serum therapy were studied. The IgG anti-B. jararaca antibodies have large individual dispersion, starting to appear 10 days after the first bite and increasing to at least 80 days after the bite. IgM antibodies appeared sooner than IgG antibodies but disappeared about 20 days after the bite. Secondary responses induced by an additional bite were characterized by a fast and higher IgG antibody response with no apparent change in the IgM antibody. The immunoblotting tests showed that the specificity of human anti-B. jararaca antibodies is heterogeneous, each patient recognizing different fractions in the B. jararaca venom.

Crotalid Venoms↗

PubMed1990

Antigenic cross-reactivity of venoms obtained from snakes of genus Bothrops.

Antigenic cross-reactivity was studied among the components of venoms from nine species of the genus Bothrops using species-specific antivenoms. Sera titration by DOT-ELISA detected similar levels of antibody when either homologous or heterologous antigens were used. Transblotted antigens, after SDS-PAGE fractionation, were also revealed by homologous and heterologous antivenoms. Antigens with mol. wt greater than 30,000 seemed to be the most cross-reactive. Antigens of about 24,000 mol. wt were poorly immunogenic. Antigens between 14-18,000 mol. wt cross-reacted only with B. moojeni, B. jararacussu, B. neuwiedi and B. pradoi venoms. Neutralization of the lethality of B. jararaca venom was observed by homologous and heterologous antivenoms.

Animals↗

PubMed1990

Further characterization of Ascaris suum component(s) with suppressive activity on the IgE antibody response.

In order to characterize the component(s) of Ascaris suum responsible for damping of the IgE antibody production we demonstrated that the extract incubated in sodium acetate buffer, pH 4.5, maintained its suppressive effect and the same protein banding pattern by SDS-PAGE. Elimination of the lipoprotein components of the extract also left its damping properties unchanged. SDS-PAGE of the lipoprotein-free extract revealed practically the same pattern as shown by the whole extract, except for the high molecular weight polypeptides. These results indicate that the suppressive component(s) of A. suum did not precipitate and retained their activity at low pH. In addition, they appear not to be lipoproteins.

Animals↗

PubMed1990

Role of platelets in the in vivo removal of T. cruzi from circulation.

The possible role of platelets in the clearance of Trypanosoma cruzi was studied in vivo in A/sn female mice. Platelet depletion achieved by anti-platelet IgG antibodies induced a significant, though not total, reduction in the rate of removal of T. cruzi bloodstream trypomastigotes (BTRYS) from the circulation. Furthermore, during removal of T. cruzi BTRYS from the circulation of normal mice there was a simultaneous decrease in the number of platelets. These results suggest that platelets play a role in the in vivo mechanism of defense against T. cruzi infection.

Animals↗

PubMed1989

The effect of C3 depletion on the clearance of Trypanosoma cruzi induced by IgG antibodies.

Passive transfer of homologous immune serum or IgG anti-Trypanosoma cruzi antibodies to normal mice containing circulating T. cruzi bloodstream trypomastigotes (Btrys) induces a very fast clearance of the parasites. Previous work from this laboratory has shown that F(ab')2 fragments obtained from IgG anti-T. cruzi antibodies retain the ability to induce lysis of the Btrys but are unable to induce clearance of the parasites. This suggests that the clearance is dependent on the Fc region. The removal of the Btrys may then be effected by attachment of the antibodies to the parasites and removal of the opsonized parasites by the mononuclear phagocytic system. Attachment of the opsonized parasites to macrophages may be effected either through the Fc receptor that binds specifically to the heavy chain of IgG or through C3b fragments after cleavage of C3 by C3-convertases. In order to find out the possible role of C3b in this phenomenon the clearance of Btrys was determined in mice depleted of C3 by previous treatment with cobra venom factor. The results of these experiments showed that depletion of C3 completely abolished the immune clearance induced by anti-T. cruzi antibodies. It is suggested that C3 is required for the clearance of Btrys from circulation.

Animals↗

PubMed1989

A comparative study of anti-Trypanosoma cruzi serum obtained in acute and chronic phase of infection in mice.

The IgG antibody content, specificity, lytic activity, clearance capacity and protective ability of mouse anti-Trypanosoma cruzi serum was determined during the course of infection. The IgG antibody content increased during the course of infection, reaching its highest level in the serum collected in the chronic phase of the infection. The T. cruzi antigens recognized by antibodies using the protein transfer technique also increased with time of infection. Antibodies present in day 22 post-infection (p.i.) serum were already able to recognize all the antigens detected by antibodies present in serum from the chronic phase. The lytic and clearance ability were not detected on day 7 p.i., but appeared on day 14 p.i. and reached their highest level on day 45 p.i. The protective ability was present in serum of the chronic phase, but was absent from the acute serum. The IgG antibody content of the acute serum was four times less than that of the chronic serum. When the IgG antibody concentration of the acute serum was equalized to that of the chronic serum, the acute serum was as able to protect the infected animals as the chronic serum. It is suggested that the disagreement between the protective ability of anti-T. cruzi antisera collected in the acute or in the chronic phase of the infection is due to a quantitative rather than a qualitative difference.

Acute Disease↗

PubMed1989

IgG subclasses responsible for immune clearance in mice infected with Trypanosoma cruzi.

To examine the role of different immunoglobulin subclasses in the immune clearance of Trypanosoma cruzi, mice containing bloodstream trypomastigotes were injected intravenously with immune serum, IgG-depleted serum, or with the IgG1 or IgG2 fractions and the rate of removal of the parasites from circulation was determined. Using IgG concentrations similar to those found in the immune serum, the rate of clearance mediated by IgG2 was six-fold higher than that obtained with IgG1. This difference did not appear to be due to differences in antibody specificity, as Western blotting showed that each isotype recognized a similar set of antigens extracted from the parasite. However, the T. cruzi specific antibody content of the IgG2 was approximately five-fold higher than IgG1. When the dose of IgG was adjusted to equalize the antibody content, the clearance ability of the IgG1 and IgG2 was very similar. It is concluded that the two subclasses have a similar clearance ability.

Animals↗

PubMed1989

In-vitro lysis of sensitized Trypanosoma cruzi by platelets: role of C3b receptors.

Incubation of Trypanosoma cruzi bloodstream trypomastigotes (Btrys) with C5-deficient blood in the presence of anti-T. cruzi immune mouse serum (IMS) or its IgG fraction resulted in an immediate formation of small clumps in which one could easily see platelets adhered to the parasites. After 4 h of incubation most of the clumps had disappeared and the number of the parasites was considerably reduced. Twenty-four hours later there were only a few remaining parasites. This same sequence of events was also observed when the parasites were incubated with isolated platelets in presence of IMS or its IgG fraction. When the parasites were incubated with plasma in the presence of IMS or its IgG fraction but in the absence of platelets there was strong agglutination of the parasites but no reduction in their number. Incubation of the parasites with platelets and IMS or its IgG fraction in C3-depleted plasma prevented adherence of the platelets to the parasites and their subsequent lysis. It is concluded that platelets are able to induce in-vitro lysis of the Btrys and that this phenomenon is dependent on the platelet' receptor for C3b.

Agglutination↗

PubMed1989

Role of the mononuclear phagocytic system in the immune and nonspecific clearance of Trypanosoma cruzi bloodstream trypomastigotes.

1. The removal of T. cruzi bloodstream trypomastigotes (BTRYS) from the circulation is mediated mostly by the mononuclear phagocytic system (MPS). In the present study we investigated the nonspecific and the immune clearance of BTRYS in groups of 4 mice whose MPS activity was either enhanced by BCG treatment or depressed by silica treatment. 2. Treatment with BCG resulted in a significant increase in the nonspecific clearance of both carbon particles (100% after 6 min) and BTRYS (60% after 5 min) 28 days after BCG treatment but there was no change in the immune clearance of the parasites. 3. Pretreatment of the animals with silica induced a significant reduction of the colloidal carbon clearance (80% less than control 15 min later) but did not alter the nonspecific or the immune clearance of BTRYS. 4. We conclude that the removal of the opsonized parasites from the circulation is due to a mechanism different from that of the nonspecific clearance.

Animals↗

PubMed1988

Trypanosoma cruzi: advantages of isolating bloodstream trypomastigotes by the carboxy methyl cellulose method.

Bloodstream trypomastigotes were isolated from blood of A/Sn mice 7 d after infection with 10(5) Trypanosoma cruzi Y strain. Red blood cells were removed by centrifugation and hypotonic shock and platelets and leucocytes by passage through a carboxy methyl cellulose column. Binding of trypomastigotes to the resin was prevented by including 10% normal mouse serum in the eluting buffer. In such conditions, more than 90% of the parasites applied to the column were recovered, free of white blood cells and platelets. A comparative study of the pre- and post-separation trypomastigotes showed that both had the same infecting capacity, ability to evade destruction by the complement system, and antigenic profile.

Animals↗

PubMed1988

Role of the antibody Fc in the immune clearance of Trypanosoma cruzi.

Passive transfer of immune serum obtained from mice chronically infected with Trypanosoma cruzi to mice containing circulating bloodstream trypomastigotes induces a very fast clearance of the parasites. Comparison of trypomastigotes clearance in normocomplementemic and C5-deficient mice showed no difference. IgG fraction obtained from immune serum was very efficient at inducing complement-mediated lysis and immune clearance of bloodstream trypomastigotes, whereas its Fc-missing F (ab') 2 fragments, although able to induce lysis, were unable to induce clearance. It is suggested that the immune clearance of bloodstream trypomastigotes is dependent on the antibody Fc region and that complement-mediated lysis is not a prerequisite for elimination of the parasites from circulation.

Animals↗

PubMed1988

Characterization of antibody isotype responsible for immune clearance in mice infected with Trypanosoma cruzi.

Humans and mice chronically infected with Trypanosoma cruzi present a strong humoral immune response mediated by specific antibodies. Passive transfer of homologous immune serum to normal mice containing circulating bloodstream trypomastigotes (Bts) induces a very fast clearance of the parasites. In order to find out the role of the different immunoglobulin classes in the clearance, mice containing a known number of these parasite forms in circulation were injected with total immune serum, IgG-free serum, IgG1, or IgG2 fractions and the speed of removal of the parasites from circulation was determined. The results of these experiments suggest that the immune clearance of T. cruzi is due to antibodies located in the IgG isotype, particularly in the IgG2 subclass.

Animals↗

PubMed1988

Comparison between the antigenic composition of bloodstream and cell culture-derived trypomastigotes of Trypanosoma cruzi.

Antigens of bloodstream and cell culture-derived trypomastigotes of T. cruzi were compared by western blotting using sera of chronic chagasic patients as a source of antibodies. The immunoblots demonstrated that the two forms display extensive homology except for the 85- and 52-kDa bands. These antigens were more strongly stained in culture-derived trypomastigotes. Although the reported differences are not related to major antigens, these results might offer an explanation for previous studies showing that culture-derived trypomastigotes are more antigenic and infective in vitro than bloodstream trypomastigotes.

Animals↗

PubMed1988

Suppression of IgE antibody production by Ascaris suum extract: characterization of suppressive component(s).

Partial characterization of the suppressive component(s) of A. suum extract that is (are) responsible for damping production of IgE antibody to ovalbumin was performed by physical and chemical methods. Digestion of the whole extract with trypsin and chymotrypsin completely abolished the suppressive activity. Oxidation with sodium metaperiodate or heating at 56 degrees C, however, had no effect. These results indicate that the integrity of heat-stable protein(s) present in the crude extract is essential for its suppressive effect. In addition, the carbohydrate moiety does not seem to play an important role in this effect.

Animals↗

PubMed1987

Suppressive effect of an Ascaris suum extract on IgE and IgG antibody responses in mice.

1. A suppressed cytotropic and agglutinating antibody response against ovalbumin was induced in mice immunized with this antigen and an Ascaris suum extract. 2. Suppression of IgE antibody production was abolished by administration of cyclophosphamide or X-irradiation before immunization. In contrast, suppression of homocytotropic IgG1 and heterocytotropic IgG2a antibody responses was considerably resistant to the same treatments. 3. The low levels of IgG agglutinating antibodies also remained unchanged after these treatments. 4. These results indicate that distinct regulatory mechanisms are the targets of suppression induced by A. suum extract in IgE and IgG responses.

Animals↗