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G Vicari

Publications and source records attributed to G Vicari.

36 records · Page 2Linked to original sources
PubMed1976

An improved method for synthesising omega-stearoyldextran for the detection of plaque forming cells specific for the alpha-(1 replaces 6) determinant.

A method for synthesising omega-stearoyldextran for the detection of plaque forming cells specific for the alpha-(1 replaces 6) determinant is described. The omega-stearoyl derivative is obtained by reacting dextran with phenylboronic acid to give a 2,4-phenylboronate, which can be subsequently esterified in a pyridine solution with stearoyl chloride. Four different preparations of omega-stearoyldextran with increasing content of stearoyl were obtained. Chemical and immunochemical properties of these compounds are given.

Animals↗
PubMed1975

Influence of molecular structure on the tolerogenicity of bacterial dextrans. I. The alpha1--6-linked epitope of dextran B512.

Native dextran B512 is a near-linear glucose polymer with 96 per cent alpha1--6 and 4 per cent alpha1--3 linkages and a molecular weight (mol. wt) of 8 X 10(7). Sheep RBC sensitized with its O-stearoyl derivative (prepared by a modified method) have been used satisfactorily in direct PFC assays. B512 immunizes BALB/c mice optimally with doses of 1--10 mug and produces B-cell tolerance with 1 mg upwards. The specificity of the response determined by PFC inhibition analysis, is directed towards an alpha1--6-linked epitope. High dose tolerance is not preceded by immunity and is stable on cell transfer to irradiated recipients in which responsiveness becomes perceptible after 4--6 weeks. Progressive depolymerization of this polysaccharide reduces immunogenicity and tolerogenicity, both of which are extinguished when the mol. wt falls to 2 X 10(4). Optimal immunization with B512 is succeeded by partial tolerance (previously characterized by analogous levan experiments as a B-cell exhaustion process). The tolerance threshold dose of B512 is reduced 1000-fold during immunosuppression with cyclophosphamide. PFC inhibition studies supported the contention that tolerogenicity of polysaccharides is influenced by their overall binding capacities. A direct relationship between inhibitory and tolerogenic activities was found both with B512 fractions of varying mol. wt and with heterologous dextrans. The similarities between B512 and levan argue against the association of a highly branched structure with greater tolerogenicity. The effect of reducing the percentage of alpha1--6 linkages in dextrans suggests, however, that epitope density probably plays a contributory role in determining the outcome of interaction between polysaccharides and B cells.

Animals↗
PubMed1975

Influence of molecular structure of the tolerogenicity of bacterial dextrans. III. Dissociation between tolerance and immunity to the alpha1--6- and alpha1--3-linked epitopes of dextran B1355.

Dextran B1355 induces a direct PFC response detectable with dextran B512-sensitized red cells which is directed towards an alpha1--6-linked glucose epitope. This response is distinguishable from the alpha1--3-linked specificity assayed by homologous sensitization in that: (a) it is totally suppressed in donors previously rendered tolerant of B512; (b) the PFC are sensitive to inhibition by B512 and isomaltohexaose. The alpha1--6 epitope of B1355 is less immunogenic in BALB/c mice than that with alpha1--3 linkage, inducing a lower amplitude of response and requiring a 100-fold greater minimal dose, while conversely, it is the more effective tolerogen. No alpha1--6-specific response develops in 50 per cent of mice given 10 mg of B1355 and all become totally unresponsive within 14 days. This tolerant state remains stable when spleen cells are transferred to irradiated recipients. By comparison, parallel depression of the alpha1--3 response is not great and rapidly lost by similar transfer. No correlation was observed between the levels of alpha1--6 suppression and alpha1--3 response induced by 10 mg of B1355 in individual mice. The dissociative aspects of the responses to these two epitopes present on the same molecule are discussed in relation to some current theories of B-cell tolerance induction. It is argued that the present findings are contrary to those models which attribute a causal role to mitogenic overstimulation or failure to generate an extrinsic 'second signal'.

Animals↗
PubMed1974

An evaluation of an agar gel diffusion test with crude and purified antigens in the diagnosis of hydatid disease.

The sensitivity of the indirect haemagglutination test for the diagnosis of hydatid disease, although high, is insufficient. Agar gel diffusion tests for the diagnosis of this disease have not received much attention in the past and have been considered unsatisfactory. The authors propose such a test and evaluate its results in comparison with those of the indirect haemagglutination test.

Agar↗
PubMed1971

Immunochemical studies on blood groups. XLVII. The I antigen complex--precursors in the A, B, H, Lea, and leb blood group system--hemagglutination-inhibition studies.

A partially purified blood group-like substance obtained from milk showed I activity with 2 of 21 anti-I sera. With these antisera, certain human ovarian cyst substances considered to be precursors of the A, B, H, Le(a), and Le(b) substances also showed I activity comparable to the milk material. Strong I activity could be produced by one-stage periodate oxidation and Smith degradation of human ovarian cyst A and B substances, or of hog mucin A + H substance, or by mild acid hydrolysis of human saliva or ovarian cyst blood group B substance. The two sera indicate that I specificity appears at intermediate stages in the biosynthesis of the A, B, H, Le(a), and Le(a) substances. Anti-I sera differ strikingly in their specificities, indicating substantial heterogeneity of the I determinants.

ABO Blood-Group System↗
PubMedDate not supplied

Detection of anti-HIV antibodies in preparations of human immunoglobulins. A collaborative group study.

This paper reports the results of a study organized by the Istituto Superiore di Sanità (Rome, Italy) and carried out in collaboration with several national laboratories. Its aim was to ascertain whether diagnostic kits for detecting anti-HIV antibodies in human serum can also be used to detect the same antibodies in human immunoglobulins. Thirty-three lots of immunoglobulins supplied by six pharmaceutical companies present in Italy were examined using different procedures. On the basis of the results of this study it can be concluded that i. anti-HIV antibodies can be detected in immunoglobulins by means of commercial reagents; ii. a preliminary dilution of immunoglobulin samples should not be made; iii. Western blot method appears to be the 'reference' test; however, competitive EIA tests are equally valuable if a negative control made up of anti-HIV-negative Igs is employed; iv. Igs examination for anti-HIV antibody represents an indirect control on a correct donors' screening procedure.

Blotting, Western↗
PubMedDate not supplied

Detection of antibodies against Echinococcus granulosus major antigens and their subunits by immunoblotting.

An immunoblot assay was tested to evaluate its ability to diagnose human hydatidosis and to analyse the reactivity of hydatid patients' sera with the subunits of the 2 major Echinococcus granulosus antigens (5 and B). In all, 308 sera were examined: 166 sera from patients with clinically diagnosed hydatidosis, 100 sera from healthy control subjects, and 42 sera from patients with diseases other than hydatidosis. The sensitivity of the method was 90%, as compared to 78% with the immunoelectrophoresis/double diffusion test for antigen 5. No reactivity was found with 15 sera from patients with schistosomiasis, 7 sera from patients with trichinellosis, or 20 sera from patients with non-parasitic diseases. Analysis of serum reactivities showed the presence in all positive sera of antibodies directed against the 39 kDa molecule of the antigen 5 complex. A lower reactivity (55% of all hydatid sera) was observed with the subunits of the antigen B complex.

Animals↗