Biomedical subjects

N Buonavista

Publications and source records attributed to N Buonavista.

4 recordsLinked to original sources

PubMed1995

Identification of a major T cell immunogen in the anti-schistosome response of adult residents in an area endemic for Schistosoma mansoni.

Vaccine-induced immunity to Schistosoma mansoni infection depends on the specific priming of certain T cell subsets and on the recall of this response by natural infections months or years after vaccine administration. Thus, those schistosome proteins that activate T cells in individuals stimulated by natural infections are potential candidate vaccine antigens. In the present study, we identified and purified one such T cell-stimulating antigen and evaluated its immunological properties in subjects living in an area endemic for Schistosoma mansoni. Chromatography fractions (gel filtration, followed by ion exchange chromatography) of soluble extracts of schistosomula were screened for their ability to stimulate schistosome-specific T cell clones derived from a subject sensitized by natural infection. A fraction stimulating most clones was identified and characterized. A few nanograms of this fraction, containing a major 9-10-kDa component, stimulated the T helper cells of most adults living in an endemic area of Brazil, and was able to trigger a strong cutaneous immediate hypersensitivity reaction. In contrast, children reacted weakly to this antigen preparation both in blastogenesis and in skin tests, although they mounted a significant reaction to crude larval antigen preparations. In conclusion, this work identifies a schistosomula antigen that induces a strong T cell response in adults sensitized by natural infections. This T cell response develops gradually in children and adolescents, is apparently not restricted by the HLA haplotypes common in the study area, and allows the production of parasite-specific IgE antibodies. Thus, this T cell response has some features of the immune response that is believed to protect chronically exposed humans from reinfection.

Adult↗

PubMed1994

Programmed cell death in Dictyostelium.

Programmed cell death (PCD) of Dictyostelium discoideum cells was triggered precisely and studied quantitatively in an in vitro system involving differentiation without morphogenesis. In temporal succession after the triggering of differentiation, PCD included first an irreversible step leading to the inability to regrow at 8 hours. At 12 hours, massive vacuolisation was best evidenced by confocal microscopy, and prominent cytoplasmic condensation and focal chromatin condensation could be observed by electron microscopy. Membrane permeabilization occurred only very late (at 40-60 hours) as judged by propidium iodide staining. No early DNA fragmentation could be detected by standard or pulsed field gel electrophoresis. These traits exhibit some similarity to those of previously described non-apoptotic and apoptotic PCD, suggesting the hypothesis of a single core molecular mechanism of PCD emerging in evolution before the postulated multiple emergences of multicellularity. A single core mechanism would underly phenotypic variations of PCD resulting in various cells from differences in enzymatic equipment and mechanical constraints. A prediction is that some of the molecules involved in the core PCD mechanism of even phylogenetically very distant organisms, e.g. Dictyostelium and vertebrates, should be related.

Animals↗

PubMed1992

Molecular linkage of the human CTLA4 and CD28 Ig-superfamily genes in yeast artificial chromosomes.

CD28 and CTLA4 are structurally homologous single-V-domain molecules of the Ig superfamily, the genes of which comap on the same chromosomal bands in mouse and man. Using polymerase chain reactions, we isolated six yeast artificial chromosome (YAC) clones positive for CTLA4 and/or CD28 from a human-DNA-containing YAC library. Two double-positive clones, 365 and 550 kb long, respectively, were further studied. Detailed restriction enzyme maps showed that one of these YACs was nested in the other, that they both bore the same CD28- and CTLA4-hybridizing fragments, that similar fragments were seen in genomic DNA, and that the distance between the CD28 and CTLA4 genes was at most 150 kb and at least 25 kb. A CpG island was found between these genes. These results provide a high-resolution estimate of the physical distance between the CD28 and CTLA4 genes and constitute a basis for the isolation of neighboring structures.

Abatacept↗

PubMed1992

CTLA-4 and CD28: similar proteins, neighbouring genes.

Subtractive cloning and screening yielded a cDNA clone corresponding to a molecule expressed in activated T cells, called CTLA-4. At the protein level, CTLA-4, a single-V-domain member of the immunoglobulin superfamily, was found very homologous to the lymphocyte activation molecule CD28. In particular, the hinge region included the hexamer MYPPPY, completely conserved for both molecules and in mice and humans. By immunizing mice with a human CTLA-4 peptide, an anti-CTLA-4 monoclonal antibody (MAb) was obtained, which enabled to establish the MW of the protein (26 and 40 kDa under reduced and non-reduced conditions respectively) and its preliminary tissue distribution. Also, CTLA-4 and CD28 were very similar at the message and at the gene structure level. The corresponding genes had previously been found to co-map on mouse chromosome IC and on human chromosome 2q33. We show that they can be found on the same yeast artificial chromosomes bearing human genomic DNA, and that they are 25 to 150 kb apart. These marked homologies and gene proximity strongly suggest that CTLA-4 and CD28 are the direct products of a duplication event, and raise the question of the function of CTLA-4.

Abatacept↗