PubMed · 13018564
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G GARGANI. 1952. [Blocking factor of brucellar agglutination].. https://pubmed.ncbi.nlm.nih.gov/13018564/
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PURPOSE: To clarify the relationships between the degree of lectin-cell binding, cytotoxicity and cytoagglutinating activity of plant-derived lectins in normal lymphocytes and cultured leukemic cell lines. METHODS: Plant lectins with different quaternary structures and saccharide specificity were used: Dolichos biflorus agglutinin (DBA), Soybean agglutinin (SBA) and Wheat germ agglutinin (WGA). The leukemic cell lines used were: Jurkat, MOLT-4, RPMI-8402, HPB-ALL, CCR-HSB-2 and BALL-1 (derived from acute lymphoblastic leukemia); Raji and Daudi (derived from Burkitt's lymphoma); K-562 (derived from myelogenous leukemia). The lectin-cell binding was detected microscopically and fluorimetrically using FITC-conjugated lectins. Cytotoxicity was estimated by the CellTiter-Glo luminescent cell viability assay, and cytoagglutinating activity by a spectrophotometric method. RESULTS: The binding of DBA and SBA to normal lymphocytes was negligible, while their binding to leukemic cells increased markedly with increasing lectin concentration. Analogous results were obtained for WGA. However, it was found that WGA also interacted to a significant degree with normal lymphocytes. The degree of lectin-cell binding increased in the order: DBA<SBA<WGA. The cytoagglutinating activity and cytotoxicity of lectins increased in the same order. DBA did not exhibit a cytotoxic effect against normal or leukemic cells, and showed a poor cytoagglutinating activity only in MOLT-4, CCR-HSB-2 and BALL-1 cells. SBA exhibited poor cytotoxicity against Jurkat, RPMI-8402, HPB-ALL and CCR-HSB-2 cells, but a well-defined cytotoxicity against Raji and Daudi cells. SBA showed poor cytoagglutinating activity in leukemic cells. In contrast, WGA at concentrations higher than 0.05 microM showed high cytotoxicity against all leukemic cell lines tested as well as against normal lymphocytes. WGA also showed a well-expressed cytoagglutinating effect in all cell lines except normal lymphocytes. There was a moderate inverse correlation between cell viability and the velocity of cytoagglutination ( r=-0.56, P<0.001), and a good correlation between cell viability and the degree of lectin-cell binding ( r=-0.75, P<0.001). There was a low positive correlation between the velocity of cytoagglutination and the degree of lectin-cell binding ( r=0.43, P<0.001). CONCLUSION: The results suggest that the lectins that bound most strongly to leukemic cells expressed higher cytotoxic and cytoagglutinating activities.
In this paper the possible involvement of the mannose-receptor on the non-specific recognition and phagocytosis of heat killed yeast cells (Saccharomyces cerevisiae) by gilthead seabream (Sparus aurata L.) head-kidney leucocytes was established by studying the ability of different sugars to inhibit the uptake of the yeast cells by leucocytes. Leucocytes were preincubated for 30min with different concentrations of sugar (alpha-mannan, d-mannose, d-fucose, l-fucose, d-glucose, d-glucosamine and n-acetyl-glucosamine, all of them described as specific ligands of the vertebrate mannose-receptor) and afterwards incubated with FITC-labelled yeast cells for phagocytosis assays. The phagocytic ability (percentage of cells with one or more ingested yeast cells within the total cell population) and capacity (number of ingested yeast cells per cell) of leucocytes was analysed by flow cytometry. The results demonstrate the potential existence of a specific receptor-sugar or receptor-yeast cell binding process, which was saturable, specific and dose-dependent. More specifically, when leucocytes were preincubated with appropriate doses of d-mannose, d- or l-fucose, d-glucose or n-acetyl-glucosamine the phagocytosis of yeast cells by head-kidney leucocytes was partially blocked. Seabream leucocytes were also preincubated with chloroquine, a lysosomotropic drug which downregulates (in a nonspecific manner) the expression of mannose-receptors in mammals, before phagocytosis assays were performed. The results demonstrated that the phagocytosis of yeast was completely blocked by this substance. The overall results seem to corroborate the presence of the mannose-receptor in seabream phagocytes, which is involved in the non-specific binding and phagocytosis of yeast cells by head-kidney leucocytes.
Philasterides dicentrarchi is a histophagous ciliate causing systemic scuticociliatosis in cultured turbot. This study demonstrates that turbot which survive this disease have serum antibodies that recognize ciliary antigens of this ciliate in ELISA and immobilize/agglutinate the ciliate in vitro. Mouse sera raised against ciliary antigens and integral membrane proteins are likewise capable of immobilizing/agglutinating the ciliates, indicating that P. dicentrarchi, like other ciliates, expresses surface immobilization antigens. Furthermore, the antigen agglutinating reaction induces the parasite to shed its surface antigens rapidly, replacing them with others with different specific serology. This antigen shedding and variation response is similar to that detected in other protozoan parasites. Immunization of turbot with ciliate lysate plus adjuvant or with formalin-fixed ciliates induced synthesis of agglutinating antibodies and conferred a degree of protection against challenge infection, suggesting that the response to surface antigens may play an important role in defence against this pathogen, SDS-PAGE and immunoblotting studies indicated the existence of a predominant polypeptide of about 38 kDa in the ciliary antigen and membrane protein fractions, and this may be the principal surface antigen of P. dicentrarchi.