title: Galactoside-specific plant lectin, Viscum album agglutinin-I induces enhanced proliferation and apoptosis of murine thymocytes in vivo.
abstract: Galactoside-specific plant lectin, Viscum album agglutinin-I (VAA-I) has been shown to act as a biomodulator with proinflammatory and apoptosis-inducing effects, however its cellular targets and mechanism of immunobiological action in vivo are less well understood. Therefore, in the present work the short- and long-term in vivo effects of VAA-I on thymocyte subpopulations and peripheral T cells were tested using a murine (Balb/c) model. Cell surface CD4/CD8 staining and flow cytometry allowed us to follow the changes of thymocyte subpopulations: CD4-CD8- double negative (DN), CD4+CD8+ double positive (DP), CD4+ or CD8+ single positive (SP) and mature peripheral T cells after single or repeated injections with low doses of VAA-I. The apoptosis of the cells was detected by flow cytometry using propidium iodide (PI) and Annexin V staining. To detect the short-term effects of the lectin, the animals were investigated 24 h after a single injection of 1 or 30 ng/kg body weight (BW) VAA-I+/-1 mg/kg Dexamethasone (DX). The total number of mature CD8+ SP thymocytes increased significantly with an enhancement of the ratio of apoptotic cells. In contrast, in the blood samples an elevated CD4/CD8 ratio was found. In the next trial, Balb/c mice were treated twice weekly with 1 or 30 ng/kg VAA-I+/-1 mg/kg DX for 3 weeks. The total cell count of thymocytes showed significant increases after both doses of VAA-I, but an elevated percentage of apoptotic cells was found only after treatment with 30 ng/kg VAA-I. SP thymocytes revealed higher increases in lectin-induced apoptosis than DN or DP cells. In addition, both lectin doses significantly inhibited the DX-induced reduction of all thymocyte subpopulations investigated. In conclusion, our data suggest that VAA-I is able to modulate the maturation of thymocytes in vivo.
authors.affiliation: Department of Immunology and Biotechnology, Faculty of Medicine, University of Pécs, Szigeti út 12, H-7643 Pécs, Hungary.
authors.forename: Tibor
authors.initials: T
authors.lastname: Hajtó
authors.forename: Timea
authors.initials: T
authors.lastname: Berki
authors.forename: Ferenc
authors.initials: F
authors.lastname: Boldizsár
authors.forename: Péter
authors.initials: P
authors.lastname: Németh
mesh_terms: D000276:Adjuvants, Immunologic / Q000494:pharmacology*; D000818:Animals; D000893:Anti-Inflammatory Agents / Q000494:pharmacology; D017209:Apoptosis; D016516:CD4-CD8 Ratio; D002452:Cell Count; D002455:Cell Division / Q000187:drug effects / Q000276:immunology; D003907:Dexamethasone / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005260:Female; D005434:Flow Cytometry; D008213:Lymphocyte Activation / Q000187:drug effects / Q000276:immunology; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D028321:Plant Preparations / Q000494:pharmacology*; D010940:Plant Proteins; D054788:Ribosome Inactivating Proteins; D054790:Ribosome Inactivating Proteins, Type 2; D016176:T-Lymphocyte Subsets / Q000187:drug effects* / Q000276:immunology / Q000473:pathology; D013950:Thymus Gland / Q000166:cytology / Q000187:drug effects; D014118:Toxins, Biological / Q000494:pharmacology*
chemical_list: D000276:Adjuvants, Immunologic; D000893:Anti-Inflammatory Agents; D028321:Plant Preparations; D010940:Plant Proteins; D054790:Ribosome Inactivating Proteins, Type 2; D014118:Toxins, Biological; C488865:VAA-I protein, Viscum album; C009674:ribosome inactivating protein, Viscum; D003907:Dexamethasone; D054788:Ribosome Inactivating Proteins