title: Effects of in vivo neuraminidase on the regulation of erythropoiesis. II: Modulation of erythroid colony formation by thymic regulatory cells.
abstract: Effects of the enzyme vibrio-cholerae neuraminidase (VCN) on the marrow-derived erythropoietic progenitor CFU-E and thymic regulatory cells were examined in vitro 1 and 24 h after i.v. injection of the enzyme. An in vivo enzymatic modification of bone marrow and thymic helper regulatory cell function occurs within 1 h after i.v. injection of VCN and results in suppression of both CFU-E colony formation and thymic helper cell function. These inhibitory effects of neuraminidase, however, are no longer detectable by 24 h after injection. More importantly, these inhibitory effects can be reversed by adding thymocytes from control animals to cocultures of enzymatically modified marrow or thymic regulatory cells. These findings: 1) suggest that regulatory cells from the bone marrow and thymus may be enzymatically modified in vivo in a reversible manner, suggesting a noncytotoxic effect of the enzyme on accessory cells, and 2) confirm the importance of sialic acid for the helper function but not for the suppressor function of thymocytes and CFU-E colony formation in vitro.
authors.affiliation: Department of Experimental Hematology, Johns Hopkins University School of Medicine, Baltimore, Maryland.
authors.forename: V F
authors.initials: VF
authors.lastname: La Russa
authors.forename: L L
authors.initials: LL
authors.lastname: Sensenbrenner
authors.forename: S J
authors.initials: SJ
authors.lastname: Sharkis
mesh_terms: D000818:Animals; D001853:Bone Marrow; D002455:Cell Division / Q000187:drug effects; D003114:Colony-Forming Units Assay; D004900:Erythroblasts / Q000187:drug effects / Q000502:physiology*; D004920:Erythropoiesis / Q000187:drug effects*; D005260:Female; D007275:Injections, Intravenous; D051379:Mice; D009439:Neuraminidase / Q000008:administration & dosage*; D013601:T-Lymphocytes / Q000187:drug effects / Q000502:physiology*; D014734:Vibrio cholerae / Q000201:enzymology
chemical_list: D009439:Neuraminidase