title: Immunosuppressive factor from Actinobacillus actinomycetemcomitans down regulates cytokine production.
abstract: A cytoplasmic soluble fraction of Actinobacillus actinomycetemcomitans Y4 was isolated and characterized as suppressing mitogen-stimulated proliferation of and cytokine production by C3H/HeN mouse splenic T cells. This factor, designated suppressive factor 1 (SF1), was isolated from the supernatant of sonicated whole bacteria and purified by Q-Sepharose Fast Flow column chromatography, DEAE-Sepharose Fast Flow column chromatography, hydroxyapatite high-pressure liquid chromatography (HPLC), and Protein Pack 300 & 125 gel filtration HPLC. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis revealed that the purified SF1 migrated as a single band corresponding to a molecular mass of 14 kDa. This molecule was protease labile, heat resistant, and noncytotoxic. N'-terminal sequence analysis revealed no homology with any known peptides of periodontopathic bacteria or with any host-derived growth factors. Purified SF1 suppressed the proliferation of mouse splenic T cells which had been stimulated with concanavalin A, as well as suppressing the production of interleukin-2 (IL-2), gamma interferon, IL-4, and IL-5 from CD4+ T cells as 0.1 microgram/ml or more. These data suggest that SF1 produced by the periodontal pathogen A. actinomycetemcomitans functions as a virulence factor by down regulating T-cell proliferation and cytokine production at local defense sites.
authors.affiliation: Department of Microbiology, Nihon University School of Dentistry at Matsudo, Chiba, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Kurita-Ochiai
authors.forename: K
authors.initials: K
authors.lastname: Ochiai
mesh_terms: D016976:Aggregatibacter actinomycetemcomitans / Q000276:immunology*; D000595:Amino Acid Sequence; D000818:Animals; D001426:Bacterial Proteins / Q000302:isolation & purification / Q000494:pharmacology*; D015496:CD4-Positive T-Lymphocytes / Q000187:drug effects; D016207:Cytokines / Q000096:biosynthesis*; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation; D005260:Female; D008213:Lymphocyte Activation / Q000187:drug effects; D051379:Mice; D008809:Mice, Inbred C3H; D008969:Molecular Sequence Data; D017421:Sequence Analysis; D013601:T-Lymphocytes / Q000187:drug effects*
chemical_list: D001426:Bacterial Proteins; D016207:Cytokines