title: [Study on immunoregulatory functions of E.coli heat-labil enterotoxin B subunit].
abstract: OBJECTIVE
  To explore the immunoregulatory functions of Escherichia coli heat-labil enterotoxin B subunit(LTB) and its possible mechanism.
  
  
  METHODS
  The rLTB in engineering bacteria VSP60 was purified by Sephacryl S-100 gel filtration chromatography. BALB/c mice were immunized nasally with hen egg lysozyme(HEL) alone or in combination with various doses of LTB. After three times of immunization, specific anti-HEL IgG and IgA levels in serum and small intestinal secretory fluid were determined by ELISA. The effects of LTB on alloantigen- and ConA- mediated lymphocyte proliferation reactions were measured by (3)H-TdR incorporation assay.
  
  
  RESULTS
  Very weak serum anti-HEL IgG response and no IgA response were detected in mice immunized with HEL alone. However, levels of both serum anti-HEL IgG, IgA and intestinal secretory fluid IgA in mice immunized with various doses of HEL+LTB were higher than those in mice immunized with HEL alone(P<0.001). In-vitro, LTB could obviously inhibit the lymphocyte proliferation induced by mitogen and alloantigen.
  
  
  CONCLUSIONS
  The effects of LTB protein on immnune system may be bi-directional. LTB is not only a powerful mucocal immunoadjuvant in-vivo, but also a potent immunosuppressive agent In-vitro.
authors.affiliation: Institute for Cancer Research School of Life Science and Technology, Xi'an Jiaotong University, Xi'an 710061, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Wang
authors.forename: Jin
authors.initials: J
authors.lastname: Zheng
authors.forename: Xiao-Feng
authors.initials: XF
authors.lastname: Yang
authors.forename: Ling-Hong
authors.initials: LH
authors.lastname: Kong
authors.forename: Bao-Chang
authors.initials: BC
authors.lastname: Lai
authors.forename: Lu-Sheng
authors.initials: LS
authors.lastname: Si
authors.forename: Yi-Li
authors.initials: YL
authors.lastname: Wang
mesh_terms: D000818:Animals; D001427:Bacterial Toxins / Q000276:immunology; D004768:Enterotoxins / Q000276:immunology; D004926:Escherichia coli / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000276:immunology; D006358:Hot Temperature
chemical_list: D001427:Bacterial Toxins; D004768:Enterotoxins; D029968:Escherichia coli Proteins