[Study on immunoregulatory functions of E.coli heat-labil enterotoxin B subunit].
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.
Wang
Jing
J
Institute for Cancer Research School of Life Science and Technology, Xi'an Jiaotong University, Xi'an 710061, China.
Zheng
Jin
J
Yang
Xiao-Feng
XF
Kong
Ling-Hong
LH
Lai
Bao-Chang
BC
Si
Lu-Sheng
LS
Wang
Yi-Li
YL
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
D001427:Bacterial Toxins; D004768:Enterotoxins; D029968:Escherichia coli Proteins