热不稳定大肠杆菌肠毒素B亚单位免疫调节功能的实验研究

Study on immunoregulatory functions of E.coli heat-labile enterotoxin B subunit

目的 :探讨大肠杆菌热不稳定肠毒素B亚单位 (LTB)的免疫调节功能及其可能的机制。方法 :用SephacrylS 10 0凝胶柱层析纯化LTB蛋白。选用BALB/c小鼠 ,以鸡溶菌酶 (HEL)为抗原 ,经鼻黏膜单独免疫 ,或以不同剂量的LTB为佐剂与HEL共免疫。用ELISA法检测血清和肠分泌液中HEL特异性抗体的水平。用3 H TdR掺入法 ,体外测定LTB蛋白对刀豆蛋白A(ConA)及同种异体抗原介导的淋巴细胞增殖反应的影响。结果 :HEL单独免疫组血清中仅有弱的抗HELIgG ,未检测到抗HELIgA ,且其肠分泌液中亦未见HEL特异性IgA抗体。但加用LTB佐剂的 3个组 ,其血清中抗HELIgG、IgA的水平及肠分泌液中抗HELIgA的水平均显著高于HEL单独免疫组 (P <0 .0 0 1)。体外实验显示 ,LTB可明显抑制ConA及同种异体抗原介导的淋巴细胞增殖反应。结论 :我们制备的LTB蛋白对免疫系统具有双向的调节功能 ,既可作为有效的黏膜佐剂 ,辅佐外来抗原刺激机体产生黏膜免疫应答 ,又具免疫抑制效应 ,有效地抑制淋巴细胞活化。LTB免疫调节功能的发挥 。

AIM: To explore the immunoregulatory functions of Escherichia coli heat labile 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\ 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 .