Regulation of IgE response by employing recombinant IgE-binding factor

In order to analyze the角色of soluble Fc receptor II （Fc RII/CD23）attempts were made to produce recombinant soluble Fc RII as secretory protein. Several plasmidconstructs containing soluble receptor sequence Only a chimeric gene containing thesequences encoding IL-6 signal peptide and the soluble moiety of Fc RII could be expressed inXenopus leavis oocytes and CHO cellsresulting in the secretion of soluble FC RII. Neuraminidase treatment reduced the MW of the product，suggesting that soluble receptor might be 0-glycosylated. Furthermore，this recombinant product as well as natural soluble receptor derived from a human B cell line couldbind both human IgE and two different monoclonal anti-Fc RII antibodies. However，the recombinant soluble Fc RII did not display any B cell growth promoting activity.Subsequently，the function of soluble Fc RII in effector phase of IgE-mediated hypersensitivity was studied.Soluble Fc II inhibited IgE-rosette formation of Fc RII^+ monocytic cell line, U937，and eosinophilic cell line, EoL-3，in a dose dependent fashion （in the presence of 30g /ml soluble Fc II）60-70% of IgE-rosette formation was suppressed . Soluble Fc II also inhibited Fc RII-mediated o_2生产活动macrophages as determined by nitro blue tetrazolium (NBT) test. furthermore，soluble Fc RII competitively inhibited the binding of IgE to basophils，500 g/ml of soluble Fc RII showed 60-85% inhibition.这些结果indicate that soluble Fc RIImay regulate the effector phase of IgE-mediated hypersensitivity. the ability of soluble Fc RII toinhibit histamine release from basoplils is investigation。

In order to analyze the role of soluble Fc receptor II (Fc RII/CD23), attempts were made to produce recombinant soluble Fc RII as a secretory protein. Several plasmid constructs containing soluble receptor sequence were prepared. Only a chimeric gene containing the sequences encoding IL-6 signal peptide and the soluble moiety of Fc RII could be expressed in Xenopus leavis oocytes and CHO cells, resulting in the secretion of soluble FC RII. Neuraminidase treatment reduced the MW of the product, suggesting that soluble receptor might be 0-glycosylated. Furthermore, this recombinant product as well as natural soluble receptor derived from a human B cell line could bind both human IgE and two different monoclonal anti-Fc RII antibodies. However, the recombinant soluble Fc RII did not display any B cell growth promoting activity.Subsequently, the function of soluble Fc RII in effector phase of IgE-mediated hypersensitivity was studied. Soluble Fc II inhibited IgE-rosette formation of Fc RII^+ monocytic cell line, U937, and eosinophilic cell line, EoL-3, in a dose dependent fashion (in the presence of 30 g/ml soluble Fc II, 60-70% of IgE-rosette formation was suppressed). Soluble Fc II also inhibited Fc RII-mediated O_2 ・ production of activated macrophages as determined by nitro blue tetrazolium (NBT) test. furthermore, soluble Fc RII competitively inhibited the binding of IgE to basophils, and 500 g/ml of soluble Fc RII showed 60-85% inhibition. These results indicate that soluble Fc RII may regulate the effector phase of IgE-mediated hypersensitivity. The ability of soluble Fc RII to inhibit histamine release from basoplils is under investigation.