In vitro anti-tumor immune mechanism of nasopharyngeal carcinoma bispecific anti-idiotype antibody.

OBJECTIVE:To compare the in vitro antitumor immune responses induced by bivalent bispecific anti-idiotype antibody G22-I50 and monovalent anti-idiotype antibody G22 and I50, and explore its possible mechanism. METHODS:Proteins G22-I50, G22, and I50 were induced and identified by Western blot and ELISA. Peripheral blood monoclear cells (PBMC) were isolated and stimulated with G22-I50, G22, and I50 anti-idiotype antibodies, respectively. MTT assay and LDH release test were employed to examine the proliferation and cytotoxicity of the PBMC. The levels of IFN-gamma, IL-2, and IL-4 in the supernatant were detected by ELISA and changes of T lymphocyte subsets were determined by flow cytometry. RESULTS:Western blot showed that G22-I50, G22, and I50 had specific binding capabilities to FC2 (Ab1). The activities of G22-I50, G22, and I50 had recovered and these proteins could be used in the in vitro study. The proliferation and cytotoxicity of the PBMC stimulated with G22-I50 were significantly higher than those stimulated with G22 or I50. The level of IFN-gamma and IL-2 in the culture supernatant of the PBMC stimulated with G22-I50 was higher than that in the G22 or I50 group, but the level of IL-4 did not increase. Compared with the G22 or I50 group, the proportion of CD4(+) and CD8(+) T cells and CD4(+)/CD8(+) ratio significantly increased, and the proportion of CD4(+)CD25(+) T cells significantly decreased in the PBMC stimulated with G22-I50. CONCLUSION:G22-I50 has more potent immunogenicity and would enhance specific antitumor effect which might relate to improving PBMC proliferation, inducing the secretion of Th1 type cytokines, activating CD8(+)T cells, and suppressing the expression of CD4(+)CD25(+) T cells.