B7-H3 is a recently identified member of the B7 gene family. Its ubiquitous expression in both lymphoid and nonlymphoid tissues suggests that it could play an important role in the maintenance of self-tolerance. However, the exact function of B7-H3 is still elusive. The purpose of current study is to demonstrate the possible function of soluble mouse B7-H3 for prevention of DC-mediated T cell activation. For this purpose, we established a soluble mouse B7-H3 fusion protein （mB7h3-hIg） eukaryotic expression vector （pmB7h3-hIg） with a C-terminal human IgG1 Fc. A C57BL/6 （B6）-derived dendritic cell line （DC2.4 cells） was used for the establishment of stable transfectants for generation of soluble mB7h3-hIg. Ectopic mB7h3-hIg expression was confirmed by RT-PCR, Western blot and ELISA analyses. A 49.7 kD protein was detected by Western blot from DC2.4 cells transfected with pmB7h3-hlg. It was found that soluble mB7h3-hIg expression has no effect on cell cycling and apoptosis and the expression of CD80 and CD86 of the DC2.4 cells. However, ectopic soluble mB7h3-hIg expression was found to significantly affect the allo-stimulatory capability for DC2.4 cells. DC2.4 cells expressing soluble mB7h3-hIg showed a significant reduced allo-stimulatory capability as compared with the controls determined by MLC. Further studies revealed that soluble mB7h3-hIg could also inhibit IL-2 and IFN-γ, production of allogenic T cells. These results suggested a great potential of soluble B7-H3 for treatment of graft rejection and autoimmume disease. Cellular ＆ Molecular Immunology. 2006;3（3）：235-240.
Junfa XuBaojun HuangPing XiongWei FengYong XuMin FangFang ZhengFeili Gong
