Abstract: Objective To study the effects of dead macrophage infected by B. suis S2 to prime T cell immune response. Methods Macrophage was infected for 1 h by B. suis S2 in vitro and the normal macrophge acted as control, and was cultured with serum-free medium for 5 d untill the cell completly dead. The dead macrphage was co-cultured with murine bone marrow-derived dendritic cells (BMDC) for 24 h. The IL-12, TNF-αsecreted by BMDC were detected with indirected ELISA. Meanwhile the BMDC was co-cultured with T cells, and the IFN-γcontent in the culture supernatant was detected by ELISA. Results Both normal dead macrophages and B. suis S2 infected dead macrophages could induce BMDC TNF-αsecretion and the TNF-αsecretion of BMDC in B. suis S2 infected group was signiifcantly increased than that of control group(P<0.05), but IL-12 was not produced. The levels of IFN-γof T cell in B. suis S2 infected group were signiifcantly higher than those of control group at 24 h, 48 h and 72 h (P<0.05). Conclusion The dead macrophage infected by B. suis S2 can activvate DC to secret TNF-αand present antigen to T cell and result in T cell IFN-γsecretion.

Key words: Brucella suis, macrophage, dentritic cell, T cell