[Preparation of anti-human indoleamine 2,3-dioxygenase polyclonal antibody].

BACKGROUND & OBJECTIVE: Indoleamine 2,3-dioxygenase (IDO), a cytosolic hemoprotein, catalyzes the rate-limiting step in tryptophan catabolism along the kynurenine pathway in mammals, arrests the growth of pathogens, and suppresses T-cell responses, therefore, leads to IDO-dependent tumor immune tolerance. This study was to express and purify His-hIDO fusion protein and to generate rabbit anti-human IDO polyclonal antibody, which was used to analyze IDO expression in tumor cells. METHODS: Human IDO cDNA was cloned into pET30a(+). The recombinant vector pET30a(+)-hIDO was transformed into BL21 after sequencing. The expression of His-hIDO protein was induced by IPTG. The anti-human IDO polyclonal antibody was obtained by immunizing rabbits with purified His-hIDO protein. The quality of the antibody was identified by Western blot. IDO expression in human fibroblast cancer cell line A431 and liver cancer cell line HepG2 induced by interferon-gamma (IFN-gamma) was also analyzed using the antibody. RESULTS: His-hIDO fusion protein was specifically combined with His-probe polyclonal antibody. The rabbit anti-human IDO polyclonal antibody was of high titer with high specificity. It could recognize IDO expression induced by IFN-gamma in A431 and HepG2 cells. CONCLUSION: The rabbit anti-human IDO polyclonal antibody could recognize IDO expression in tumor cells in vitro effectively, therefore, provides a tool to study the role of IDO in tumor immune tolerance.