Elevated Expression of Brain Indoleamine 2,3-Dioxygenase is Associated with Early Mouse Development

Indoleamine 2,3-Dioxygenase (IDO) catalyzes the oxidative degradation of the essential amino acid L-tryptophan at the initial and rate-limiting step of the kynurenine pathway. Although IDO via L-tryptophan depletion may suppress the growth of various pathogens, its immunomodulatory features and the cascade kynurenine pathway catabolites may contribute, by reducing immune responses of T cells, to the development of immunodeficiency observed in diseases such as HIV, autoimmune disorders and cancer. This study has focused on the IDO activity change in mice and discovered a linear relationship between the mouse brain IDO activity increase and the logarithmic function of mouse age in the early development of the healthy mice up to 8 weeks. This relationship may reflect the increase in infectious pathogen inhibition capability as well as immunologic tolerance through the early development of mice. This finding enhances our understanding of the IDO function in the mouse brain and may facilitate the mouse model selection for IDO research and related drug development.