rmIDO, CF (10 ug)

Background: Indoleamine 2,3-dioxygenase/IDO

Indoleamine 2,3-dioxygenase (IDO) is a heme-containing intracellular dioxygenase that catalyzes the degradation of the essential amino acid L-tryptophan to N formyl kynurenine. This degradation is the first and rate-limiting step of the L-kynurenine pathway (1). IDO expression is induced in macrophages, plasmacytoid dendritic cells (pDC), and microglia by multiple inflammatory stimuli including IFN-g, TNF-a, CpG DNA, HIV-1 Tat protein, microbial infection, or GITR Ligand activation (2-9). It can be expressed by tumor cells, pDC in tumor draining lymph nodes, and MDSC in breast cancer (10-12). IDO expression is critical for the ability of these cells to induce the activation of resting Treg and the support of immune tolerance to apoptotic cell debris (7, 11, 13). These cells also suppress anti-tumor immunity (10, 12), the development of autoimmunity (13), and the replication of Chlamydia, Herpes simplex virus, and measles virus (3, 4, 14). In the absence of IDO function, activation of pDC does not induce immunosuppression but instead triggers IL-6 production and the redirecting of Treg to produce IL-17 (7). Mouse IDO shares 61% and 87% amino acid sequence identity with human and rat IDO, respectively (15).