Article

Indoleamine 2,3-dioxygenase tissue distribution and cellular localization in mice: implications for its biological functions.

Department of Pharmacology, Toxicology, and Therapeutics, University of Kansas Medical Center, MS-1018, room KLSIC-4061, 2146 W. 39 Ave., Kansas City, KS 66160, USA.
Journal of Histochemistry and Cytochemistry (impact factor: 2.72). 10/2009; 58(1):17-28. DOI:10.1369/jhc.2009.953604
Source: PubMed

ABSTRACT Earlier studies have suggested that indoleamine 2,3-dioxygenase (IDO) has a wide tissue distribution in mammals. However, detailed information on its cellular localization and also the levels of expression in various tissues is still scarce. In the present study, we sought to determine the cellular localization of IDO and also to quantify the level of its expression in various mouse tissues by using the branched DNA signal amplification assay, Western blotting, and immunohistochemical staining. The highest levels of constitutive IDO expression were found to be selectively present in the caput of epididymis, except for its initial segment. IDO expression was also detected inside the luminal compartment and even in the stereocilia within this region. In the prostate, high levels of IDO were selectively expressed in the capsular cells. In addition, high levels of IDO expression were also selectively detected in certain types of cells in the placenta, spleen, thymus, lung, and digestive tract. Notably, the morphological features of most of the positively stained cells in these organs closely resembled those of antigen-presenting cells. Based on the tissue distribution and cellular localization characteristics of IDO, it is hypothesized that its expression may serve two main functions: one is to deplete tryptophan in an enclosed microenvironment (such as in the epididymal duct lumen) to prevent bacterial or viral infection, and the other is to produce bioactive tryptophan catabolites that would serve to suppress T-cell-mediated immune responses against self-antigens, fetal antigens, or allogeneic antigens, in different situations.

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    Kena A Swanson, Yan Zheng, Kathleen M Heidler, Teruaki Mizobuchi, David S Wilkes
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    F Hirata, O Hayaishi
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Keywords

antigen-presenting cells
 
bioactive tryptophan catabolites
 
capsular cells
 
cellular localization
 
cellular localization characteristics
 
constitutive IDO expression
 
different situations
 
enclosed microenvironment
 
epididymal duct lumen
 
highest levels
 
IDO expression
 
indoleamine 2,3-dioxygenase
 
initial segment
 
luminal compartment
 
morphological features
 
stained cells
 
T-cell-mediated immune responses
 
various mouse tissues
 
viral infection
 
wide tissue distribution
 

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