Indoleamine 2,3-dioxygenase is differentially expressed by different white blood cell populations of rhesus macaques (Macaca mulatta)

Background Indoleamine 2,3‐dioxygenase (IDO) is involved in immune processes such as transplant and fetal rejection, autoimmunity, cancer, and infection; however, its expression in rhesus macaques has not been fully addressed. Methods Indoleamine 2,3‐dioxygenase mRNA and protein in the white blood cells (WBCs) of Chinese rhesus macaques were examined by RT‐PCR, western blotting, real‐time RT‐PCR, and flow cytometry. Results Both IDO protein and mRNA could be readily detected in WBCs or peripheral blood mononuclear cells (PBMCs) of normal rhesus macaques. IDO+ cell frequency was the highest among CD14+ mononuclear cells, followed by CD56+ cells and DCs. No difference in the frequency of IDO+ cells between CD4+ and CD8+ T cells; however, Th17 cells have higher frequency of IDO+ cells than Th1 cells, with Th2 cells the lowest. Toll‐like receptor (TLR) stimulation significantly increased IDO protein level in CD14+, CD56+, CD1c+, CD11c+, and CD123+ myeloid cells. Conclusion Rhesus macaques express IDO differentially in their leukocyte subsets and are suitable for IDO‐related pathophysiological studies.