Immunosuppression of NSPC
is not mediated by IDO and not due to induction of apoptosis. (a) NSPCIL-10 and NSPCs express IDO. IDO expression was detected by RT-PCR in spleens, NSPCIL-10 and NSPCs. (b) Inhibition of IDO by 1-MT does not abrogate the immunosuppression mediated by co-culture of NSPCIL-10. C57BL/6 spleen cells were activated with ConA in the presence of neurobasal medium, NSPCIL-10 or NSPCIL-10 and 1-MT. Proliferation was determined by 3H-thymidine incorporation. (c) NSPCIL-10 and NSPCIL-10 culture supernatants do not induce apoptosis in activated spleen cells. C57BL/6 spleen cells were stimulated with ConA in the presence of medium, NSPCIL-10 and NSPCIL-10 culture supernatant. After 24 hours, the frequency of PI+ cells was determined by flow cytometry. 1-MT, 1-methyl-DL-tryptophan; ConA, concanavalin A; IDO, indoleamine 2,3-dioxygenase; IL, interleukin; NSPC, neural stem/progenitor cell; PI, propidium iodide; RT-PCR, reverse transcription polymerase chain reaction.