Human primary CD4 + T cells activated in the presence of IFN-alpha 2b express functional indoleamine 2,3-dioxygenase.
Indoleamine 2,3-dioxygenase (IDO) is the rate-limiting enzyme in the catabolism of tryptophan. By creating a local microenvironment in which levels of tryptophan are low, IDO-expressing antigen-presenting cells (APC) could regulate T cell activation. This may be relevant to control both viral and bacterial replication as well as neoplastic cell growth. Interferon-alpha (IFN-alpha) is an antiviral cytokine affecting cellular differentiation. In addition, it reduces proliferation of CD4(+) T cells by several molecular mechanisms. To dissect the molecular steps responsible for the INF-mediated antiproliferative activity, we sought to determine whether activated primary CD4(+) T cells in the presence of IFN-alpha would produce IDO. We demonstrate here that IDO mRNA is not present in resting CD4(+) T cells. Stimulation with anti-CD3 plus interleukin-2 (IL-2) induces expression of IDO mRNA (about 2000 copies/150,000 cells), as determined by semiquantitative RT-PCR. When cells were stimulated in the presence of IFN-alpha, expression of IDO mRNA was significantly increased (more than 12,000 copies/150,000 cells). Functional analysis of IDO activity paralleled the results obtained with RT-PCR, demonstrating increased production of active enzyme in CD4(+) T cells stimulated in the presence of IFN-alpha. Our results indicate that IFN-alpha modulates levels of IDO produced by activated CD4(+) T cells. This would likely affect bystander cells by modifying levels of tryptophan in the local microenvironment.
Curreli
S
S
Institute of Human Virology, University of Maryland Biotechnology Institute (UMBI), Baltimore, MD 20201, USA.
Romerio
F
F
Mirandola
P
P
Barion
P
P
Bemis
K
K
Zella
D
D
D001483:Base Sequence; D017252:CD3 Complex / Q000378:metabolism; D015496:CD4-Positive T-Lymphocytes / Q000166:cytology / Q000187:drug effects / Q000201:enzymology* / Q000276:immunology*; D018414:CD8-Positive T-Lymphocytes / Q000166:cytology / Q000187:drug effects / Q000201:enzymology / Q000276:immunology; D002478:Cells, Cultured; D017931:DNA Primers / Q000235:genetics; D015870:Gene Expression; D006801:Humans; D050503:Indoleamine-Pyrrole 2,3,-Dioxygenase; D000077190:Interferon alpha-2; D016898:Interferon-alpha / Q000494:pharmacology*; D007737:Kynurenine / Q000378:metabolism; D008213:Lymphocyte Activation; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014364:Tryptophan / Q000378:metabolism; D014366:Tryptophan Oxygenase / Q000235:genetics* / Q000378:metabolism*
D017252:CD3 Complex; D017931:DNA Primers; D050503:Indoleamine-Pyrrole 2,3,-Dioxygenase; D000077190:Interferon alpha-2; D016898:Interferon-alpha; D012333:RNA, Messenger; D011994:Recombinant Proteins; D007737:Kynurenine; D014364:Tryptophan; D014366:Tryptophan Oxygenase