Interleukin-4 inhibits indoleamine 2,3-dioxygenase expression in human monocytes

T. Musso, G. L. Gusella, A. Brooks, D. L. Longo, L. Varesio

Research output: Contribution to journalArticlepeer-review


Indoleamine 2,3-dioxygenase (IDO), a flavin-dependent enzyme that catalyzes the conversion of tryptophan to kynurenine, is induced in peripheral blood mononuclear cells by interferon-γ (IFNγ). Interleukin-4 (IL-4) is a cytokine that modulates the functional properties of monocytes/macrophages, and we investigated the effects of IL-4 on IDO. We showed that IL-4 inhibited the induction of IDO mRNA and IDO activity by IFNγ in human monocytes. The inhibitory effect was evident with as little as 2 U/mL of IL-4. These results provide the first evidence that a cytokine can provide a negative signal for IDO expression and that IL-4 can influence the catabolism of tryptophan.

Original languageEnglish
Pages (from-to)1408-1411
Number of pages4
Issue number5
Publication statusPublished - Mar 1 1994

ASJC Scopus subject areas

  • Hematology

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