Differential Regulation of Interleukin (IL)-12 p35 and p40 Gene Expression and Interferon (IFN)-γ–primed IL-12 Production by IFN Regulatory Factor 1

Abstract

Interleukin (IL)-12 is a heterodimeric cytokine consisting of the p40 and p35 chains encoded on separate chromosomes. Coordinated expression of the two constituent genes is crucial for appropriate immune responses in timing, location, and magnitude. Interferon (IFN)-γ priming of IL-12 production by macrophages represents an important physiological process in vivo for escalated cellular response to microbial infections. We provide evidence that IFN regulatory factor (IRF)-1–deficient macrophages have a selective impairment in mRNA synthesis of IL-12 p35 but not the p40 gene, and a strong deficiency in the production of IL-12 p70 but not p40. We demonstrate that the levels of IL-12 p35 protein stimulated by IFN-γ and lipopolysaccharide (LPS) correspond to those of its mRNA, and that the nuclear factor κB signaling pathway is essential for the induction of IL-12 p35 transcription by LPS. IRF-1 plays a major role in the transcriptional activation of the IL-12 p35 gene, but not of the p40 gene, by physically interacting with an inverted IRF element within the IL-12 p35 promoter upon IFN-γ activation. Moreover, IRF-1–mediated transcriptional activation of the p35 promoter requires the cooperation of two adjacent Sp1 elements. Thus, IRF-1 acts as a critical component of IFN-γ signaling in the selective activation of IL-12 p35 transcription in synergy with LPS-mediated events.

Down-regulation of dendritic cell signaling pathways by Leishmania amazonensis amastigotes

“…IL-12 is a proinflammatory cytokine, and the expression of its two subunits, p40 and p35, are known to be transcriptionally regulated by NF-κB and IRFs (Grumont et al, 2001;Liu et al, 2003;Maruyama et al, 2003;Masumi et al, 2002). Cameron et al found that the inhibition of LPS-induced IL-12 production in L. mexicana amastigote-infected MΦs was due to the degradation of IκB and NF-κB by amastigotes-derived cysteine peptidase B (Cameron et al, 2004).…”

Deficient IL-12p70 secretion by dendritic cells based on IL12B promoter genotype

“…1 These chains are encoded by genes on different chromosomes and their production can be regulated independently. 2,3 IL-12 is produced by a number of cell types, including macrophages, neutrophilic granulocytes and dendritic cells (DCs). DCs may be the most important source of IL-12.…”

Synergistic Activation of Interleukin-12 p35 Gene Transcription by Interferon Regulatory Factor-1 and Interferon Consensus Sequence-binding Protein

“…In this work, we sought to elucidate how ICSBP regulates IL-12 p35 gene transcription by first examining the response of the human IL-12 p35 promoter to the effects of ICSBP in a well established transient transfection system in RAW cells (12). Fig.…”

“…Previous studies by us and others have revealed an intimate relationship between IRF-1, ICSBP, and IL-12 in that IRF-1 acts as a critical component of IFN-␥ signaling in the selective activation of the IL-12 p35 transcription (12) in synergy with LPS-mediated events (13,14) and that IRF-1 and ICSBP cooperatively regulate the transcription of IL-12 p40 gene in IFN-␥-amplified IL-12 production (15,16). In this work, we show that ICSBP and IRF-1, activated primarily by IFN-␥, also cooperate in their transcriptional activation of the IL-12 p35 gene by directly binding to a specific site in the human IL-12 p35 promoter.…”