Human CD4+CD25+Foxp3+ Regulatory T Cells Do Not Constitutively Express IL-35

Abstract

EBV-induced gene 3 (EBI3) can associate with p28 to form the heterodimeric cytokine IL-27, or with the p35 subunit of IL-12 to form the EBI3/p35 heterodimer, recently named IL-35. In mice, IL-35 has been shown to be constitutively expressed by CD4+CD25+Foxp3+ regulatory T cells (Treg cells) and suggested to contribute to their suppressive activity. In this study, we investigated whether human Treg cells express IL-35. Double-staining analysis of human thymuses showed that neither Foxp3+ nor CD25+ cells coexpressed EBI3. Similarly, Foxp3+ cells present in human lymph nodes, tonsils, spleens, and intestines did not express EBI3. Consistent with these in situ observations, Treg cells purified from blood or tonsils were negative for EBI3 by immunoblotting. Other human T cell subsets, including effector T cells, naive and memory CD4+ T cells, CD8+ and γδ T cells also did not constitutively express EBI3, which contrasts with IL-35 expression observed in murine CD8+ and γδ T cells. Furthermore, although CD3/CD28 stimulation consistently induced low levels of EBI3 in various CD4+ T cell subsets, no EBI3 could be detected in CD3/CD28-stimulated Treg cells. RT-PCR analysis showed that, whereas p35 transcripts were detected in both Teff and Treg cells, EBI3 transcripts were detected only in activated Teff cells, but not in resting or activated Treg cells. Thus, in contrast to their murine counterpart, human Treg cells do not express detectable amounts of IL-35.

Human rhinoviruses induce IL‐35‐producing Treg via induction of B7‐H1 (CD274) and sialoadhesin (CD169) on DC

“…4B). This is in accordance to previous findings, which show that p35 is constitutively expressed in various types of human T cells [6]. T cells previously activated with R-DC additionally stimulated with PMA/Ionomycin showed a slight increase in p35 and EBI3 (Supporting Information …”

“…1 Treg do not constitutively express IL-35 and induction of FOXP3 upregulates neither EBI3 nor p35 mRNA in human T cells [6,7]. Yet, recombinant mouse IL-35 was shown to inhibit the proliferation of mouse effector T cells in vitro.…”

FOXP3+ regulatory T cells and their functional regulation

“…44,45 IL-35 is another inhibitory cytokine that can be produced by Treg in mice, 46 where IL-35 deficient Treg cells were found unable to control disease in an inflammatory bowel disease mouse model. 46,47 The suppressive function of Treg cells could also occurs through disruption of target cell metabolism. Treg cells highly express the IL-2 receptor a-chain on their cell surface, which facilitates high consumption of IL-2.…”

Interleukin (IL)-35 is raising our expectations

“…However, French scientists published their surprising discovery not long ago; they reported that although CD3/CD28 stimulation induced low levels of EBI3 in various human CD4 + T cell subsets, no EBI3 could be detected in CD3/ CD28-stimulated human Treg cells 66 ; furthermore, whereas p35 mRNA were detected in both Teff and Treg cells, EBI3 mRNA were detected only in activated human Teff cells, but not in resting or activated human Treg cells, which contrasted with their murine counterpart, indicating the unknown role of IL-35 in human T cells. Thus, the composition of IL-35 receptor, IL-35-related cell signaling pathway, the different expression patterns of IL-35 between human and murine T cells, as well as the molecular mechanisms hidden behind its more biological activities requires to be further investigated.…”