Human CD4+ CD25+ Foxp3+ regulatory T cells do not constitutively express IL-35

Area of Science:

• Immunology
• Cell Biology

Background:

• Interleukin-35 (IL-35) is a heterodimeric cytokine implicated in immune suppression.
• In mice, IL-35 is constitutively expressed by regulatory T cells (Treg cells) and contributes to their function.
• The expression and role of IL-35 in human Treg cells remain largely uncharacterized.

Purpose of the Study:

• To investigate the expression of IL-35 in human Treg cells.
• To compare IL-35 expression in human Treg cells with other human T cell subsets and murine Treg cells.

Main Methods:

• Double-staining immunofluorescence analysis of human tissues (thymus, lymph nodes, tonsils, spleen, intestines).
• Immunoblotting of purified human Treg cells from blood and tonsils.
• RT-PCR analysis of EBI3 and p35 transcripts in human T cell subsets.
• Analysis of T cell subsets including CD4(+)CD25(+)Foxp3(+) Treg cells, effector T cells, naive/memory CD4(+) T cells, CD8(+) T cells, and gammadelta T cells.

Main Results:

• Human Treg cells (Foxp3(+) or CD25(+)) did not coexpress EBI3 in various tissues.
• Purified human Treg cells showed no detectable EBI3 protein.
• While p35 transcripts were found in both effector and Treg cells, EBI3 transcripts were absent in resting and activated Treg cells.
• CD3/CD28 stimulation induced low EBI3 levels in some T cell subsets but not in Treg cells.
• Human T cell subsets, unlike murine counterparts, did not constitutively express EBI3.

Conclusions:

• Human Treg cells do not express detectable levels of IL-35.
• This finding contrasts with the established expression of IL-35 by murine Treg cells.
• The absence of IL-35 in human Treg cells suggests potential differences in immune regulation mechanisms between humans and mice.