Paradoxically increased FOXP3+ T cells in IBD do not preferentially express the isoform of FOXP3 lacking exon 2

Area of Science:

• Immunology
• Gastroenterology

Background:

• Forkhead box P3 (FOXP3)+ regulatory T cells (Tregs) are crucial for gut inflammation control.
• Inflammatory bowel disease (IBD) shows a paradoxical increase in mucosal FOXP3+ T cells, some producing IL-17A.
• A FOXP3 splice variant (Δexon2) lacks inhibitory function, unlike full-length FOXP3.

Purpose of the Study:

• To test if IBD patients preferentially express the Δexon2 FOXP3 variant.
• To determine if increased mucosal Tregs in IBD are due to exclusive Δexon2 expression.

Main Methods:

• Used specific antibodies and primers to differentiate FOXP3 isoforms (full-length vs. Δexon2).
• Evaluated isoform expression in human intestinal tissue via immunohistochemistry and quantitative PCR.
• Analyzed cells using immunofluorescence microscopy and flow cytometry.

Main Results:

• No significant difference in Δexon2 relative to full-length FOXP3 expression was observed between IBD and control groups.
• Individual cells did not exclusively express the Δexon2 FOXP3 isoform in IBD or control tissues.
• FOXP3+ T cells from both IBD and control specimens could produce IL-17A in vitro but did not preferentially express Δexon2.

Conclusions:

• The study does not support the hypothesis that selective Δexon2 FOXP3 isoform expression explains Treg dysfunction in IBD.
• The findings suggest other mechanisms underlie the inability of FOXP3+ T cells to control inflammation and IL-17 production in IBD.