Human T cells express CD25 and Foxp3 upon activation and exhibit effector/memory phenotypes without any...

Area of Science:

• Immunology
• Cell Biology

Background:

• The role of Foxp3 as a marker for human regulatory T cells (Tregs) is debated, with conflicting reports on its association with regulatory function.
• Some studies suggest human Foxp3+ T cells lack regulatory capacity, while others indicate a role in inhibiting T cell proliferation.

Purpose of the Study:

• To investigate the expression and functional implications of Foxp3 in human T cells upon activation.
• To clarify whether Foxp3 expression in human T cells correlates with regulatory function.

Main Methods:

• Human T cells were activated using various methods, including phorbol 12-myristate 13-acetate/ionomycin, mixed lymphocyte reaction, and CD3/CD28 stimulation.
• T cell proliferation was assessed using BrdU and CFSE staining.
• Flow cytometry was employed to analyze Foxp3 expression, cell proliferation, viability, and T cell phenotypes.

Main Results:

• Both CD4+ and CD8+ T cells expressed Foxp3 following in vitro activation.
• Foxp3 expression was more stable in CD4+CD25+ T cells than in CD8+CD25+ T cells.
• Activated CD4+CD25+Foxp3+ T cells exhibited effector and memory phenotypes (CD44+, CD62L+). Both Foxp3- responder T cells and CD4+Foxp3+ T cells proliferated upon CD3/CD28 activation.

Conclusions:

• Foxp3 expression in human CD4+CD25+ T cells does not inherently signify regulatory function.
• Upregulation of Foxp3 on effector (CD44+) and memory (CD44+CD62L+) T cells post-stimulation suggests activation-induced regulation of Foxp3 expression.