CD26: a negative selection marker for human Treg cells

Area of Science:

• Immunology
• Cell Biology

Background:

• Regulatory T (Treg) cells are crucial for immune homeostasis, but their therapeutic use is limited by difficulties in accurate identification and isolation.
• Current methods relying on markers like CD25 and CD127 are often non-specific, as these are also expressed on activated effector T (Teff) cells.

Purpose of the Study:

• To investigate the expression of CD26, an extracellular peptidase, as a potential marker for distinguishing Treg cells from Teff cells.
• To evaluate the utility of CD26 in combination with existing markers for improved Treg cell isolation and quantification.

Main Methods:

• Flow cytometry analysis was performed to assess CD26 expression levels on human T cell subsets.
• CD26 expression was compared between Treg cells (defined as CD4+CD25high or CD4+FoxP3high) and Teff cells (defined as CD4+CD25- or CD4+FoxP3-/low).
• Changes in CD26 expression upon T cell receptor (TCR) triggering were analyzed.

Main Results:

• Teff lymphocytes (CD4+CD25- or CD4+FoxP3-/low) exhibited high CD26 expression (CD26+).
• Treg cells (CD4+CD25high or CD4+FoxP3high) showed negative or low CD26 expression (CD26-/low).
• Upon activation, Teff cells significantly upregulated CD26, while Treg cells showed only a slight increase, maintaining distinct expression profiles.

Conclusions:

• CD26 serves as a reliable extracellular marker that differentiates Treg cells from Teff cells, even upon activation.
• Combining CD26 assessment with markers like CD25, FoxP3, or CD127 can enhance the accuracy of Treg cell quantification and isolation.
• This finding holds potential for improving therapeutic strategies involving Treg cells, particularly in autoimmune and inflammatory diseases.