Diagnostic value of regulatory T cells: a new facet of a much studied cell population.

FOXP3 has emerged as the most suitable marker for Treg and has been studied in both experimental and clinical transplantation. Biopsy samples have been stained for FOXP3+ cells whereas FOXP3 messenger RNA levels have been measured in blood and urine samples after transplantation. Although not unanimous, some studies have suggested that FOXP3 is associated with better outcome and can also serve as a marker of rejection. Routine staining of FOXP3+ cells in biopsy samples and FOXP3 messenger RNA levels in urine of kidney transplant patients may determine each patient's immunological profile, enabling less immunosuppression to be given to those at lower risk.