Human Peripheral Blood CD8+ CD28− T Cells of Renal Allograft Recipients Do Not Express FOXP3 Protein

IntroductionIn recent studies, the FOXP3 molecule has been suggested to be a marker of a suppressor subset of human CD8+ CD28− T cells based on correlations between the level of its mRNA and allograft function. Because this transcriptional factor produces a protein, we suggest that these correlations should focus on the FOXP3 protein. The aim of our study was to evaluate whether FOXP3 protein was present in cells of the CD8+ CD28− population in the peripheral blood of renal allograft recipients and whether the level of CD8+ CD28− FOXP3+ cells correlated with allograft function.MethodsThe study was performed on 30 renal allograft recipients with uneventful stable courses (n = 18) or biopsy-proven chronic rejection (n = 12). The immunosuppression was based on cyclosporine (n = 12) or rapamycin (n = 9). Peripheral blood mononuclear cells isolated from recipient blood samples were labeled with anti-CD8 and anti-CD28 MAbs conjugated with fluorochromes. After incubation, washing, and labeling using a PE anti-human FOXP3 Kit, we determined the percentage of cells by flow cytometry.ResultsFOXP3 protein expression was not observed either in the CD8+ CD28− population, or the whole populations of CD8+ or CD28− cells among patient groups.ConclusionsThe expression of FOXP3 protein in CD8+ CD28− cells seems to be of a questionable value as a diagnostic tool for allograft function, it is probably not a marker for the CD8+ CD28− T cell subset.