The clonal composition of human CD4+CD25+Foxp3+ cells determined by a comprehensive DNA-based multiplex PCR for TCRB gene rearrangements

The characterization of the T-cell receptor (TCR) repertoire of CD4+ regulatory T cells (TR) has been limited due to the RNA degradation that results following permeabilization and fixation as routinely used for intracellular staining of Foxp3. In the present study the clonal composition of human umbilical cord blood (UCB) and adult peripheral blood mononuclear cell (PBMC) CD4+ TR and non-TR was characterized by a DNA-based multiplex PCR which allowed for the consistent clonotypic characterization of cells that have undergone fixation and permeabilization. To validate this method, CD8+ T cells from two HLA A⁎0201 individuals were sorted and compared clonotypically based upon their ability either to secrete interferon-γ in response to a CMV pp65 epitope or to bind to the corresponding pMHC I tetramer. Clonotypes shared between the CD4+CD25+Foxp3+ and CD4+CD25+Foxp3− subsets were observed in all 3 UCB and in one adult PBMCs, suggesting that naïve and memory CD4+ TR can share the same clonotypes as CD4+ non-TR in humans.