Signatures of human regulatory T cells: an encounter with old friends and new players

BACKGROUND: Naturally occurring CD4(+)CD25(+ )regulatory T cells (T(Reg)) are involved in the control of autoimmune diseases, transplantation tolerance, and anti-tumor immunity. Thus far, genomic studies on T(Reg )cells were restricted to murine systems, and requirements for their development, maintenance, and mode of action in humans are poorly defined. RESULTS: To improve characterization of human T(Reg )cells, we compiled a unique microarray consisting of 350 T(Reg )cell associated genes (Human T(Reg )Chip) based on whole genome transcription data from human and mouse T(Reg )cells. T(Reg )cell specific gene signatures were created from 11 individual healthy donors. Statistical analysis identified 62 genes differentially expressed in T(Reg )cells, emphasizing some cross-species differences between mice and humans. Among them, several 'old friends' (including FOXP3, CTLA4, and CCR7) that are known to be involved in T(Reg )cell function were recovered. Strikingly, the vast majority of genes identified had not previously been associated with human T(Reg )cells (including LGALS3, TIAF1, and TRAF1). Most of these 'new players' however, have been described in the pathogenesis of autoimmunity. Real-time RT-PCR of selected genes validated our microarray results. Pathway analysis was applied to extract signaling modules underlying human T(Reg )cell function. CONCLUSION: The comprehensive set of genes reported here provides a defined starting point to unravel the unique characteristics of human T(Reg )cells. The Human T(Reg )Chip constructed and validated here is available to the scientific community and is a useful tool with which to study the molecular mechanisms that orchestrate T(Reg )cells under physiologic and diseased conditions.