Molecular characterization of human regulatory T cells in health and disease

Abstract

Naturally occurring CD4+CD25+ regulatory T cells (TReg) play a pivotal role in the maintenance of peripheral tolerance. TReg are involved in the control of autoimmunity, transplantation tolerance and anti-tumor responses. Thus far, genomic studies on TReg were restricted to murine systems, and requirements for their development, maintenance, and mode of action in humans remain poorly defined. To improve molecular characterization of human TReg, a unique customized microarray was compiled, consisting of 350 TReg associated genes. Following validation of the Human TReg Chip, TReg specific gene expression signatures were created from 11 individual healthy donors. Statistical analysis identified 62 genes differentially expressed in TReg versus naive T cells. Among them, several “old friends” (e.g. FOXP3, CTLA4, CCR7) that are known to participate in TReg function were recovered. Strikingly, the vast majority of genes has not previously been associated with TReg at all (such as LGALS3, TIAF1, TRAF1). Most of these “new players” however, have been described in the pathogenesis of autoimmunity and cancer. Real-time RT-PCR of selected transcripts validated the microarray results, while FACS analysis confirmed correlation of gene and protein expression. Activation experiments revealed LGALS3 and TNFRSF1B as new putative human TReg markers. Pathway analysis was applied to extract signaling modules underlying human TReg function. Using the comprehensive set of unravelled genes from healthy donors as a reference, gene expression of TReg was studied in patients suffering from renal cell carcinoma (RCC) or inflammatory bowel disease (IBD). As examples for tumor and autoimmune diseases, respectively, complementary dysregulation in the TReg compartment was expected. Apart from numerical aberrations, altered gene expression in patient-derived TReg could be revealed, contributing to functional deficits and thus to disease pathogenesis.