Abstract: The present invention uses the potency and efficacy of human glycoprotein-A repetitions predominant protein (GARP), the gene of which is located on chromosome 11q13-11q14 in the reprogramming of antigen-specific effector T-helper cells, which are CD4+, towards a regulatory pheno type of pre-determined suppressor activity. In contrast to the known regulatory protein Foxp3 that only induces an incomplete regulatory phenotype without suppressor function, GARP is more efficient in inducing suppressor activity. Further, the use of GARP in the manufacture of pharmaceutical compositions is provided, allowing the production of antigen-specific Treg-cells, having a predetermined suppressor activity for a specific antigen.