The present invention relates to the use of one inhibitor or of several inhibitors of alanyl aminopeptidases and/or of enzymes having a similar substrate specificity for the induction of the production of TGF-beta1 and of the expression of TGF-beta1 in and/or on Treg cells and relates to the use for preventing and/or treating autoimmune diseases, allergies, arteriosclerosis and for suppressing graft rejection reactions. The invention furthermore relates to uses, wherein peptide fragments of pathogenic autoantigens or synthetic analogs and/or specific antigenic components of pathogenic microorganisms are used in addition.