The peptides of the invention comprise (i) a T-cell epitope of an antigen (self or non-self) with a potential to trigger an immune reaction presented by a class II major histocompatibility complex (MHC) determinant and recognized by a CD4+ T cell, more specifically, of an allergen or autoantigen, coupled, optionally, through the use of a linker to (ii) an amino acid sequence having a reducing activity, such as a thioreductase sequence. The peptides may be used for the prevention or treatment of immune disorders, more specifically, of allergic disorders or autoimmune diseases. The present invention thus provides methods of treatment or preventing immune disorders by using such peptides.