The present invention relates to a bifunctional agent that is suitable for suppressing the activation of T lymphocytes, said agent comprising polypeptides that are capable of activating the T cell receptor (TCR) and a transforming growth factor beta receptor (TGFβR) of said T lymphocytes. The present invention further relates to a method for the suppression of the activation of T lymphocytes, comprising the step of simultaneously activating the TCR and a TGFβR in physical proximity at the surface of said lymphocytes.
