Abstract: The present invention discloses new, specific uses of polypeptides denominated as suppressive macrophage activation factors (SMAF's). More specifically, the present invention discloses that SMAF-1 and/or SMAF-2 modulate the production of Th1, Th2 and/or Th3 cytokines and indicates how the latter molecules, nucleic acids encoding them and antibodies against them can be used to treat diseases mediated by type 1, type 2 and/or type 3 responses such as inflammation, infections, allergies, autoimmune diseases, transplant rejections, graft-versus-host disease, malignancies and diseases involving mucosal immunity.