A method is provided for treating or preventing an undesired immune response in a patient, comprising: administering to said patient, cells that transiently express, and/or that are transfected with mRNA encoding, one or more polypeptides selected from the group consisting of an IL-4 receptor agonist, an IFN-gamma receptor antagonist, an IFN-alpha receptor antagonist, an IL-12 receptor antagonist, an IL-23 receptor antagonist, and a TNF antagonist. Preferably, the cells selectively accumulate in one or more secondary lymphoid tissues at or proximate to the site of the undesired immune response. Related compositions are provided. The methods and compositions are useful for the treatment or prevention of undesired immune responses including, but not limited to, transplant rejection, autoimmune disease, allergy and immune responses directed against therapeutic compositions.