Provided are methods of administering peptides containing portions of or corresponding to an agent to be administered, such as a cell or molecule expressed by such cell such as a recombinant protein such as a chimeric receptor. In some embodiments, the administration is in conjunction with treatment methods employing the agent, e.g., cell or chimeric receptor, such as adoptive cell therapy methods. The chimeric receptor can be a chimeric antigen receptor (CAR). The peptides contain an epitope of the recombinant receptor and, in some embodiments, are capable of downregulating or reducing immune responses against the chimeric receptor, such as CAR. Also provided are such peptides and compositions that can induce tolerance to an agent such as a chimeric receptor, such as a CAR.
