The invention provides a method of detecting acute renal allograft rejection in a subject as well as a method of stratifying a subject received a renal allograft and undergoing immunosuppressive therapy for alteration of the therapy. These methods comprise administering to the subject a probe capable of specifically binding to T lymphocytes, the probe being detectable by ultrasound. An allotransplanted kidney of the subject is exposed to ultrasound. The level of T lymphocytes in the kidney is detected. An elevated level of T lymphocytes in the kidney indicates an increased risk of renal allograft rejection and/or that the subject is in need of an alteration of the immunosuppressive therapy.
