The present invention provides a method to quantitatively measure the response of a patient to an immune-modulator drug that will aid clinicians in the determination of the optimal combination/posology of immunosuppressant/immune-modulator drugs. In addition, this method will open the possibility for clinicians to make the necessary adjustments in immunosuppressive therapy, as a way to avoid organ rejection to actually take place. Furthermore, this method will significantly reduce side effects of immunosuppressant drugs, optimizing therapeutic scheme and dosages, enabling the determination of the most effective immunosuppression regimen at the lower dosages for each patient individually and monitoring of treatment efficiency along time, thus opening the door to treatment personalization.