Hi there, Cellcept might help with some of the inflammation in the arteries, but you should be a blood thinner if you have protein S disorder. Protein S is a disease where you are more prone to forming blood clots, and doesn t necessarily cause narrow arteries. I disagree with your doctor, and I would recommend being on a blood thinner such as warfarin or xarelto, as protein S deficiency can lead to deep vein thrombosis or even pulmonary embolism, which can be fatal. I d recommend seeing a hematologist for your protein S disorder, and have them evaluate you for an autoimmune disease affecting your arteries. If you only have protein S deficiency, then cellcept may not be necessary and may actually not be helping you. I hope this answers your questions. Please feel free to contact me should you have any further questions.