As long as those who are immunosuppressed take appropriate precautions, they should be okay. Some of my colleagues have been diagnosed with various autoimmune and inflammatory conditions, are on immunosuppressants, and are still very productive in clinical practice. Yes, should they get sick, any infections they get are more severe, and yes, they are much more mindful of any symptoms they may have. Whether that is worth the risk depends on each individual. For anyone in this situation, speak to your doctor to see how high this risk may be, as immunosuppression is not a binary variable.
Once accepted, they should let their school know that they are immunosuppressed, and the school will alert the relevant preceptors and attendings to avoid putting them in situations that may be harmful to their health. On the teaching services, I'm regularly informed by the clerkship and residency directors of any medical issues that I should be mindful of, and is strictly on a need to know basis (eg "they need to leave by this time on Thursdays each week", etc). This information is handled confidentially, and is not held against the student.
Also note that not all specialties will require patient contact, eg diagnostic radiology.
Disclaimer: none of this is medical advice. For medical advice, consult with your doctors.
