Unless the transplant comes from your own pancreas (islet cell transplant for chronic pancreatitis) the transplant will come from donor material. This means that your body will mount an immune rejection attack on the donor tissue requiring lifelong immunosuppressant medication to be taken. This process which is so necessary for the success of the transplant exposes the patient to a number of well established opportunistic infections which may have to be countered by very specific antibiotics, antivirals and anti-fungals.
In some cases the emergence of specific tumour types have also been known to be with long-term immunosuppressive therapy. This is another reason to carefully assess the risk-benefit ratio of current treatment versus transplantation