When to Escalate
Immunosuppression Protects the Graft—but Narrows the Safety Margin
A transplanted organ can be recognized as foreign by the recipient’s immune system.
A transplanted organ can be recognized as foreign by the recipient’s immune system. Activated T lymphocytes may then injure the graft, while inadequate medication exposure allows rejection to progress. Immunosuppressants interrupt this response, but the same reduction in immune activity increases susceptibility to infection and malignancy and can blunt the usual signs of illness. Canadian transplant centres commonly use tacrolimus, mycophenolate mofetil, and a corticosteroid as first-line maintenance therapy after kidney, liver, and heart transplantation. These drugs are used together because they suppress different parts of the immune response; they are not interchangeable, and they are not taken only when rejection symptoms appear. Tacrolimus blocks calcineurin. This prevents transcription of interleukin-2 and reduces T-cell activation. Mycophenolate mofetil inhibits inosine-5′-monophosphate dehydrogenase, reducing the guanosine nucleotides needed for lymphocyte proliferation. Corticosteroids provide broader anti-inflammatory and immunosuppressive effects. The clinical balance is narrow: too little exposure risks graft injury, while too much exposure can produce nephrotoxicity, neurotoxicity, metabolic complications, cytopenias, or serious infection. That is why a dose is interpreted with the patient’s symptoms, laboratory trends, timing of the blood sample, and medication...