As queries by some very intelligent readers have come in, I would like to explain further the points that I may have missed on earlier. when I mentioned biomarkers I meant for example in kidney transplantation, after the procedure when on long term immunosuppression there is kidney injury (either due to drug nephrotoxicity or chronic rejection caused by insufficient immunosuppression)the current marker used in clinic fail to detect it until aproximately more than 50% damage to the organ is done much of which can be irreversible. If we catch the injury early on as its happening we can modulate immunosuppressant dosage accordingly. we can increase the dose if there is less immunosuppression causing chronic rejection and decrease the dosage if there is immunosuppression drug toxicity. Unfortunately in clinic right now, first the detection is late second due to similar injury manifestation by both chronic rejection and drug nephrotoxicity, there isn't yet a measure to find out which one of them is causing the injury, where detection means totally different preventive measure as I mentioned earlier. So to find biomarkers that can detect organ injury early on post transplantation is one of the things that can change the graft and patient survival rates. An ideal biomarker should be non-invasive (lets say from urine / blood. Invasive would be a tissue biopsy), it should be inherently involved in the biochemical pathways that result in the disease symptom so that if there is a slight change in the state of the disease we are readily able to detect it via change in concentration/state of this biomarker. Considering kidney transplanation, some biomolecule in urine will be an ideal candidate because it will be intimately associated with the kidney (because organ in question produces the biomarker directly). Today creatinine in blood and urine (along with tissue biopsy and histology to see damage)is used as a gold standard in transplantation related kidney injury, but even for kidney injury it has shown be quite insensitive. Addressing local immunosuppression, yes it seems almost sci-fi to think about something like that given the complexity and exposure to everything in the body, but it may not be as far fetched. Though I have very limited knowledge about this but I have heard of some very interesting theories people are working on but it may be too preliminary to mention it here. our best bet is still a system-wide efficient and non toxic immunosuppression along with very sensitive biomarkers to detect any adverse effects. The success of a transplant is based on tons of factors because anything in body is everything and anything is connected to everything. for example if there is a liver transplant and popular immunosuppressants are in effect then there are very high chances there will be kidney specific injury. if kidney is injured it wont be able to do its various jobs (filtering, BP etc.) and we will have system wide effects where it will be hard to pinpoint what caused it. While there maybe no such thing as ideal immunosuppression (because we are doing something that nature did not intend upon happening) with very diligent patient monitoring with current day immunosuppressants (please don't quote me on this), in cases people have lived with their kidney grafts for as long as 20-25 years. Majority of kidney transplants see anywhere from 10-14 years until they need a retransplant.
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You make super points. The father of a former student had a lung transplant, and would frequently get into trouble; and it was a nightmare to try to figure out what was going on each time. Think: He has, let's say, dyspnoea. Why? It could be an infection; but the biomarker (raised white blood count) would be blunted by immunosuppression. Or: He could be rejecting the transplant. Or: He could be having toxicity from his immunosuppressives. Though sometimes lifesaving, having a major organ transplant is no picnic.
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