This is a prospective, tissue-based, low-risk, non-pharmacological study that will include adult patients undergoing solid organ transplantation (heart, liver, lung, kidney) followed at the following Units of the IRCCS Azienda Ospedaliero-Universitaria di Bologna (IRCCS AOUBO):
* Heart Failure and Transplants (heart-lung) * Internal Medicine for the Treatment of Severe Organ Failures (liver) * Nephrology, Dialysis, and Transplantation (kidney).
Adult patients (≥ 18 years old at the time of enrollment) who have undergone at least one of the following: Liver transplant, Kidney transplant, Heart transplant, Lung transplant during the study period.
Informed consent acquisition.
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