Methods and compositions for noninvasive detection of organ transplant rejection

A method of detecting a T cell cytotoxicity driven immune condition and/or the likelihood thereof in a subject, the method comprising:

• i) administering a nanosensor to the subject, said nanosensor comprising:
• a) a scaffold;
• b) a peptide substrate coupled to the scaffold, wherein the peptide substrate is capable of being cleaved by Granzyme B;
• and
• c) a detectable reporter coupled to the scaffold by the peptide substrate, wherein in vivo cleavage of said peptide substrate releases said detectable reporter from the scaffold;
• ii) detecting a level of said detectable reporter in a blood or urine sample collected from the subject;
• wherein the presence of detectable reporter indicates the subject has or is likely to have a T cell cytotoxicity driven immune condition;
• and
• iii) treating the subject for a T cell cytotoxicity driven immune condition when the detectable reporter is detected.