title: Dynamics and Diagnostic Relevance of Kynurenine Serum Level after Kidney Transplantation.
abstract: BACKGROUND
  Inflammatory events after kidney transplantation (Tx) may lead to activation of the tryptophane-catabolizing enzyme indoleamine 2,3-dioxygenase followed by the formation of kynurenine (KYN). Post-transplant KYN serum levels in kidney allograft recipients were analyzed for their diagnostic value.
  
  
  METHODS
  This was a retrospective analysis of KYN levels (normal value: 2.7±0.6 nmol/ml) measured in 4083 blood samples collected from 355 kidney graft recipients in connection with uncomplicated courses, acute rejections (ARs), infections, and type of immunosuppression. We performed descriptive data analysis and analysis of variance.
  
  
  RESULTS
  In 212 recipients with immediately functioning grafts, the KYN levels dropped from pre-Tx 13.3±5.9 nmol/ml to nearly normal values at day 5 (5.8±3.0 nmol/ml). In patients with delayed graft function, the KYN reduction started only after the last hemodialysis treatment. With respect to ARs in recipients with creatinine values <300 µmol/l pre-AR, the increase of KYN levels depended on the severity of ARs (steroid-sensitive ARs: from 4.5±1.4 to 6.0±6.1 nmol/ml; steroid-resistant ARs: from 6.1±3.1 to 12.9±7.1 nmol/ml; vascular rejections: from 5.8±3.0 to 16.9±9.1 nmol/ml). In patients with creatinine values ≥300 µmol/l pre-AR, a further increase of the KYN level (from 10.1 to 13.2 nmol/ml) was only observed in severe, steroid-resistant ARs. With respect to infections evaluated, the KYN levels before diagnosis/start of treatment were 5.7±3.4 nmol/ml in asymptomatic CMV infections, 7.5±4.4 nmol/ml in CMV diseases, 8.3±3.3 nmol/ml in pneumonia, and 10.4±6.5 nmol/ml in bacterial sepsis.
  
  
  CONCLUSIONS
  Serum KYN seems to be a reliable diagnostic tool for the assessment of post-transplant inflammatory complications, already in an early stage, and for monitoring the efficacy of therapeutic interventions. Prospective studies are recommended.
authors.affiliation: Renal Transplant Centre, formerly Municipal Friedrichshain Hospital, Berlin, Germany.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Kaden
authors.affiliation: University of Ulm, Centre of Surgery, Ulm, Germany.
authors.forename: Dietmar
authors.initials: D
authors.lastname: Abendroth
authors.affiliation: Psy Consult Scientific Services, Frankfurt am Main, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Völp
authors.affiliation: University of Ulm, Centre of Surgery, Ulm, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Marzinzig
mesh_terms: D000328:Adult; D005260:Female; D006084:Graft Rejection / Q000097:blood / Q000175:diagnosis* / Q000517:prevention & control; D006801:Humans; D007166:Immunosuppressive Agents / Q000627:therapeutic use; D016030:Kidney Transplantation / Q000379:methods*; D007737:Kynurenine / Q000097:blood*; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011379:Prognosis; D012189:Retrospective Studies; D016896:Treatment Outcome
chemical_list: D007166:Immunosuppressive Agents; D007737:Kynurenine