Abstract： Objective To assess the clinical application of Cylex ImmuKnow assay in patients with renal dysfunction after liver transplantation for individualized immunosuppressive therapy.Method Twenty adult patients undergoing liver transplant between January 2009 and December 2011 received regular ImmuKnow assay monitoring combined with determination of serum tacrolimus trough concentration to guide immunosuppressive regimens,all of whom showed sustained renal dysfunction 6 months after transplant with normal and stable liver function.Clinical data were collected to observe the changes of renal function in those patients after treatment.Results The recipients were followedup for 15-54 months,received ImmuKnow assay 61 times and the results fluctuated 33-943 μg/L [median 282 μg/L,interquartile range (IQR) 267 μg/L].After ImmuKnow monitoring,serum creatinine level in patients was decreased significantly from median 151.8 μmol/L with IQR 44.9 μmol/L to median 114.9 μmol/L with IQR 35.3 μmol/L (Z =-3.845,P =0.000),and estimated glomerular filtration rate (eGFR) was increased significantly from median 0.746 mL/s with IQR 0.025 mL/s to median 1.005 mL/s with IQR 0.454 mL/s (Z =-3.771,P =0.000).ImmuKnow results showed a linear correlation with the white blood cell count in patients (Spearman correlation coefficient r =0.429,P =0.001),but no linear correlation with the patients' age,primary disease before transplantation,postoperative time,serum tacrolimus trough concentration,lymphocyte count,CD3+ T lymphocyte count,CD4+ T lymphocyte count or CD4+/CD8+ T lymphocyte ratio (P＞ 0.05).Conclusion Cylex IrmmuKnow assay can be applied in patients with renal dysfunction after liver transplantation for individualized immunosuppressive therapy monitoring,which is of certain clinical value.