Purpose: To identify the levels of functional immunity measured by the ImmuKnow assay in Chinese liver transplantation recipients and its application in monitoring the risk of posttransplant infection.

Methods: Forty-five apparent healthy Chinese and 106 adult liver transplant (LT) recipients were under investigation. LTs were grouped in stable status or infection according to their clinical diagnosis. Whole blood samples were collected freshly and cultured within 6 hr, the CD4(+) T cells were selected, and their adenosine triphosphate (ATP) value was assayed the next day. Before stimulation, we also examined the percentage of T-helper (Th; CD3(+) CD4(+)) and T-suppress (Ts; CD3(+) CD8(+)) lymphocyte subpopulations and the ratio of Th/Ts.

Results: The average ImmuKnow assay in infectious LT recipients was 128 + or - 84 ng/mL, significantly lower (P<0.05) than that in stable LTs (305 + or - 149 ng/mL) or in normal adults (301+ or - 101 ng/mL). The ImmuKnow values in LTs had a good negative correlation to infection clinically (r = -0.6217, P<0.001). Infectious risk was high when the ImmuKnow value was less than 130 ng/mL (odds ratio=13, 95% confidence interval 6.0-29.4, P<0.01). The sensitivity of low ImmuKnow values in posttransplant infection was 85.2%, significantly higher than those of Th/Ts ratio and immunosuppressant trough levels (P<0.01); specificity was 76.3%, comparable with that of Th/Ts ratio (75.5%), but greatly higher than immunosuppressant trough levels (P<0.01). ImmuKnow ATP values had no correlation with Th/Ts ratio or immunosuppressant trough levels.

Conclusion: ImmuKnow ATP levels are lower in LT recipients with infection, which provides a new tool in monitoring posttransplant infection, and an index of tailoring immunosuppression clinically.