Objective To evaluate the applied value of functional immunity measured by the ImmunKnow assay in the diagnosis of post-transplant infection in Chinese 1iver recipients.Methods Thirty-eight normal adults and 68 adult liver transplant recipients were under investigation.Whole blood samples from either normal volunteers(each sample for one person)or the liver recipients(one or more samples for one person)were collected freshly and cultured within 6h.The CD4+T cells were selected and their ATP value was assayed the next day.The liver recipients were grouped in stable status(n=52)or infection(n=64)according tO their clinieal manifestation.Results The average ATP value in the recipients with infection after liver transplantation was 165.7±100 μg/L,significantly lower(P＜0.05)than that in stable recipients(309±126 μg/L)or normal volunteers (292±83 μg/L).The low ATP levels in post-transplant recipients had fair good correlation to infection clinically(RR=0.5021,P＜0.01).Infectious risk was high when ATP value was less than 165μg/L(OR=11,95%CI 3.9-32.2,P＜0.01).Specificity and sensitivity of low ATP value in post-transplant infection were 86.53%and 73.81% respectively,Conclusion ImmuKnow assay provides a new tool in monitoring immune status in post-transplant recipients,and call helpfully predict and diagnose clinical infection.