Evaluation of Immuknow assay for predicting the risk of infection and rejection in liver transplantation recipients in Hong Kong

Abstract

Background: Liver transplantation is a curative method for end-stage liver diseases, small unresectable hepatocellular carcinoma and acute liver failure. The discovery of immunosuppressive drugs increases the survival rate of liver transplanted recipients by reducing the incidence of graft rejection. Several complications such as renal dysfunction and increase risk of malignancy result from life-long treatment of transplanted recipients with immunosuppressant. If recipients are over-immunosuppressed, the risk of infection might be increased. On the other hands, if recipients are under-immunosuppressed, the risk of rejection would be increased. It should be useful if a test or a bio-marker that could predict and differentiate infection and rejection in transplanted recipients. Therefore, patients could be treated before adverse conditions. Although therapeutic drug monitoring has been performed as a routine test, it is mainly targeted for minimizing drug toxicity but little help in predicting infection and rejection. A new assay named Cylex? Immuknow? assay is designed to measure global cell mediated immunity of immunosuppressed population, by quantifying the amount of ATP synthesis by CD4+ T cells in response to PHA stimulation. It is undergoing evaluation in assessing the immune status of patients in order to predict the risk of infection and rejection, and also other conditions. (1, 2) Objectives: In this pilot study, we would like to evaluate ImmuKnow for predicting the risk of infection and rejection in liver transplanted recipients in Hong Kong. Methods: Blood samples were collected from liver transplanted recipients at different time intervals. The immune cell response of these patients was measured by Immuknow assay. Patients with low immune response might have a high risk of infection, patients with high immune response might have a high risk of rejection, and patients with moderate immune response should be clinically stable. Results and conclusion: Twenty-six blood samples were collected from eight transplanted recipients. The average Immuknow assay value for the post-transplant samples was 304.6 ng/mL ATP which represented moderate immune cell response according to the interpretation table. (Table 3) This was reasonable as the subjects were all clinically stable by well-controlled immunosuppression. The result was consistent with other studies. (1, 3) However, the association between low immune cell response and infection, and the association between high immune cell response and graft rejection could not be investigated as both of these conditions were not found in this pilot study. A larger study including episodes of infection and rejection should be conducted in order to evaluate the value of Immuknow assay more completely.