Immunodiagnostics: evaluation of functional T-cell immunocompetence in whole blood independent of circulating cell numbers.

The need for a systematic approach for immune function monitoring has becoming increasingly apparent in the past decade due to the rapid expansion of the development and use of immunomodulatory drug therapies and vaccines. While there has been a great deal of progress in the development of methodologies for evaluating and enumerating T-lymphocyte responses to infection and cancer, the translation of these assays into the clinical setting has remained seemingly elusive. This is likely due to inherent difficulties in the standardization and validation of cell-based assays. Here, we describe a novel assay that measures ATP production in CD4(+) T-lymphocytes in response to stimulation. Results from the test, unlike absolute cell counts, assess the functional response of lymphocytes. Clinical utility of the assay has been demonstrated in managing immunosuppression in solid organ transplant recipients such that adverse events such as infection and rejection can be avoided. The need for a global immune response test in the clinical setting of transplantation and the value of such a test in post-transplant management is discussed. Furthermore, additional applications of this assay for monitoring diseases that impact immune function including autoimmunity and infection are considered.

Assessing relative risks of infection and rejection: a meta-analysis using an immune function assay.

BACKGROUND: Long-term use of immunosuppressants is associated with significant morbidity and mortality in transplant recipients. A simple whole blood assay that has U.S. Food and Drug Administration clearance directly assesses the net state of immune function of allograft recipients for better individualization of therapy. A meta-analysis of 504 solid organ transplant recipients (heart, kidney, kidney-pancreas, liver and small bowel) from 10 U.S. centers was performed using the Cylex ImmuKnow assay. METHODS: Blood samples were taken from recipients at various times posttransplant and compared with clinical course (stable, rejection, infection). In this analysis, 39 biopsy-proven cellular rejections and 66 diagnosed infections occurred. Odds ratios of infection or rejection were calculated based on measured immune response values. RESULTS: A recipient with an immune response value of 25 ng/ml adenosine triphosphate (ATP) was 12 times (95% confidence of 4 to 36) more likely to develop an infection than a recipient with a stronger immune response. Similarly, a recipient with an immune response of 700 ng/ml ATP was 30 times (95% confidence of 8 to 112) more likely to develop a cellular rejection than a recipient with a lower immune response value. Of note is the intersection of odds ratio curves for infection and rejection in the moderate immune response zone (280 ng/ml ATP). This intersection of risk curves provides an immunological target of immune function for solid organ recipients. CONCLUSION: These data show that the Cylex ImmuKnow assay has a high negative predictive value and provides a target immunological response zone for minimizing risk and managing patients to stability.

Monitoring immune function during tacrolimus tapering in small bowel transplant recipients.

Long term use of immunosuppressants impacts the cardiovascular system and increases the risk of infection and malignancy. To effectively reduce immunosuppression in a transplant recipient a tool is needed to directly monitor the level of immune function. The Cylex(R) Immune Cell Function Assay, approved by the FDA for the assessment of cell-mediated immunity, shows promise as an objective measure of a transplant recipient's immune function. In a blinded retrospective study, the immune function was compared to clinical courses and histological examinations of biopsies of 20 small bowel transplant recipients during periods of immunosuppressant tapering. Eight patients with no major adverse events or changes of immunosuppressive therapy had moderate to low immune function and were categorized as immunologically and clinically stable. Twelve patients displaying strong immune responses were immunologically and clinically volatile requiring addition of steroids and or OKT3. Results validate the clinical utility of the Cylex Immune Cell Function Assay as an objective tool for assessing immune function. By evaluating immune function, physicians now can identify those patients who are candidates for minimization of immunosuppressant therapy, manage the timing and rate of immunosuppressant weaning and be forewarned of increased patient risk.

Immune cell function testing: an adjunct to therapeutic drug monitoring in transplant patient management.

Each year, 55 000 organ transplants are performed worldwide. Cumulatively, the number of living organ recipients is now estimated to be over 300 000. Most of these transplant recipients will remain on immunosuppressive drugs for the remainder of their lives to prevent rejection episodes. Controlled doses of these drugs are required to prevent over-medication, which may leave the patient susceptible to opportunistic infection and drug toxicity effects, or under-dosing, which may lead to shortened graft survival because of rejection episodes. This paper describes the result of a multicenter study conducted at the Universities of Pittsburgh, Alabama and Maryland to evaluate an in vitro assay (CylexTM Immune Cell Function Assay) for the measurement of global immune response in transplant patients receiving immunosuppressive therapy. The assay uses a whole blood sample to maintain the presence of the drug during incubation. Following overnight incubation of blood with phytohemagglutinin (PHA), CD4 cells are selected using paramagnetic particles coated with a monoclonal antibody to the CD4 epitope. The CD4-positive cells are targeted as major immunosuppressive drugs are designed to specifically inhibit T-cell activation which has been implicated in rejection. The data generated at these three sites were submitted in support of an Food and Drug Association (FDA) application for the use of this assay in the detection of cell-mediated immunity in an immunosuppressed population. The assay was cleared by the FDA on April 2, 2002. This cross-sectional study was designed to establish ranges for reactivity of this bioassay in the assessment of functional immunity for an individual solid organ recipient at any point in time.