Use of an immune function assay to monitor immunosuppression

Development of an immune function assay by measuring intracellular adenosine triphosphate (iATP) levels in mitogen-stimulated CD4+ T lymphocytes

We developed an immune function assay for monitoring CD4+ T cells activity based on changes in intracellular adenosine triphosphate (iATP) levels after phytohemagglutinin (PHA) stimulation. Blood samples were obtained from 40 healthy subjects and 30 RTRs and incubated with 5 µg/mL of PHA for 15-18 hr at 37°C and 5% CO2. Afterward, the CD4+ T cells were separated by antibody-coated magnetic beads and lysed. Then, iATP content in unstimulated and stimulated conditions was measured by luciferin-luciferase reaction using a log-log standard curve. The iATP levels showed significant increase in CD4+ T cells in both healthy persons (mean: 550 ± 142 ng/mL vs. 109 ± 54 ng/mL) and RTRs (mean: 394 ± 160 ng/mL vs. 52 ± 37 ng/mL) after PHA stimulation (P < 0.001). However, the iATP production in RTRs was significantly lower than that in healthy individuals; both prior to and after stimulation with PHA (P < 0.001). No gender-specific difference in iATP production was observed between women and men subjects. This rapid and low-cost assay reflects the degree of immune cell function through assessment of CD4+ T cells activation. Thus, it can be used for evaluation of immune system status in immunodeficient individuals as well as in immunosuppressed transplant recipients who needs drug adjustment.

Evaluation of the immune function assay in pediatric living donor liver transplantation

The immune function (ImmuKnow) assay is a measure of cell-mediated immunity based on the peripheral CD4+ T cell ATP activity. The efficacy of ImmuKnow in pediatric LDLT is not well documented. The aim of this study was to assess the correlations between the ImmuKnow and the clinical status in pediatric LDLT recipients. A total of 716 blood samples were obtained from 60 pediatric LDLT recipients (one month to 16 yr of age). The recipient's status was classified as follows: stable, infection, or rejection. The ImmuKnow values in the pediatric LDLT recipients with a clinically stable status had a lower immune response (IQR 85-297 ATP ng/mL) than that previously reported in adults. Meanwhile, the ImmuKnow values of the stable patients were not correlated with age. Furthermore, a significant difference was found in the ImmuKnow values between the bacterial or fungal infection and stable groups, but not between the CMV or EBV infection and stable groups. The ImmuKnow levels in the pediatric LDLT were lower than those observed in the adult LDLT. The proposed reference value is between 85 and 297 ATP ng/mL in pediatric LDLT recipients. We conclude that the ImmuKnow assay could be helpful for monitoring pediatric LDLT recipients with bacterial or fungal infections.

Immune cell function assay does not identify biopsy-proven pediatric renal allograft rejection or infection

Management of pediatric renal transplant patients involves multifactorial monitoring modalities to ensure allograft survival and prevent opportunistic infection secondary to immunosuppression. An ICFA, which utilizes CD4 T-cell production of ATP to assess immune system status, has been used to monitor transplant recipients and predict susceptibility of patients to rejection or infection. However, the validity of this assay to reflect immune status remains unanswered. In a two-yr retrospective study that included 31 pediatric renal transplant recipients, 42 patient blood samples were analyzed for immune cell function levels, creatinine, WBC (white blood cell) count, immunosuppressive drug levels, and viremia, concurrent with renal biopsy. T-cell ATP production as assessed by ICFA levels did not correlate with allograft rejection or with the presence or absence of viremia. ICFA levels did not correlate with serum creatinine or immunosuppressive drug levels, but did correlate with WBC count. The ICFA is unreliable in its ability to reflect immune system status in pediatric renal transplantation. Further investigation is necessary to develop methods that will accurately predict susceptibility of pediatric renal transplant recipients to allograft rejection and infection.

Immune functional assay for immunosuppressive management in post-transplant malignancy

Immunosuppression management in post-transplant malignancy is challenging because of a lack of objective immunologic assessment tools. The ImmuKnow assay measures the ATP level from CD4 T cells, quantifying cell-mediated immunity and providing an insight into the immune status of transplant recipients. Its potential use in patients with post-transplant de novo malignancy was evaluated. Thirteen adult transplant patients with de novo malignancy were divided into survivors (n = 9) and non-survivors (n = 4) after malignancy treatment. Tacrolimus and the ImmuKnow levels were monitored before, during, and after malignancy treatment. The ImmuKnow level in non-survivors group was significantly lower before and after malignancy treatment compared to survivors group (p = 0.013 and 0.0014 respectively). In survivor group, the ImmuKnow level was significantly decreased during malignancy treatment (p = 0.019) but recovered to the initial level after the treatment. However, in non-survivor group, the ImmuKnow level remained suppressed throughout the observed period despite a reduction in immunosuppressive drug levels. The ImmuKnow assay can be an objective means evaluating immune status of patients with de novo malignancy. The ImmuKnow assay can express the degree of immune suppression induced by chemotherapeutic or radiation therapy and may be a useful tool in optimizing the timing of re-introduction of immunosuppression after malignancy treatment.

The impact of intercurrent EBV infection on ATP levels in CD4+ T cells of pediatric kidney transplant recipients

ImmuKnow measures ATP (ng/mL) in PHA-activated CD4+ T cells from patient's whole blood. According to published reports, median ImmuKnow is 258 ng/mL in stable pediatric kidney transplant (PKT) recipients > or =12 yr, and 165 ng/mL in those <12 yr. However, data on the effect of infection or AR on ImmuKnow are scarce. We studied the effect of Epstein-Barr virus (EBV) viremia on ImmuKnow in PKT with GD. Twenty-eight PKT with GD were reviewed. Group 1 has 19 PKT > or =12 yr, and group 2 has nine PKT <12 yr. Mean follow-up was 19.4 +/- 12 months. All ImmuKnow values discussed in this study were measured during GD +/- fever. None had ImmuKnow pretransplant. EBV DNA was isolated from patient blood by real-time PCR. Group 1 has eight boys and 11 girls (mean age = 16.6 +/- 2.4 yr). Group 2 has two boys and seven girls (mean age = 6 +/- 3.1 yr). Median ImmuKnow was 292 ng/mL in group 1, and 370 ng/mL in group 2. Nine children developed EBV viremia: two in group 1 (median ImmuKnow = 273 ng/mL), and seven in group 2 (median ImmuKnow = 475 ng/mL). Overall mean ImmuKnow in the nine EBV viremic patients was higher than that in the 19 non-viremic ones (422 +/- 176 ng/mL, and 302 +/- 113 ng/mL, respectively, unequal variance t-test, p = 0.08). Eight children developed AR (all in G1, median ImmuKnow = 272 ng/mL). In group 1, one patient developed concurrent EBV viremia and rejection, while another patient developed EBV viremia six months following a rejection episode. In group 2, none developed simultaneous AR, CMV, or BK virus infection with EBV viremia. None developed post-transplant lymphoproliferative disease. In summary, EBV viremia was paradoxically associated with high ImmuKnow in PKT <12 yr. This suggests strong co-stimulation of PHA-activated CD4+ T cells by EBV-transformed B cells.