Lymphocyte activation: changes in intracellular adenosine triphosphate and deoxyribonucleic acid synthesis

Evaluation of the Infection Risk in Dialysis and Chronic Kidney Disease Patients Using an ATP Monitoring Assay

The ATP monitoring assay is a useful biomarker for risk monitoring to detect infection and rejection episodes in transplant recipients. Hemodialysis patients have a higher rate of infectious mortality. Infections in hemodialysis patients are mainly caused by venous catheters, uremia, malnutrition and inflammation. However, the risk of infection episodes has not been evaluated using a lymphocyte ATP monitoring assay in hemodialysis and chronic kidney disease (CKD) patients. We measured the ATP amounts in the peripheral CD4+ cells of CKD (N = 85) and dialysis patients (N = 17) using an "Immuknow" assay kit. These CKD patients were divided, according to kidney disease stage, into G3a, G3b, G4, and G5 groups. The ATP amounts in CD4+ cells of the dialysis patients and each of the CKD groups were compared with healthy subjects. In both the dialysis and CKD patients, the ATP amounts in CD4+ cells were lower than in healthy subjects. Furthermore, there were significant differences in the ATP amounts between healthy subjects and each of the CKD-G3a, CKD-G3b, and CKD-G4 groups (P < 0.05). Patients with CKD-G3a, CKD-G3b and CKD-G4 were evaluated as being at high risk for infection according to the lymphocyte ATP monitoring assay. However, the ATP amounts in the dialysis and CKD-G5 patients did not differ from those in healthy subjects to a statistically significant extent. These results suggest that the ATP amount in the CD4+ cells of these patients with serve renal failure are influenced by dialysis treatment, uremia and/or oxidative stress.

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.

Update on in vitro cytotoxicity assays for drug development

BACKGROUND

in vitro cytotoxicity testing provides a crucial means of ranking compounds for consideration in drug discovery. The choice of using a particular viability or cytotoxicity assay technology may be influenced by specific research goals.

OBJECTIVE

Although the high-throughput screening (HTS) utility is typically dependent upon sensitivity and scalability, it is also impacted by signal robustness and resiliency to assay interferences. Further consideration should be given to data quality, ease-of-use, reagent stability, and matters of cost-effectiveness.

METHODS

Here we focus on three main classes of assays that are at present the most popular, useful, and practical for HTS drug discovery efforts. These methods measure: i) viability by metabolism reductase activities; ii) viability by bioluminescent ATP assays; or iii) cytotoxicity by enzymes 'released' into culture medium. Multi-parametric technologies are also briefly discussed.

RESULTS/CONCLUSION

Each of these methods has its relative merits and detractions; however multi-parametric methods using both viability and cytotoxicity markers may mitigate the inherent shortcomings of single parameter measures.

Assessment of different biomarkers provides valuable diagnostic standards in the evaluation of the risk of acute rejection

Acute rejection (AR) is a strong risk factor for chronic rejection in renal transplant recipients. Accurate and timely diagnosis of AR episodes is very important for disease control and prognosis. Therefore, objectively evaluated the immune status of patients is essential in the field of post-transplantation treatment. This longitudinal study investigated the usefulness of five biomarkers, human leukocyte antigen (HLA)-G5 and sCD30 level in sera, intracellular adenosine triphosphate (iATP) release level of CD4(+) T cells, and granzyme B/perforin expression in peripheral blood mononuclear cells (PBMCs) and biopsies, to detect AR and the resolution of biomarkers in a total of 84 cases of renal transplantation. The data demonstrated that recipients with clinical or biopsy proven rejection significantly increased iATP release level of CD4(+) T cells, and elevated sCD30 but lowered HLA-G5 level in sera compared with individuals with stable graft function. Expression levels of granzyme B and perforin were also elevated in PBMCs and graft biopsies of AR patients. Taken together, we identified that upregulation of sCD30, iATP, granzyme B, perforin, and downregulation of HLA-G5 could provide valuable diagnostic standards to identify those recipients in the risk of AR. And iATP may be a better biomarker than others for predicting the graft rejection episode.

The effects of early rapid corticosteroid reduction on cell-mediated immunity in kidney transplant recipients

While being helpful in the prevention and treatment of acute rejection (AR) in kidney transplant patients, corticosteroids have many side effects associated with their long-term use. It is reasonable to minimize these adverse effects without affecting their benefits. In this prospective trial, we investigated the effects of early rapid corticosteroid reduction on the cell-mediated immunity, measured by the Cylex® Immune Cell Function Assay, the incidence of AR and infection and the allograft function after kidney transplantation to assess the feasibility of this strategy in the Chinese population. A method of rapid reduction of corticosteroid to 10 mg/day seven days post-transplantation was adopted for the experimental group, and the standard corticosteroid therapy for the control group. Comparison of intracellular ATP values detected two weeks post-transplantation for the control group (324±45 ng/mL) and the experimental group (345±91 ng/mL) did not reveal a significant difference (p>0.05). The incidence of AR was analogous between groups (p>0.05), while an increased incidence of infection was observed in the control group (53%) versus the experimental group (22%), where p<0.05. The mean ATP concentration was lower in the control group (235±35 ng/mL) than that of the experimental group (286±16 ng/mL) when infection occurred (p<0.05). The mean allograft function was similar between groups (p>0.05). Rapid corticosteroid reduction early after kidney transplantation does not cause a significant rise in patient immunity or increase the incidence of AR, and contributes to infection control. This strategy may serve as a safe and effective therapy for kidney transplant patients in the Chinese population.

Intracellular ATP concentrations of CD4 cells in kidney transplant patients with and without infection

In the field of organ transplantation, overimmunosuppression is associated with severe side effects, such as infection, drug toxicity, and cancer, whereas underimmunosuppression is associated with acute rejection. Intracellular adenosine triphosphate (iATP) concentration following CD4 cell activation provides an assessment of cellular immune function to help monitor the immune status of immunosuppressed patients. This assay has shown to be the first post-transplant test related not only to the risk of acute rejection but also with the appearance of infection. The aim of our study was to compare the iATP concentrations of CD4 cells between healthy adults and kidney transplant recipients from a European population, analyzing the differences according to transplant clinical status. Samples from 81 kidney transplant patients who were admitted to our hospital over a nine-month period were drawn. T-cell activation was measured by determining the increase of iATP from CD4 cells. Results were compared with patient clinical status (rejection, infection, and stability). Three patients suffered an acute rejection episode and they were not included in the analysis (mean iATP concentration 247 +/- 87 ng/mL). iATP concentrations differed significantly between stable and infected patients (313 +/- 193 vs. 197 +/- 114 ng/mL; p = 0.008). iATP concentration values were not related to the length of admission, age, peak and current panel reactive antibodies, mismatches, leukocytes, weight, creatinine, days after transplantation and blood levels of cyclosporin, tacrolimus, and sirolimus. This assay measures global immune responses of CD4 T cells from a whole-blood sample, allowing for the assessment of the impact of immuno- suppressive drugs and of the patient's underlying clinical conditions. This assay identifies transplant patients at risk for infection or rejection, providing information which can guide immunosuppressive therapy.

Measurement of T-lymphocyte responses in whole-blood cultures using newly synthesized DNA and ATP

The proliferative response is most frequently determined by estimating the amount of [(3)H]thymidine incorporated into newly synthesized DNA. The [(3)H]thymidine procedure requires the use of radioisotopes as well as lengthy periods of incubation (>72 h). An alternative method of assessing T-lymphocyte activation in whole-blood cultures involves the measurement of the nucleotide ATP instead of [(3)H]thymidine incorporation. In addition, the Luminetics assay of T-cell activation measures specific T-lymphocyte subset responses through the use of paramagnetic particles coated with monoclonal antibodies against CD antigens. This assay permits rapid (24 h) analysis of lymphocyte subset activation responses to mitogens and recall antigens in small amounts of blood.

Bioluminescent assay for human lymphocyte blast transformation

One of the basic tests of in vitro evaluation of immune cell functional activity is a proliferative response of lymphocytes on the action of external stimuli such as mitogenic lectines, antigens, etc. We compared two methods used to assess the lymphocyte functional status. (1) [3H]thymidine incorporation and (2) bioluminescence for determination of intracellular ATP in blast cells. Comparison has been done for healthy donors and patients with proven low immunological status. The proposed bioluminescent method for evaluation of the proliferative response was shown to be sensitive enough for diagnostic purposes. This method allows one to process a large number of samples at the same time and correlates highly with the radionuclide test use hazardous radioactive materials.