Significant Reduction of ATP Production in PHA-Activated CD4+ Cells in 1-Day-Old Blood from Transplant Patients

Background. Global immunosuppression can be measured by assessing adenosine triphospate (ATP) levels in mitogen-stimulated CD4+ T cells. Methods. We investigated the effect of storage time on ATP levels in 234 blood samples from 18 healthy individuals and 152 transplant patients. The difference between day 0 (<13 hours post-blood draw) and day 1 (24-37 hours) measurements was analyzed and compared with various factors; a subset of samples was also analyzed in 6-hour intervals. Results. The ATP levels were significantly lower on day 1 compared with that on day 0 in healthy individuals (279 +/- 159 vs 414 +/- 159 ng/mL, P<0.001) and patients (356 +/- 209 vs 455 +/- 221 ng/mL, P<0.0001). Of the 18 healthy individuals, 17 showed ATP reduction, whereas 192 (89%) of 216 patients did so on day 1 (24.8 +/- 24.1%). In the time course analysis, ATP levels decreased with the blood storage time in healthy and patient samples, and the reduction began as early as 7 hours post-blood draw. The reduction rate was significantly higher in patient samples with low day 0 ATP levels compared with samples with moderate or high levels (44.7 +/- 31.3% vs 23.2 +/- 23.6% or 18.7 +/- 15.7%; P<0.001). The reduction rate in patients treated with alemtuzumab induction was slightly higher than that in daclizumab-treated patients (28.8 +/- 24.6% vs 21.3 +/- 21.3%, P=0.09). CD4+ cell number did not change within 24 hours post-blood draw, but CD4 expression decreased 2.0 +/- 2.8% (P<0.05). Conclusions. The ATP levels are significantly lower in 1-day-old blood compared with fresh blood, suggesting that fresh blood should be used for assessing the T cell immune function to obtain the most accurate results.