Nemours Biomedical Research, Molecular Genetics, Cellular and Tissue Transplantation, Wilmington, DE 19803, USA.

In children, therapeutic management of immunosuppression relies on allograft function, drug levels, and clinical insight. Using a Food and Drug Administration-approved test for T-cell response, T-cell activation in vitro can be measured to monitor the immune response.

In a retrospective study, 92 posttransplant children who received either a liver and/or kidney transplant and were followed by routine screening had their T-cell response tested by the Cylex ImmuKnow assay (Columbia, MD). After phytohemagglutinin-L stimulation of T-cells, adenosine triphosphate (ATP) concentrations were measured. In this assay, light emission at lambda = 562 nm is proportional to the ATP concentration (ng/mL). Immunosuppressive drug trough levels were also measured. Quantitative real-time polymerase chain reaction Epstein-Barr virus (EBV) viral titers were determined for 2 patients.

Separating the results into younger than 12 years and 12-year or older populations, we found that for the younger than 12 years, 28% of patients were in the low immune function category, 47% in the moderate, and 25% in the high category. For the 12 years or older, 25% of patients were in the low immune function category, 47% in the moderate, and 28% in the high category. The immune function distribution was not different (P = not significant) between the younger than 12 years and 12-year or older groups. Tacrolimus trough levels were 6.3 +/- 2.4 ng/mL for younger than 12 years and 5.6 +/- 3.3 ng/mL for 12 years or older (P = not significant), and rapamycin was similar, but both showed no correlation to immune function. We observed increased ATP values with decreased EBV viral loads.

These results suggest that tacrolimus and/or rapamycin levels do not adequately determine the biologic effect of immunosuppression. We expect that future T-cell activation monitoring will allow us to diminish rejection and infection events posttransplantation and lead to a healthier pediatric transplant population.

Written by
Sampson VB, Dunn SP, Rymeski B, Malatack J, Rong NH, Flynn L, Krueger LJ.

Reference
J Pediatr Surg. 2008 Jun;43(6):1134-41.
doi:10.1016/j.jpedsurg.2008.02.044

PubMed Abstract
PMID:18558196

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