Article thumbnail
Location of Repository

T-Cell Receptor-Stimulated Calcineurin Activity Is Inhibited in Isolated T Cells from Transplant Patients

By James A. Tumlin, Brian R. Roberts, Kenneth E. Kokko, Osama El Minshawy and Jennifer L. Gooch


The addition of calcineurin inhibitors, including cyclosporine A (CsA) and FK-506 (tacrolimus), to transplant protocols has markedly reduced acute allograft rejection and prolonged patient survival. Although monitoring of serum drug levels has been shown to be a poor indicator of efficacy, there is little data on calcineurin enzymatic activity in humans. Therefore, we measured calcineurin in isolated CD3+/4+ T cells from 81 non-transplant controls and 39 renal allograft patients by using a 32PO4-labeled calcineurin-specific substrate. A gender difference was observed in the control cohort, with activity in males significantly higher than that in females (1073 ± 134 versus 758 ± 75 fmol/μg/min, respectively). Activity of both groups was comparably inhibited by 5 ng/ml tacrolimus (27 ± 4 versus 30 ± 4%). Calcineurin is a downstream target of the T-cell receptor (TCR). Therefore, activity was measured in isolated T cells after incubation with anti-CD3/CD28 antibodies to stimulate the TCR. Calcineurin activity increased significantly from 1214 ± 111 to 1652 ± 138 fmol/μg/min; addition of either tacrolimus or CsA (500 ng/ml) blocked CD3/CD28 stimulation. Despite therapeutic levels of tacrolimus and CsA (mean 11.4 and 172 ng/ml), basal calcineurin activity was significantly higher among renal transplant recipients than controls (1776 ± 175 versus 914 ± 78 fmol/μg/min). In contrast, anti-CD3/CD28 antibodies failed to stimulate calcineurin activity in transplant subjects. Finally, we found that basal and stimulated calcineurin activities are inversely related. Consistent with this finding, basal activity in resting T cells rose over time after transplant but stimulation fell (r2 = 0.785, p < 0.05). These data suggest that examination of TCR-stimulated calcineurin activity after renal transplantation may be useful for monitoring immunosuppression of individual patients

Topics: Gastrointestinal, Hepatic, Pulmonary, and Renal
Publisher: American Society for Pharmacology and Experimental Therapeutics
OAI identifier:
Provided by: PubMed Central
Download PDF:
Sorry, we are unable to provide the full text but you may find it at the following location(s):
  • http://www.pubmedcentral.nih.g... (external link)
  • Suggested articles

    To submit an update or takedown request for this paper, please submit an Update/Correction/Removal Request.