Longitudinal induced IL-2 mRNA monitoring in renal transplant patients immunosuppressed with cyclosporine and in unmodified canine renal transplant rejection.

Immune monitoring of transplant patients to define optimal immunosuppression continues to be important, as rejection occurs despite adjustment of dosaging of CsA or even FK506 to achieve "therapeutic-range" blood levels. Because CsA is known to inhibit upregulation of IL-2 mRNA transcription, we prospectively sequentially measured (induced) IL-2 mRNA in PHA-stimulated PBMC cultures from transplant recipients of kidneys from living-related donors (n = 15) using a quantitative PCR assay, with a potential 24-hour turnaround time, to define immunologic events in real time. Reproducible individual patient sensitivity or refractoriness to CsA was determined pretransplant, by adding a range of CsA concentrations to the PBMC cultures and constructing induced IL-2 mRNA regression inhibition curves. However, this was not predictive of rejection episodes, but did correlate well with individual differences in IL-2 mRNA levels posttransplant, despite similar maintenance trough blood concentrations of CsA between patients. In this prospective study, seven patients experienced rejection episodes despite therapeutic CsA trough levels. Three of these, plus one not receiving CsA therapy, who happened to be prospectively tested at the time that rejection was clinically diagnosed, had a decrease in induced IL-2 mRNA before treatment was instituted. As a correlation to this observation in patients, induced IL-2 mRNA levels in unmodified rejection were sequentially measured in PBMC cultures in autologous vs allogeneic canine renal transplants and IL-2, IL-10, TNF-alpha, and IFN-gamma mRNA were also measured in kidney biopsies. Sequential PHA lymphoproliferation assays of [3H] thymidine incorporation on patient and dog PBMC cultures were also performed. Similar to the observations in patients, unmodified rejection in the canine renal allograft model also was accompanied by a decline of PHA-induced IL-2 mRNA in PBMCs as the serum creatinine concentrations became elevated. In the dog kidney biopsies at later phases of rejection, IL-10 mRNA levels were also significantly elevated (p = 0.032).