Soluble CD-4 and CD-8 as markers of immunological activation in renal transplant recipients

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Abstract
Background. T lymphocytes are activated following kidney transplantation in cases of acute graft rejection and viral infections. In plasma, elevated levels of T-cell markers can be measured in soluble form. The reason for this shedding is still not entirely understood. Methods. Plasma concentrations of soluble CD-4 and CD-8 (sCD-4, sCD-8) were determined in 78 patients following kidney transplantation by commercially available enzyme-linked immunosorbent assay (ELISA) test kits. Results. The concentrations of both soluble T-cell markers increased significantly in the course of acute allograft rejections and cytomegalovirus (CMV) infections. Frequently, the parameters increased shortly before clinical diagnosis and decreased under successful therapy. Additionally, sCD-8 showed significant higher plasma concentrations in cases of CMV infection as compared with acute allograft rejections. Accordingly, the sCD-4/sCD-8 ratio increased in cases of acute allograft rejection and decreased during CMV infections. Cyclosporin A nephrotoxicity caused no significant changes in the sCD-4 and sCD-8 levels in plasma. Conclusion. The present study demonstrates that sCD-4 and sCD-8 are markers of immunological activation and may enable a further differentiation of T-cell activation if serial measurements are performed. However, further prospective investigations are necessary to elucidate the diagnostic potential of sCD-4 and sCD-8 for monitoring acute rejection and viral infection in kidney graft recipients.