Assessment of immunosuppression by serum inhibition of alloreaction and measurement of cyclosporin A (CyA) serum levels in kidney graft recipients under CyA

Abstract

Abstract. The immunosuppressive effect of kidney graft recipient sera was studied on T-lymphocyte alloreactive line (4H) proliferation and compared to native cyclosporin A (CyA) and CyA metabolite concentrations determined by radioimmunoassay (RIA) using specific or nonspecific monoclonal antibodies. Three clinical groups were studied: (1) patients experiencing acute renal rejection episodes (CyA-R), (2) patients experiencing CyA-dependent nephrotoxicity episodes (CyA-TOX) and (3) patients in a clinically steady state (CyA-ST), according to their therapeutic regimen i. e., monotherapy (CyA alone) or polytherapy (CyA associated with prednisolone and/or azathioprine). Regardless of the clinical state, sera of patients in polytherapy displayed more inhibitory activity than those of monotherapy patients (24% and 40% inhibition of 4H proliferation, respectively, at sera dilution of 1:2), something which was no doubt due to the inhibitory activity of prednisolone on T-lymphocyte growth. In the two therapeutic regimens, CyA-ST patient sera exhibited the lowest inhibitory activity on the 4H line (45% and 65% inhibition of 4H proliferation in mono-and polytherapy, respectively, at sera dilution of 1:2). Sera from CyA-TOX patients were highly inhibitory (74% and 86% inhibition of 4H proliferation in mono-and polytherapy, respectively, at sera dilution of 1:2), in agreement with RIA assays showing increased native circulating CyA and CyA metabolites and daily CyA intake in this group as compared to CyA-ST. Surprisingly, CyA-R patient sera were no less inhibitory than those of CyA-ST patients on 4H-line, antigen-induced proliferation. This clinical group did not differ from others for CyA intake or level of circulating immunosuppressive molecules, suggesting that rejection could be associated with a state of interin-dividual variation in sensitivity to CyA. In addition, a polytherapeutic regimen seemed to modify CyA bioavailability in CyA-ST group patients, with a decreased CyA metabolite level as compared to their monotherapy counterparts (native CyA plus metabolite/native CyA ratio being 2. 73 and 3. 73, respectively). In contrast, in the CyA-R patient group, polytherapy appeared to be associated with an increase in CyA metabolite circulating levels (ratio 4. 79). In view of the low inhibitory activity of CyA metabolites, this profile might lead to rejection.