Cytokines and Cell Surface Receptors as Target End Points of Immunosuppression with Cyclosporine A

Abstract

Targets of cyclosporine (CsA) were identified from an array of stimulated lymphocyte responses (sLR) comprising 34 stimulation conditions in whole blood from 3 normal human volunteers (NHV) containing clinically relevant CsA concentrations (0-1200 ng/ml) in vitro. In whole blood from 5 additional NHV, selected targets (intracellular interleukin-2 [IL-2], tumor-necrosis factor-α [TNF-α], and interferon-γ [IFN-γ]) were measured in phorbol myristate acetate (PMA)-ionomycin-stimulated T lymphocytes. Effect:concentration relationships were analyzed with E_max pharmacodynamic (PD) equations and expressed as the concentration associated with one-half maximal inhibitory effect (EC₅₀). CsA demonstrated a rich matrix of inhibitory effects on T cells (CD3⁺), B cells (CD19⁺), dendritic cells (DC) (CD11c⁺), and basophils (CD123⁺) but not on monocytes (CD14⁺) (n = 3). PD analyses suggested that the EC₅₀ of CsA (1) for IL-2 in CD3⁺ cells in NHV (n = 8) was similar to the EC₅₀ demonstrated by us previously in CD4⁺ cells from transplanted patients (n = 13) (EC₅₀= 260 ng/ml vs. 249 ng/ml), (2) for each cytokine was different under identical stimulation conditions (TNF-α, 324 ng/ml; IFN-γ, 504 ng/ml), and (3) was relatively constant for a given cytokine under different stimulation conditions (e.g., PMA-ionomycin or the staphylococcal enterotoxin B [SEB] superantigen). In conclusion, inhibition of cytokine targets by CsA is concentration dependent. Further, a given CsA concentration may produce similar inhibitory effects across different stimulation conditions. Measurement of cytokine target expression may, therefore, allow effect-controlled administration of CsA during clinical transplantation.