Increased expression and release of functional tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) by T cells from lupus patients with active disease

Increased expression of TRAIL in membrane-bound and soluble form in patients with systemic lupus erythematosus (SLE) has been previously reported. In this study, we characterized the upregulation of T-cell-associated and soluble TRAIL (sTRAIL) in vivo and the modulation of TRAIL expression and soluble protein release in vitro following T cell activation and IFNα exposure. The expression of membrane-bound TRAIL as determined by flow cytometry was higher on CD4⁺ and CD8⁺ T cells from lupus patients compared to controls, particularly on activated CD69⁺CD8⁺ T cells. Similarly, sTRAIL levels determined by ELISA were significantly elevated in serum from patients with active SLE and correlated with levels of IFNα. In vitro, both T-cell-associated and sTRAIL were maximally induced by T cell activation plus IFNα in patients and controls. By Western blot analysis, sTRAIL was detected in sera in both the monomeric and multimeric, functional form. Both forms of TRAIL were functional in vitro as determined by Annexin V staining and ⁵¹Cr release assay but the apoptotic activity of membrane TRAIL was 2.5-fold higher compared to that of sTRAIL. These results indicate that IFNα-induced enhancement of TRAIL expression and of TRAIL-mediated apoptosis may amplify the abnormal apoptotic process in SLE.