Synergistic effect of IL-1α, IFN-γ, and TNF-α on RANTES production by human renal tubular epithelial cells in vitro

Interstitial rejection of renal allografts is associated with infiltrating mononuclear cells. Mechanisms leading to this mononuclear cell influx are still not fully resolved, The chemokine RANTES (Regulated upon Activation, Normal T cell Expressed and Secreted) is chemotactic for monocytes and T cells. In renal allograft biopsies of patients undergoing rejection, RANTES is found in infiltrating monocytes and T cells, as well as in the tubular epithelium. This study analyzes the production of RANTES in vitro by proximal tubular epithelial cells (PTEC) after stimulation with the inflammatory cytokines interleukin-1 alpha, (IL-1 alpha), interferon-gamma (IFN-gamma), and tumor necrosis factor-alpha (TNF-alpha). Unstimulated PTEC or PTEC stimulated with the cytokines IL-1 alpha, IFN-gamma, and TNF-alpha alone did not produce detectable amounts of RANTES. However, a combination of IFN-gamma and either IL-1 alpha or TNF-alpha resulted in strong induction of RANTES production up to 2046 +/- 817 pg/ml or 2595 +/- 525 pg/ml per 1 x 10(5) PTEC, respectively. After stimulation with IL-1 alpha and TNF-alpha. RANTES production was less prominent than the combination of IFN-gamma with either IL-1 alpha or TNF-alpha. and only detectable in 5 of 7 PTEC lines tested. The production of RANTES was both dose- and time-dependent and was inhibited by cycloheximide, indicating that de novo protein synthesis is required. Because the production of RANTES by PTEC is more pronounced in the presence of T cell-derived IFN-gamma (in combination with either IL-1 alpha or TNF-alpha), it was hypothesized that RANTES produced by PTEC presumably plays a prominent role in the amplification phase of the immune response rather than in the initiation phase.