REGULATION OF THE PRODUCTION OF THE RANTES CHEMOKINE BY ENDOTHELIAL-CELLS - SYNERGISTIC INDUCTION BY IFN-GAMMA PLUS TNF-ALPHA AND INHIBITION BY IL-4 AND IL-13

Production by endothelial cells of the regulated on activation normal T expressed and secreted chemokine (RANTES) has recently been evidence d during delayed-type hypersensitivity (DTH) reactions and may contrib ute to the local accumulation of macrophages and CD4(+) memory T lymph ocytes. To document the mechanism inducing RANTES production in this c ondition, we analyzed the effect of cytokines known to influence the f ormation of DTH granulomas. Little or no RANTES was produced after sti mulation of HUVEC with IFN-gamma, IL-1 beta, or TNF-alpha. However, th e combination TNF-alpha+IFN-gamma induced a strong RANTES production. In situ hybridization experiments with a RANTES probe showed that this synergy was also observed at the mRNA level and that the effect of th e combination was mainly to increase the amount of RANTES mRNA per cel l. The expression of the luciferase gene under the control of the RANT ES gene regulatory elements was analyzed; TNF-alpha and the combinatio n TNF-alpha+IFN-gamma activated the regulatory elements. Sequential tr eatment of HUVEC with TNF-alpha and IFN-gamma showed that IFN-gamma se nsitized HUVEC to the stimulating effect of TNF-alpha. The production of RANTES induced by TNF-alpha+IFN-gamma was partly but significantly inhibited by the Th2-type cytokines IL-4 and IL-13. In contrast, IL-10 had no effect. These results indicate that the microenvironment of DT H granulomas, containing high levels of both TNF-alpha and IFN-gamma, may be responsible for RANTES production by perigranulomatous endothel ial cells. Inhibition of this production by Th2-type cytokines may be a mechanism by which these cytokines interfere with the formation of D TH granulomas.