PRODUCTION OF INTERLEUKIN-8 (IL-8) BY CULTURED ENDOTHELIAL-CELLS IN RESPONSE TO BORRELIA-BURGDORFERI OCCURS INDEPENDENTLY OF SECRETION IL-1AND TUMOR-NECROSIS-FACTOR-ALPHA AND IS REQUIRED FOR SUBSEQUENT TRANSENDOTHELIAL MIGRATION OF NEUTROPHILS

Previous studies have shown that Borrelia burgdorferi, the spirochetal agent of Lyme disease, promotes inflammation by stimulating endotheli al cells to upregulate adhesion molecules for leukocytes and to produc e a soluble agent that is chemotactic for neutrophils. We determined t hat interleukin-8 (IL-8) was the chemotactic agent for neutrophils pre sent in conditioned media from cultured human umbilical vein endotheli al cells stimulated with B. burgdorferi, As few as one spirochete per endothelial cell stimulated production of IL-8 within 8 h of coincubat ion. When 10 spirochetes per endothelial cell were added, IL-8 was det ected after 4 h of coculture, Production of IL-8 continued in a linear fashion for at least 24 h, Neutralizing antibodies against IL-8 reduc ed migration of neutrophils across spirochete-stimulated endothelial m onolayers by 93%, In contrast, pretreatment of neutrophils,vith antago nists of platelet-activating factor did not inhibit migration, Increas es in production of IL-8 and expression of the adhesion molecule E-sel ectin by endothelial cells in response to B. burgdorferi were not inhi bited by IL-1 receptor antagonist or a neutralizing monoclonal antibod y directed against tumor necrosis factor alpha, used either alone or i n combination. These results suggest that activation of endothelium by B, burgdorferi is not mediated through the autocrine action of secret ed IL-1 or tumor necrosis factor alpha, Rather, it appears that B, bar gdorferi must stimulate endothelium either by a direct signaling mecha nism or by induction of a novel host-derived proinflammatory cytokine.