Chemokines such as monocyte chemoattractant protein (MCP) -1 and interleukin (IL)-8 are known to be involved in various processes in atherosclerosis such as plaque formation, plaque rupture, and thrombus formation. We investigated whether a new chemokine, Leukotactin (LKN)-1, is involved in atherosclerosis. We tested the expression of LKN-1 by immunohistochemical methods in carotid atherosclerotic plaque specimen. Induction of pro-inflammatory cytokines, transmigration, and tissue factor (TF) expression were tested in THP-1 cells and human peripheral blood monocytes treated with recombinant human LKN-1. Immunohistochemical analyses revealed that expression of LKN-1 occurs in regions of plaques rich in foam cells. In a Boyden chamber assay, THP-1 cells treated with 0.01--10 nM of LKN-1 transmigrated through gelatin coated filters in a dose dependent manner. LKN-1 also induced the transient expression of TNF-alpha, IL-8, and MCP-1 within 15 min of the treatment of the THP-1 cells. When peripheral blood monocytes were treated with LKN-1, expression levels of TF and TF-mediated procoagulating activity were induced in a time- and dose-dependent manner. These results raise the possibility that LKN-1 is another chemokine that is involved in the atherogenesis. LKN-1 may chemoattract immune cells into the plaque, induce pro-inflammatory cytokines, and produce thrombi by inducing TF expression.