Tetranectin is a recently described human plasma protein, which is found in most secretory cells throughout the body, including neutrophils. We present evidence for the presence of tetranectin in human monocytes and macrophages as well, and that these cells upon adherence or weak stimulation release a 20 kDa protein identified as tetranectin by immunoblotting. The amount of tetranectin released is 3-18 ng/h/10(6) monocytes. The possible influence of tetranectin on cellular functions was tested in migration and oxidative metabolism assays. Monocyte spontaneous migration was significantly stimulated by preincubation with purified tetranectin, whereas chemotactic and chemiluminescence responses to fMLP and C5a were unchanged. Neutrophil functions were not affected. It is concluded that tetranectin is secreted from human mononuclear phagocytes upon weak stimulation, and that the secreted tetranectin facilities spontaneous migration of these cells.