A factor released by monocytes in the presence of dexamethasone stimulates neutrophil locomotion

1 Steroid‐treated monocyte supernatants cause a dramatic increase in the speed of locomotion of human neutrophils and a significant decrease in their adhesion to protein‐coated glass. In contrast, control monocyte supernatants have a smaller effect on the speed of locomotion, but cause a large increase in their adhesiveness. 2 This supernatant activity was produced equally well in the presence or absence of serum after 24 h culture at 37°C with 10−6 m dexamethasone. 3 The effect of the steroid‐treated monocyte supernatants on the speed of locomotion of human peripheral blood neutrophils was not altered by rabbit polyclonal antisera against lipocortins 1–6. 4 Rabbit anti‐interleukin‐8 antibody which blocked the effect of IL‐8 on the speed of locomotion of neutrophils did not antagonize the locomotion stimulating action of steroid‐treated monocyte supernatants. 5 The exocellular release of this factor(s) by human mononuclear leucocytes suggests that it may be an in vivo mediator of the anti‐inflammatory effect of glucocorticoids.