EOTAXIN INDUCES A RAPID RELEASE OF EOSINOPHILS AND THEIR PROGENITORS FROM THE BONE-MARROW

The CC-chemokine eotaxin is a potent eosinophil chemoattractant that s timulates recruitment of eosinophils from the blood to sites of allerg ic inflammation. Mobilization from the bone marrow is an important ear ly step in eosinophil trafficking during the allergic inflammatory res ponse, In this paper we examine the potential of eotaxin to mobilize e osinophils and their progenitors from bone marrow, Eotaxin stimulated selective, dose-dependent chemotaxis of guinea pig bone marrow eosinop hils in vitro, Intravenous injection of eotaxin (1 nmol/kg) into guine a pigs in vivo stimulated a rapid blood eosinophilia (from 3.9 +/- 1.2 to 28 +/- 9.9 x 10(4) eosinophils/mL at 30 minutes) and a correspondi ng decrease in the number of eosinophils retained in the femoral marro w (from 9.0 +/- 0.8 to 4.8 +/- 0.8 x 10(6) eosinophils per femur), To show a direct release of eosinophils from the bone marrow an in situ p erfusion system of the guinea pig femoral bone marrow was developed, I nfusion of eotaxin into the arterial supply of the perfused femoral ma rrow stimulated a rapid and selective release of eosinophils into the draining vein, In addition, eotaxin stimulated the release of colony-f orming progenitor cells, The cytokine interleukin-5 was chemokinetic f or bone marrow eosinophils and exhibited a marked synergism with eotax in with respect to mobilization of mature eosinophils from the femoral marrow, Thus, eotaxin may be involved in both the mobilization of eos inophils and their progenitors from the hone marrow into the blood and in their subsequent recruitment into sites of allergic inflammation. (C) 1998 by The American Society of Hematology.