An intravascular chemoattractant lectin inhibits neutrophil migration.

KM+, a lectin purified from Artocarpusintegrifolia seeds, is an attractant for neutrophils, and has properties similar to fMLP, IL-8 and MNCF. The endogenous lectin MNCF, inhibits carrageenan-induced neutrophil migration when intravenously administered in rats. In an attempt to mimic the activity of MNCF with KM+, we determined the effect of intravenous (iv) injection of KM+ (5 microg) on neutrophil migration to the peritoneal cavity of Wistar rats induced by KM+ (50 microg, intraperitoneal, ip), fMLP (5 ng, ip) and carrageenan (300 microg, ip). Initially we evaluated the effect of the time interval between intravenous and intraperitoneal administration of KM+. The intervals ranged from 20 to 120 min and progressively stronger inhibition was observed with increasing time intervals up to a maximum of 60 min, with effect decreasing thereafter. With injections at the optimum interval of 60 min, we observed that KM+ inhibited KM+- and carrageenan-induced neutrophil migration by 72%, and fMLP-induced migration by 56%. White cell counts for Wistar rats that only received KM+iv, performed at 0 to 120 min intervals after injection, revealed early neutropenia lasting 60 min, followed by a marked increase in circulating neutrophils that reached a maximum of twice the initial levels within 90 min and after 120 min returned to levels near to that observed before intravenous administration of KM+. These results indicate that when KM+ is present in the intravascular space, it produces an inhibitory effect on neutrophil migration similar to that caused by the intravenous administration of other chemoattractants, regardless of whether they act through a mechanism independent of carbohydrate recognition, as does IL-8, or are dependent on carbohydrate recognition, like MNCF.