OBJECTIVE To examine whether ligation of the adhesive receptors - selectin L and Mac-1 on the neutrophil surface could induce gelatinase B exocytosis. METHODS Neutrophils were isolated from fresh heparinized blood of human donors by Gradisol G centrifugation and hypotonic lysis of erythrocytes. METHODS Integrin CD1 1b/CD18 and selectin L mediated adhesive interaction of human neutrophils were mimicked by binding antibodies to these receptors on the surface of isolated leukocytes. Neutrophils (5 x 10(6)/ml) were incubated with antibodies against selectin L (40/microg/ml) and CD18 or CDI 1b (10microg/ml). The secretion of gelatinase was examined by determination of enzyme activity and gelatin substrate zymography of cell supernatants. RESULTS Ligation of selectin L, CD18 and CD11b integrin subunits by monoclonal antibodies induced a rapid release of 24.6+/-1.8% (p<0.005), 24.0+/-2.9% (p<0.001) and 22.7+/-2.0% (p < 0.005) of total neutrophil gelatinase, respectively as compared with 11.1+/-1.6% in the control. These values were equivalent to N-formyl-methionylleucyl-phenylalanine (fMLP)-stimulated secretion of gelatinase. Under these experimental conditions there was no significant beta-glucuronidase release from azurophilic granules. Gelatinase exocytosis elicited by selectin L and CD18 ligation was inhibited by 82.7+/-10.1% and 49.3+/-5.9%, respectively after preincubation of the neutrophils with 10 microM herbimycin A. CONCLUSIONS Ligation of selectin L and integrin CD11b/ CD18 provides stimulatory signals to neutrophils which induce secretion of gelatinase B that may facilitate their transmigration into sites of inflammation.