Human blood polymorphonuclear neutrophils (PMN) are thought to be involved in the pathogenesis of asthma through their recruitment into the bronchoalveolar lumen and the lung by local release of chemotactic factors. Therefore chemotactic activities of several mediators (PAF, histamine and three neuropeptides substance P, VIP and a somatostatin analog) were compared on blood PMN from both healthy subjects (HS) and asthmatic patients (AP). The maximal response to PAF was significantly different (P less than 0.05) with cells from both groups. Moreover activity for the HS peaked at 10(-6) M, whereas the AP showed peak chemotactic activity at 10(-8) M. Histamine had no chemoattractant effect on PMN. Substance P did not induce PMN locomotion, whereas VIP induced a chemotactic response in a dose-dependent manner, particularly with cells from HS as compared to those from AP. BIM 23014 (a somatostatin analog) exhibited chemotactic activity which was also more pronounced with PMN from HS as compared to those from AP. Our findings showed that blood PMN could be involved in asthma through their heightened locomotor reactions to mediators which are known to be released locally by activated cells in bronchoalveolar lumen.