A B S T R A C T A heat-stable neutrophil chemotactic factor (NCF) has been identified in the serum of 13 atopic asthmatic subjects after treadmill exercise. Peak activity was detected at 10 min and returned to prechallenge values by 1 h. No NCF activity was detected in the sera of three nonasthmatic atopic or four normal nonatopic individuals performing the same task. NCF produced by exercise (NCFEX) had a similar timecourse of release to NCF provoked by specific antigen (NCFAG). The appearance of circulating NCFEX and NCFAG closely paralleled the fall in peak expiratory flow rate/forced expiratory volume in 1 s (PEFR/ FEVI). Histamine challenge in atopic asthmatics at concentrations giving a comparable change in PEFR/ FEVy to that evoked by exercise or inhaled antigen was not associated with the appearance of circulating NCF. In seven subjects NCFEX release was inhibited by prior administration of disodium cromoglycate. NCFEX and NCFAG eluted as single peaks of activity when applied separately to columns of Sephadex G-200, and both were an estimated 750,000 daltons. NCFEX and NCFAG also eluted as single peaks of activity, at between 0.15 and 0.30 M NaCl, following anion exchange chromatography on DEAE-Sephacel (pH 7.8). The isoelectric points of NCFEX and NCFAG were virtually identical (between pH 6.0 and 6.5) as determined by chromatofocusing on Polybuffer Exchanger 94. The activities of NCFEx and NCFAG were substantially reduced, in both a time-and dose-dependent fashion, after incubation with trypsin and chymotrypsin. Partially purified NCFEX and NCFAG promoted both stimulated random migration (chemokinesis) as well as directional migration (chemotaxis).These experiments indicate that NCFEX and NCFAG might be identical substances and raise the possibility

Human alveolar macrophages (AM) were obtained from eight normal volunteers using fiberoptic bronchoscopic lavage to explore potential interrelationships among leukocytes in pulmonary defense against infection. AM placed in monolayer tissue cultures released material into culture supernatants with the capacity to enhance the bactericidal capacity of human neutrophils. Neutrophils preexposed to supernatants killed Pseudomonas aeruginosa from 70 to 90% more efficiently than control cells (P < 0.02). AM culture supernatants contained this material by 4 h of incubation, and in vitro stimulation of AM cultures with heat-killed P. aeruginosa further increased its production.Gel filtration of AM culture supernatants with a G-50 Sephadex column allowed isolation of a 6,000-D neutrophilactivating factor (NAF) that was resistant to heat (56°C, 30 min). The isoelectric point of NAF, as determined by chromatofocusing, was -7.6. Enzyme digestion of NAF specimens, prepared sequentially by gel filtration and chromatofocusing, demonstrated 50-70% loss of activity after incubations with trypsin, chymotrypsin, and neuraminidase. NAF was only minimally chemotactic and eluted from Sephadex G-50 with particles of a different molecular size than those of AMderived chemotactic factors (i.e., -10,000 D and <500 D). Preincubation of neutrophils with NAF resulted in greater release of superoxide anion upon their subsequent stimulation by either bacterial phagocytosis or by phorbol myristate acetate, as compared with control neutrophils stimulated in a like manner. These studies indicate that human AM secrete a heatstable, low molecular weight basic protein, with the capacity to enhance oxidative microbicidal activity of neutrophils.