Effects of skin-chamber fluids from human allergic reactions on neutrophil activation

We have found activated neutrophils (PMNs) in skin chambers overlying the site of ongoing human allergic reactions. To determine whether this activation is due to component(s) released early in these IgE-mediated reactions, we investigated the in vitro effects of skin chamber fluids (CF) on resting blood PMNs. These skin CF had been previously obtained, at different time periods, at pollen-antigen-challenged or buffer-control-challenged sites in sensitive human subjects. PMNs incubated with CF obtained during the first hour of antigen challenge (first-hour CF) generated significantly more superoxide (O₂^-) than spontaneous production (p<0.001) and more than PMNs incubated with first-hour buffer-site CF (p<0.002). A pattern similar to O₂^- generation was observed in lactoferrin secretion during the incubation of the three cell aliquots described above (p<0.001). After these incubations, the subsequent responsiveness of the PMNs present in the cell buttons to opsonized zymosan, a PMN activator, was assessed. PMNs previously incubated with first-hour CF generated significantly more net O₂^- in response to opsonized zymosan than did PMNs previously incubated with first-hour buffer-site CF (p<0.001) or buffered saline (p<0.001). Again, a similar difference in the patterns of net lactoferrin secretion was observed (p<0.02). These events were not associated with PMN damage. Analogous studies with CF previously obtained during the second- to first-hour of antigen or buffer challenge stimulated much less than first-hour CF. We conclude that one or more components released early in IgE-mediated skin reactions can activate PMNs. The nature of the activating component(s) is unknown, with no evidence of activation by histamine, antigen, or other components found to date in first-hour CF.