Release of neutrophil chemotactic activity during immediate hypersensitivity reactions in humans.

Heat-stable, serum-derived chemotactic activity for neutrophils is shown in a human model of immunoglobulin E-mediated asthma. Twenty-six ragweed-sensitive subjects underwent bronchial provocation challenge using ragweed and Mecholyl. Increased neutrophil chemotactic activity was found in serum tested from 5 to 30 min after a positive ragweed-inhalation challenge, but not after negative ragweed challenge. The appearance of neutrophil chemotactic activity did not reflect the effects of bronchospasm alone, because it was not found after bronchospastic responses to Mecholyl in the same subjects. There were no accompanying changes of serum complement activity, nor evidence of inhibition of the chemotactic activity by proir exposure to antisera to the third and fifth components of complement. Ultrafiltration of serum showed chemotactic activity contained in fractions of at least 50 000 daltons. This appears to be the first demonstration of neutrophil chemotactic activity liberated during experimentally induced immunoglobulin E-mediated asthma in humans.