IDENTIFICATION OF IL-16 AS THE LYMPHOCYTE CHEMOTACTIC ACTIVITY IN THEBRONCHOALVEOLAR LAVAGE FLUID OF HISTAMINE-CHALLENGED ASTHMATIC-PATIENTS

Objective: We have previously demonstrated that the earliest lymphocyt e chemotactic factors present in bronchoalveolar lavage fluid (BALF) o f subjects with atopic asthma after subsegmental antigen challenge are IL-16 and MIP-1 alpha, of which IL-16 appears to contribute a majorit y of the chemotactic activity. Because IL-16 is released in vitro afte r histamine stimulation of CD8+ T cells and epithelial cells, we evalu ated the potential role of histamine in the release of IL-16 into the airways of allergic asthmatics in vivo. Methods: Eight allergic asthma tic subjects, six normal subjects, and six atopic nonasthmatic subject s were challenged with saline in the lingula and with serial concentra tions of histamine (1 x 10(-7) to 5 x 10(-5) mol/L) in the right middl e lobe followed by bronchoalveolar lavage (BAL) 15 minutes and 6 hours later. Results: The BALF from saline- and histamine-challenged lobes of normal subjects and atopic nonasthmatic subjects contained no signi ficant lymphocyte chemoattractant activity. In six of the eight atopic asthmatic subjects, the histamine-challenged but not saline-challenge d segment contained IL-16 chemotactic activity but no other identifiab le lymphocyte chemoattractant activities at 6 hours. Conclusions: IL16 appears in the airways after histamine challenge and therefore could contribute to the earliest infiltration of CD4+ T cells and eosinophil s observed after antigen challenge due to histamine release from mast cells.