Mast cells produce ENA-78, which can function as a potent neutrophil chemoattractant during allergic airway inflammation.
The inflammatory response during allergic airway inflammation involves the recruitment of multiple leukocyte populations, including neutrophils, monocytes, lymphocytes, and eosinophils. All of these populations likely contribute to the pathology observed during repeated episodes of allergic airway inflammation. We have examined the role of a human neutrophil-specific chemokine (C-x-C), ENA-78, in a model of allergic airway responses and identified murine mast cells as a cellular source of an ENA-78-like molecule. Within this allergic airway model, neutrophil infiltration into the airway occurs within 4-8 h post-allergen challenge, persists within the airway until 24 h, and resolves by 48 h post-challenge. Neutrophil influx precedes the eosinophil infiltration, which peaks in the airway at 48 h post-allergen challenge. In this study the production of ENA-78 from challenged lungs demonstrated a significant increase in the allergen-, but not vehicle-, challenged lungs. In vivo neutralization of ENA-78 by passive immunization demonstrated a significant decrease in peak neutrophil infiltration at 8 h, with no effect on the eosinophil infiltration at 48 h post-challenge. Because ENA-78 has been shown to be chemotactic for neutrophils and given the involvement of mast cell degranulation in allergic responses, we examined mast cells for the presence of ENA-78. Cultured mast cells spontaneously released ENA-78, but on activation with IgE + antigen, NG-L-arginine methyl ester or compound 48/80 produced significantly increased levels of ENA-78. Supernatants from sonicated MC-9 mast cells induced an overwhelming influx of neutrophils into the BAL by 4 h post-intratracheal injection into mice, suggesting that the mast cell is a significant source of neutrophil chemotactic factors. Mast cell supernatant-mediated neutrophil infiltration was substantially decreased by preincubation of the supernatant with antibodies specific for ENA-78. These data indicate a major neutrophil chemotactic protein produced by mast cells during allergic responses may be mast cell-derived ENA-78.