Differential reactivity of human bronchoalveolar lavage mast cells to substance P

Substance P (SP) stimulates human skin and rodent mast cells. Since neuropeptide-mediated reflexes may be important in asthma, the ability of SP to stimulate human mast cells obtained at bronchoalveolar lavage (BAL) was examined. Routine BAL (n = 22) samples were obtained and histamine release experiments performed in a standard manner. Spontaneous histamine release was bimodally distributed (Group A, high spontaneous release/Group B, normal spontaneous release). Further, Group A had significantly elevated corrected SP-induced histamine release compared to Group B but the corrected calcium ionophore A23187-induced responses were similar. No differences were found in clinical history, age, lavage return or total cell numbers between groups. However, differential cell counts revealed significantly elevated mast cell numbers in Group A providing further evidence for altered mast cell responsivity associated with mast cell hyperplasia. In asthma, BAL mast cells have increased spontaneous and stimulated secretory responses; thus, in asthma SP may also stimulate pulmonary mast cells.