In vitro reactivity of mast cells in urticaria pigmentosa skin.

The aim of our study was to evaluate the sensitivity of skin mast cells from urticaria pigmentosa (UP) patients to substance P (SP), tumor necrosis factor alpha (TNF-alpha) and anti-IgE, and to compare the sensitivity of these cells with that of skin mast cells from healthy human donors. Mast cells for in vitro functional studies were obtained using an enzymatic dispersion technique from skin biopsies (from 11 patients with UP and 11 healthy donors), and the reactivity of these cells was estimated on the basis of histamine release. Our observations indicated that UP skin mast cells and healthy skin mast cells had similar sensitivities to challenge with TNF-alpha at a concentration 10(-7) M (16.4% vs 15.2%) and with anti-IgE at a dilution 1:100 (41.0% vs 37.0%). However, UP mast cells showed considerably higher sensitivity to challenge with SP at a concentration 10(-4) M than healthy skin mast cells (20.0% vs 6.8%), and the difference was statistically significant (P < 0.001). UP skin mast cells also demonstrated significantly higher spontaneous histamine release than healthy skin mast cells (32.1% vs 12.4%, P < 0.001). Our findings indicating UP skin mast cell sensitivity to SP might suggest that mechanisms involving neurogenic inflammation could contribute to the course of this disease.