Circulating stem cell factor in patients with chronic idiopathic urticaria

Background: The nature of histamine-releasing factors involved in the pathogenesis of chronic idiopathic urticaria (CIU) is still controversial, since functional IgG autoantibodies specific for the high-affinity IgE receptor, FcepsilonRI, can be detected in only 20% of patients showing a strong skin reactivity on the autologous serum skin test. The absence of systemic eosinophilia in CIU patients, along with the increase in mast cells in skin biopsy specimens, suggests a possible role for stem cell factor (SCF), the only cytokine/growth factor known to induce mediator release from human mast cells. Objective: To investigate the possible role of SCF as a histamine-releasing factor in patients with CIU. Methods: The SCF levels were measured in serum samples from 65 patients with CIU who scored strongly positive on the autologous serum skin test; of these patients, 32 had negative results and 33 had positive results on in vitro histamine release assay by a quantitative commercial sandwich immunoassay technique. Serum samples from 40 healthy subjects were used as controls. Results: Serum SCF levels in all 65 CIU patients did not differ from those found in healthy controls. No difference in SCF levels was found between patients with positive and negative results on histamine release assay. Conclusions: An increase in serum SCIF levels does not play a pathogenic role in CIU.