PATIENTS WITH SEVERE ATOPIC-DERMATITIS HAVE ACTIVATED CIRCULATING BASOPHILS

Background: The purpose of this study was to define the potential role of the basophil in the pathogenesis of atopic dermatitis by comparing basophil releasibility in patients with food allergy and either mild or severe atopic dermatitis. Methods: A clinical scoring system was used to differentiate patients into either a low clinical score (LCS) group, 10 patients, or a high clinical score (HCS) group, 14 patients. Basophil histamine release was measured with a radioenzymatic assay, and leukotriene C4 (LTC4) was determined with a radioimmunoassay. Histamine and LTC4 released from basophils spontaneously or after incubation with deuterium oxide, an IgE-dependent histamine-releasing factor, anti-IgE, and C5a were measured Results: Basophils from the HCS group released more histamine than those from the LCS group when stimulated with deuterium oxide (median percent total release: 85% vs 68%, p < 0.05), with 10 and 100 ng/ml of anti-IgE (58% vs 26% and 62.5% vs 37%, both p < 0.05) and 5 and 50 ng/ml of C5a (50.5% vs 11.5, p < 0.05; 49% vs 11%, p < 0.01, respectively). The spontaneous release of LTC4 from basophils was greater in the HCS group (median release: 34 vs 3.5 pg/0.1 ml, p < 0.05). Basophils stimulated with deuterium oxide, with 100 ng/ml anti-IgE; and 50 ng/ml C5a released more LTC4 in the HCS group (111.5 vs 39 pg/0.1 ml, p < 0.05; 64.5 vs 10 pg.0.1 ml, p < 0.01; 80 vs 1 pg/0.1 ml, p < 0. 05, respectively). Conclusions: These data indicate that patients with more severe atopic dermatitis have ''activated'' circulating basophils in vivo and increased basophil releasibility in particular in response to C5a. These studies may serve as markers for more severe atopic dermatitis.