Autologous serum skin test reactivity in patients with non-allergic asthma

Background Inflammatory alterations of respiratory airways have been found in patients with non-allergic asthma, but the triggering event has not been defined. An autoimmune activation of inflammatory cells has been hypothesized. Objective To evaluate whether histamine-releasing factors are present in sera from non-allergic asthmatics. Methods Twenty-four patients with non-allergic asthma underwent in vivo autologous serum skin test (ASST) and in vitro basophil histamine release assay using autologous basophils as well as basophils from normal donors. Twenty-seven subjects with respiratory allergy and three normal subjects were chosen as control. Results ASST was positive in 14/24 non-allergic asthmatics (58%) whereas it was negative in all 30 control subjects (P < 0.001). The serum of only one ASST-positive patient out of 12 (8.4%) induced in vitro histamine release from autologous basophils. The serum from another ASST-positive patient induced histamine release from membrane IgE-stripped autologous basophils. Sera from either non-allergic asthmatics or from control subjects did not provoke significant histamine release from basophils from three normal donors. Conclusion Skin reactivity to autologous serum is common among non-allergic asthmatics, indicating the presence of circulating histamine-releasing factors. However, only in a minority of patients in vitro functional evidence of histamine-releasing autoantibodies (anti-Fc epsilon RI or anti-IgE) was obtained. The presence of circulating histamine-releasing factors might contribute to initiation/maintenance of inflammation in respiratory airways of non-allergic asthmatics.