Skin eosinophilia in patients with allergic asthma, patients with nonallergic asthma, and healthy controls: II: 20-hydroxy-leukotriene B4 is a potent in vivo and in vitro eosinophil chemotactic factor in nonallergic asthma

Abstract

Background: In allergic and nonallergic asthma, eosinophils play an important effector role. However, because the pathogenesis of these types of asthma seems different, the mechanisms responsible for the tissue mobilization of those cells may be different. The in vivo and in vitro migratory response of eosinophils from patients with allergic and nonallergic asthma toward 20-hydroxy-leukotriene B, (20-OH-LTB 4), which is reported here, illustrates this. Methods: By means of the Rebuck skin window technique the in vivo skin mobilizing capacity of intracutaneously applied buffer, LTB 4, and 20-hydroxy (OH)-LTB 4 was evaluated in healthy subjects ( n = 6), subjects with allergic asthma ( n = 14), and subjects with nonallergic asthma ( n = 17). Also the in vitro chemotactic responsiveness of eosinophils from the circulation of both patient groups (both n = 8) toward buffer, LTB 4, and 20-OH-LTB 4 were tested by use of a microchemotaxis chamber technique. Results: Although none of the substances were capable of inducing macroscopic observable skin reactions, intracutaneously applied 20-OH-LTB 4 had an almost similar capacity to mobilize eosinophils in the skin of the subjects with nonallergic asthma as allergens had in subjects with allergic asthma. In 92% of the tested subjects with nonallergic asthma significant skin eosinophilia was observed. By contrast, LTB 4 did not induce significant skin eosinophilia in both patient groups compared with buffer solution. This in vivo eosinophil mobilizing capacity of 20-OH-LTB 4 in subjects with nonallergic asthma was confirmed by in vitro chemotaxis studies. Dose ranges of both LTB 4 and 20-OH-LTB 4 proved to be potent chemoattractants for eosinophils from patients with nonallergic asthma, but not for those of healthy subjects and those with allergic asthma. Conclusions: Our results indicate that 20-OH-LTB 4 may be involved in the tissue mobilization of eosinophils in nonallergic asthma and that in vitro 20-OH-LTB 4 (and LTB 4) may act as potent chemotactic factors on eosinophils from those patients.