IL-5 priming of the PMA-induced oxidative metabolism of human eosinophils from allergic and normal subjects during a pollen season

Aim To study the effect of IL-5 priming on the PMA-induced oxidative metabo lism of blood eosinophils from allergic patients and healthy controls, duri ng pollen exposure. Methods Twenty birch pollen allergic patients with seasonal symptoms of rhi nitis or rhinitis plus asthma were studied during the birch pollen season o f Sweden. Eosinophils were purified to > 95% by Percoll gradients followed by the MACS system. Oxidative metabolism was measured by a lucigenin enhanc ed chemiluminescence (CL) assay. Eosinophils were primed with IL-5 and subs equently stimulated with PMA. The signal transduction mechanisms of IL-5 pr iming were studied using the MEK inhibitor PD 98059, the PkC inhibitors Sta urosporine, Ro 318220, Go 6983 and the PI(3)kinase inhibitor Wortmannin. Results During the season, the eosinophils from the allergic patients showe d a reduced t(1/2)rise compared to the non-allergic controls (P = 0.019) af ter stimulation. IL-5 reduced the total PMA CL response both in control and patients' cells (P = 0.012 and 0.0054 resp.), whereas it primed it in term s of the t(1/2)rise of the curves, in both groups (P = 0.012 and 0.0015 res p.). The PMA-induced CL reactions were inhibited by PD 98059, all PkC-inhib itors and Wortmannin. IL-5 priming counteracted only the MEK inhibition sig nificantly. Conclusions Blood eosinophils from allergic patients are primed in vivo, as compared to eosinophils from non-allergic controls, during a pollen season . Interleukin-5 primes equally the PMA-induced oxidative metabolism of huma n eosinophils from healthy or allergic subjects. The mechanism of IL-5 priming after PMA stimulation of oxygen radical produ ction is MEK independent.