356 CD9 — An activity marker on eosinophils in platelet containing blood?

HES is characterized by peripheral blood eosinophilia, but the cause is unknown.To investigate the pathophysiology of HES, we examined 12 patients with HES.Eusinophil counts of the patients were 1680-48720/pl.Pereoll density eantrifugation of eosinophils revealed that 50~8% of patients' eosinophils were hypodeuse, compared to 9+3% from normal individuals (n=12).These hypodense eosinopbils survived longer in vitro without exogenous cytokines than normodense eosinophils from the same patients or eosinophils from normal donors (45±11, 6+4, and 9±5% of survival after 4 days in culture, respect/rely), and exogenous IL-5 minimally enhanced survival of patients' eosinophils.Sera from 6 of 12 patients, but none of 12 normals, enhanced survival of normal eosinophils, and the effects were neutralized by anti-IL-5 antibody; sere of the other 6 patients did not enhance eusinophil survival.Serum levels of IL-5 in the patients were less than 20 pg/ml in 9 patients, 20-30 pg/ml in 2 patients, and 150 pg/ml in I patient (compare to normals <20 pg/ml and patients with angioedema with eosinophilia >700 pg/ml).There was no correlation between the serum concentrations of IL-5 and blood eosinophil counts.Furthermore, enhanced PBMC production of 1L-5, when stimulated by PHA, was observed in 3 of the 8 patients tested.These results suggest that the persistent eosinophilia in HES is not likely due to elevated blood IL-5 in most of the cases, and that intrinsic abnormality of eosinophilopoiesis may be the cause of the disease.