Increased expression and activation of CD30 induce apoptosis in human blood eosinophils

Eosinophils are one of the major effector cells in asthma, and controlling the number and survival of eosinophils might attenuate the severity of asthma. This result could be achieved by inducing eosinophil apoptosis. Apoptosis allows the removal of cells without inducing an inflammatory response. Our knowledge of the factors involved in regulating eosinophil apoptosis remains limited. CD30 molecule has been associated with T cell-negative selection and in TCR-mediated apoptosis. In this study we examined the expression and role of CD30 in apoptosis of human blood eosinophils. Percentage of apoptotic eosinophils was determined by annexin V-propidium iodide labeling, and CD30 expression was examined by flow cytometry. Spontaneous apoptosis was induced by serum deprivation, and survival was conferred by incubating cells with 10% FBS and IL-5. CD30 surface expression was up-regulated in eosinophils incubated for 24 h as compared with freshly isolated eosinophils, and both CD30 expression and eosinophil apoptosis increased in a time-dependent manner. We also measured CD30 mRNA expression by quantitative real-time RT-PCR and determined that CD30 transcripts increased in eosinophils undergoing apoptosis only under serum deprivation conditions. The agonistic CD30 Abs, Ber-H8 and HeFi-1, significantly enhanced eosinophil apoptosis. FBS and IL-5 failed to inhibit or suppress the CD30 agonistic-induced apoptosis. These data support the role of CD30 activation in eosinophil apoptosis. This research will help in furthering our understanding of eosinophil apoptosis and therefore might contribute to the development of better therapeutic modalities in the treatment and/or cure of allergic inflammation in bronchial asthma.