Analysis of the Survival of Mature Human Eosinophils: Interleukin-5 Prevents Apoptosis in Mature Human Eosinophils

Abstract

AbstractWe and other groups have previously shown that interleukin-5 (IL-5) maintained the viability of mature eosinophils in an in vitro liquid culture system. Mature eosinophils did not proliferate but their survival was maintained in the presence of IL-5. Using this culture system, we investigated the mechanism of IL-5–mediated survival. In the absence of human IL-5 (hlL-5) mature eosinophils succumbed after 4 days, while in the presence of hlL-5 they survived up to 10 days. When DNA extracts of cultured eosinophils were analyzed on an agar gel electrophoresis, marked DNA fragmentation was observed in the absence of hlL-5, while no significant DNA fragmentation was observed in the culture with hlL-5 for 48 hours. The DNA fragmentation appeared as early as 6 to 12 hours after hlL-5 deprivation. Concomitantly, IL-5 stimulated total RNA and protein synthesis, but did not induce DNA synthesis in mature eosinophils. Because cycloheximide or actinomycin D impeded the protection of apoptosis by hlL-5, some new RNA and protein synthesis appeared to be required in this phenomena. These findings indicate that IL-5 maintains survival of mature eosinophils with induction of new RNA and protein synthesis, thus leading to the inhibition of apoptosis.