Age-Related Changes in Eosinophil Function in Human Subjects

BackgroundAging results in changes in immune cell function that have been described for T-cells, macrophage, neutrophils, and dendritic cells but not for eosinophils. We sought to define age-related changes in eosinophil function and their potential implications for asthma.MethodsWe recruited human subjects with asthma in two age groups: a younger group (20 to 40 years), and an older group (55 to 80 years). Lung function, induced sputum, and peripheral blood were obtained from each subject. Eosinophils isolated from the peripheral blood were examined for in vitro functional activities including degranulation, superoxide anion production, adhesion, and chemotaxis.ResultsEosinophil degranulation in response to interleukin-5 stimulation was significantly decreased in the older group (p = 0.025). Eosinophil production of superoxide anions in response to phorbol myristate acetate was lower in the older group but did not achieve statistical significance (p = 0.097). Eosinophil adhesion, eosinophil chemotaxis, lung function, and the percentage of sputum eosinophils were similar in the two groups.ConclusionAirway eosinophilia is comparable in younger and older asthma subjects. However, there are age-related changes in peripheral blood eosinophil “effector” functions. Diseases such as asthma, in which eosinophils are thought to play a pathophysiologic role, may exhibit important clinical differences in the elderly due to age-related changes in inflammatory cell function that affect the manifestations of the disease and/or responsiveness to specific classes of medications.