Association of IL-5 cytokine production and in vivo IgE levels in infants and parents

Background: Total IgE in human subjects tracks strongly from birth onward through unknown mechanisms. Regulation of IgE might occur in relation to adaptive immune cytokine production. In vitro studies have assessed the role of individual cytokines in regulating IgE production in human subjects. Objective: We sought to investigate the association between IgE levels in vivo and the capacity of the individuals to produce adaptive immune cytokines. Methods: Blood samples from participants in the Tucson Infant Immune Study (children at birth and at 3 and 12 months of age, fathers, and mothers before and after delivery) were assessed for percentage of eosinophils and plasma total IgE levels. IFN-γ, IL-4, IL-5, IL-13, and IL-10 levels were measured in supernatants of mitogen-stimulated PBMCs and examined cross-sectionally for relation to cytokine production by using simple regression, multiple regression with cytokines only and with other known predictors of IgE levels, and longitudinally by means of random effects modeling. Results: After adjusting for eosinophils and other predictors, IL-5 production (but not that of other cytokines) was associated directly with total IgE levels in children at 3 months (P = .009) and 12 months (P = .011) of age but not at birth. The IL-5/IgE association was present also in fathers (P = .040) and in mothers, both during pregnancy (P < .001) and after delivery (P = .030). Conclusions: This study indicates that mitogen-stimulated IL-5 production is associated with in vivo total IgE levels, independent of the production of other cytokines and circulating eosinophils. Clinical implications: Understanding the regulation of IgE in vivo might help elucidate the development of allergic responses in individuals.