Wang, H.-B.Weller, Peter2017-08-142008Wang, H.-B., and P. F. Weller. 2008. “Pivotal Advance: Eosinophils Mediate Early Alum Adjuvant-Elicited B Cell Priming and IgM Production.” Journal of Leukocyte Biology 83 (4) (January 22): 817–821. doi:10.1189/jlb.0607392.0741-5400http://nrs.harvard.edu/urn-3:HUL.InstRepos:33747053Alum, aluminum-hydroxide-containing compounds, long used as adjuvants in human vaccinations, functions by ill-defined, immunostimulatory mechanisms. Antigen-free alum has been shown to act via a previously unidentified, splenic Gr1+, IL-4-expressing myeloid cell population to stimulate early B cell priming. We demonstrate that the alum-elicited and -activated splenic myeloid cells are IL-4-expressing eosinophils that function to prime B cell responses. Eosinophils are the principal Gr1+, IL-4+ cells in the spleens 6 days following i.p. alum administration. Alum-elicited splenic B cell priming, as evidenced by MHC II cross-linking-mediated calcium mobilization developed in wild-type BALB/c mice, was absent in ΔdblGATA BALB/c eosinophil-deficient mice and could be reconstituted by adoptive eosinophil infusions into the eosinophil-deficient mice. Moreover, early antigen-specific IgM antibody responses in alum-antigen-immunized mice were impaired in eosinophil-deficient mice and were restored with adoptive transfers of eosinophils. Thus, eosinophils, leukocytes of the innate immune system that contain preformed cytokines, including IL-4, have novel, immunomodulatory roles in the initial priming of B cells elicited by the adjuvant alum and in the optimal early B cell generation of antigen-specific IgM.en-USJournal Article10.1189/jlb.0607392