Abstract NF-κB inducing kinase (NIK), an upstream regulator of the noncanonical NF-κB signaling pathway, is implicated in the development of Hypereosinophilic-like syndrome (HES) in mice. HES in human patients is defined by 1.5x109 cells/L circulating in the blood with end-organ infiltration and resultant tissue damage. In mice lacking the NIK gene (Map3k14), the mechanisms underlying eosinophilopoiesis have not been fully elucidated, although previous studies have demonstrated a connection between Th2 helper T cells and HES in Nik-/- mice. We hypothesize that NIK also influences the development and education of eosinophils in the hematopoietic tissues independent of T-cell involvement. We developed an in vitro bone marrow microenvironment, and utilized MTT and BrdU assays coupled with cytology, flow cytometry, BCL-XL ELISA, and an inflammation antibody array to show that Nik-/- eosinophils demonstrate altered metabolism, survival, and maturation when compared to wild type eosinophils in response to an altered microenvironment and cytokine milieu. Furthermore, the Nik-/- in vitro bone marrow microenvironment contains lower levels of free TNFR1 and more consistent surface bound TNFR1 when compared to wild type counterparts. Additionally, we explored the heterogeneity of granulocyte differentiation in the Nik-/- model. Here, we demonstrate that in vivo, Nik-/- mice contain significantly higher counts of both mature and immature eosinophils, and a population of eosinophils expressing neutrophil marker Ly6G, which may represent a unique population subset of eosinophils. Overall, these data indicate that NIK influences eosinophil maturation, differentiation, and responsiveness to the surrounding microenvironment.
Trusiano et al. (Thu,) studied this question.