TNF-α-dependent loss of IKKβ-deficient myeloid progenitors triggers a cytokine loop culminating in granulocytosis

Loss of I kappa B kinase (IKK) beta-dependent NF-kappa B signaling in hematopoietic cells is associated with increased granulopoiesis. Here we identify a regulatory cytokine loop that causes neutrophilia in Ikk beta-deficient mice. TNF-alpha-dependent apoptosis of myeloid progenitor cells leads to the release of IL-1 beta, which promotes Th17 polarization of peripheral CD4(+) T cells. Although the elevation of IL-17 and the consecutive induction of granulocyte colony-stimulating factor compensate for the loss of myeloid progenitor cells, the facilitated induction of Th17 cells renders Ikk beta-deficient animals more susceptible to the development of experimental autoimmune encephalitis. These results unravel so far unanticipated direct and indirect functions for IKK beta in myeloid progenitor survival and maintenance of innate and Th17 immunity and raise concerns about long-term IKK beta inhibition in IL-17-mediated diseases.