Defining the signaling and downstream regulation of neutrophil-dendritic cell development for adjunctive therapy

Abstract Neutrophils are typically considered short-lived and terminally differentiated. However, recent studies have identified a poorly understood neutrophil subset that can differentiate into dendritic cells and become long-lasting “hybrids” of neutrophils and dendritic cells. These neutrophil-dendritic cells (PMN-DCs) maintain the functions of canonical neutrophils while gaining antigen-presenting properties of dendritic cells, enabling them to contribute to both innate and adaptive immunity. Although PMN-DCs have been characterized in various inflammatory conditions, the cues that drive their development are not fully understood. Granulocyte macrophage colony-stimulating factor (GM-CSF) has previously been implicated as an important signal for PMN-DC development in studies of murine and human neutrophils. In vivo neutralization suggests that GM-CSF is sufficient but not necessary to drive PMN-DC differentiation. To determine the requirement of GM-CSF we have deleted GM-CSF receptor using CRISPR editing of a murine neutrophil progenitor cell line. We have tested other implicated cytokines in vitro, including IL-3, IL-4, TNF-α and IFN-γ, however these signals alone do not induce differentiation of PMN-DCs but can augment or blunt PMN-DC differentiation. Previous work shows that PMN-DCs are potent effectors of antifungal immunity through both direct killing and antigen presentation; understanding of the developmental signals that drive PMN-DC differentiation is essential for any future therapies targeting PMN-DCs.