CSF1 and cytomegalovirus infection: In a mouse model of hematopoietic stem cell transplantation, these authors demonstrate that the cytokine macrophage colony‐stimulating factor (M‐CSF; also known as CSF‐1) protects from lethal murine CMV infection through the activation of a coordinated myeloid‐natural killer (NK) cell differentiation program that reconstitutes antiviral activity, leading to viral clearance without impairing stem cell engraftment.