A CD4-lineage erythro-myeloid progenitor within the adult bone marrow defines an alternative pathway for macrophage generation.

A CD4-lineage erythro-myeloid progenitor (EMPROR) in adult bone marrow generates macrophages via an alternative pathway, independently of CCR2-mediated monocyte recruitment.

• Why it matters: Adult replenishment of tissue-resident macrophages is thought to rely exclusively on circulating monocytes, leaving an untested gap for other adult progenitor sources.
• What they did: The study identifies EMPROR cells lacking Csf1r and Ccr2 but expressing Cd4 and Kit, using single-cell RNA sequencing, RNA velocity, and lineage assays.
• The result: EMPROR cells produce perivascular and tumor-associated macrophages independently of CCR2-mediated monocyte recruitment and also contribute to erythroid and granulocytic lineages under inflammatory and neoplastic conditions.