Fig. 1

Dendritic cell (DCs) subtypes involved in bone homeostasis and disease. DCs are a highly heterogeneous population of antigen-presenting cells (APCs) that can be classified into distinct subpopulations based on their ontogeny, phenotype, and function. DCs originate from bone marrow myeloid progenitor cells (MDPs) derived from hematopoietic stem and progenitor cells (HSPCs). These progenitors can give rise to common dendritic cell progenitors (CDPs), which further differentiate into two major types: conventional DCs progenitors (pre-cDCs), which develop into cDCs in the periphery, and plasmacytoid DCs progenitors (pre-pDCs), which differentiate into pDCs in the bone marrow. Other subtypes of DCs, including Langerhans cells (LCs) and interstitial DCs (intDCs), are localized in the epithelium, while bone marrow DCs (BMDCs) are found in the bone marrow. Additionally, inflammatory DCs (infDCs) are present at peripheral inflammation sites. Functionally, immature DCs (iDCs) can encounter danger signals, resulting in their maturation into mature DCs (mDCs) and promotion of immune responses. Conversely, when iDCs encounter self-antigens without sufficient co-stimulatory signals, they differentiate into tolerogenic DCs (tolDCs) and induce immunomodulation. Mo monocyte, RBC red blood cell