The Innate and Adaptive Immune Functions of Osteoblast-Lineage Cells.

PURPOSE OF THE REVIEW: The osteoblast lineage has traditionally been viewed through a structural and metabolic lens, yet growing evidence indicates that these cells possess diverse functions, including roles in innate and adaptive immune responses. To establish a coherent mechanistic framework, we performed a systematic review of the literature concerning immune signalling, antigen presentation, and pathogen responses across the osteoblast lineage.

RECENT FINDINGS: We identified 463 unique studies, with 43 meeting the inclusion criteria. Our synthesis reveals a stage-specialised immune continuum. Osteoprogenitors appear to initiate early inflammatory signalling while mature osteoblasts operate as microbial sensors and conditional antigen-presenting cells via inducible expression of cell membrane and cytosolic pattern recognition receptors, and a functional major histocompatibility complex class II apparatus. Osteocytes, the most abundant and long-lived bone cell type, are also capable of detecting microbial danger and activate extensive interferon, chemokine and cytokine programmes within the lacunocanalicular network. Together, these properties define a stromal immune system that coordinates both innate and adaptive immunity across bone surfaces and the mineralised matrix. This osteoblast lineage-integrated immune architecture provides a conceptual basis for understanding osteomyelitis incidence and persistence, biomaterial-immune interactions, as well as inflammatory bone remodelling, reframing this lineage as a previously underappreciated regulator of skeletal and systemic immunity.