Aberrant or prolonged immune response has been proved to be involved in bone homeostasis.
As a component of the innate immune system, macrophages play a critical role in bone homeostasis.
Conventionally, according to response to the various panel of stimuli, macrophages can be
plastically classified into two major phenotypes: M1 and M2. M1 macrophages are generally proinflammatory,
whereas M2 are anti-inflammatory. Although studies have demonstrated that both M1
and M2 phenotypes have been implicated in various inflammatory bone diseases, their direct role in
bone homeostasis remains unexplored. Thus, in this review, we briefly discuss the term “osteoimmunology”,
which deals with the crosstalk and shared mechanisms of the bone and immune systems.
Besides, we overview M1 and M2 macrophages for their role in osteoclastogenesis and osteogenesis
as well as relevant signaling cascades involved.