Relation of interleukin-6 in rheumatoid arthritis patients to systemic bone loss and structural bone damage.

IL-6 plays a key role in local and systemic manifestation of RA. IL-6 is not only a pro-inflammatory cytokine, but also interacts in complex ways with the cells involved in bone remodeling. In RA, IL-6 may indirectly promote osteoclastogenesis by increasing the release of RANK-L by osteoblasts, and it diminishes the proliferation of osteoblasts at late differentiation stages.