The potent osteoclastogenic agent, tumor necrosis factor-α (TNF), exerts its biological effects
via two receptors, namely TNF receptors 1 (p55r) and 2 (p75r), each present on osteoclast
precursors. Thus, we asked if p55r and p75r differentially impact the osteoclastogenic
process. Marrow derived from mice expressing only p55r generates substantially more
osteoclasts, in the basal state, than does wild type, while marrow expressing only p75r,
produces substantially fewer. Reflecting its preferential activation of p55r, exogenous TNF …