Osteoclasts are multinucleated cells that resorb bone and are essential for bone homeostasis. OSCAR is a member of the leukocyte receptor complex (LRC) protein family that plays critical roles in the regulation of both innate and adaptive immune responses. Different from the other LRC members, OSCAR expression is detected specifically in preosteoclasts or mature osteoclasts. OSCAR may be an important bone-specific regulator of osteoclast differentiation. Multiple alternatively spliced transcript variants encoding different isoforms have been found for this gene. Recombinant human OSCAR protein, fused to His-tag at N-terminus, was expressed in E.coli.