Immunoglobulin-like receptors (IgLR) , expressed in a wide range of cells in immune system, provide a positive and negative regulation of immune responses. Activation signals initiated by activating IgLR associating with ITAM-containing adapter proteins DAP12 and FcRγ are indispensable for the development of osteoclasts. On the other hand, ITIM signals induced by inhibitory IgLR regulate osteoclast development and activation. Thus, ITAM and ITIM play important roles in the maintenance of bone homeostasis.