Figure 5. A schematic of the proposed mechanism whereby CD38 negatively regulates osteoclast formation.
Contaminating lymphocytes, which highly express CD38, act as a NADase to cleave NAD+ present in the media into ADPribose. It is possible that a signal that increases the cyclase activity of CD38, or possibly CD157, may produce cyclic ADPribose, which will serve to enhance osteoclast formation.