PDCD1 and autoimmune disease: The PD‐1/PD‐L1 pathway plays a critical role in the pathophysiology of autoimmune diseases, tumorigenesis, chronic infections, and inflammation.4 A recent study found that activation of the PD‐1/PD‐L1 pathway was associated with hyper‐activation of osteoclasts and impaired T‐cell proliferation in multiple myeloma.5 However, its role in osteoporosis has not yet been studied.