However, T lymphocytes [23, 24] and natural killer cells [25] have been reported to contribute to osteoporosis by their activation and production of osteoclastogenic cytokines, but the observation that various T cell subtypes can exhibit either osteoclastogenic, e.g., Thy 17, or antiosteoclastogenic activity, e.g., Thy1 [26], suggests that there is a balance between pro- and antiosteoclastic activity in T cell subtypes. The gene discussed is THY1; the disease is osteoporosis.