This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pharmacology
DENOSUMAB a monoclonal antibody against RANKL receptor is used in the treatment of ? 
Select and explain. 
A. Rheumtoid ahritis, B. Osteoporosis, C. Osteoahritis, D. SLE
B: Osteoporosis
Answer: B: Osteoporosis 
Explanation: Ans. is 'b i.e., Osteoporosis Donesumab o Osteoclast is a cell responsible for bone resorption. o Osteoclasts express RANK receptors on its surface (RANK --> receptor activator for nuclear factor). o When RANK receptor combine with their ligands (RANKL) osteoclastogenesis is initiated and bone resorption occurs. o Donesumab is a monoclonal antibody against RANK ligand. o It prevents the activation of the osteoclasts by these ligand. Note : o Osteoporosis is a disease characterized by decrease in the bone mass. o In osteoporosis there is increase in the osteoclast activity and there is increased expression of RANK and RANKL.