The human BAFF protein, or B-cell activating factor, is a crucial cytokine that plays a significant role in regulating the immune system and promoting B-cell survival and maturation. BAFF is primarily produced by immune cells, including monocytes, macrophages, and dendritic cells. It binds to specific receptors on B cells, allowing their development and preventing apoptosis (cell death). BAFF also influences the production of antibodies and helps regulate the balance of different B-cell subsets.