Factor Bb is a protein that plays a crucial role in the body's immune response. It is part of the complement system, which helps the body fight infections and clear damaged cells. Factor Bb is formed when factor B is activated by factor D, and it works by promoting inflammation and attracting immune cells to sites of infection. In addition to its role in immunity, factor Bb is involved in the regulation of the alternative pathway of the complement system. This pathway is essential for the rapid response to pathogens. Abnormal levels of factor Bb can be associated with various diseases, highlighting its importance in maintaining health.