What is the primary function of Factor D in the complement system?

Factor D plays a critical role in the complement system by cleaving Factor B, which is essential for the formation of the alternative pathway C3 convertase. When Factor D encounters the complex of C3b and Factor B, it catalyzes the cleavage of Factor B into two fragments: Ba and Bb. This cleavage is pivotal because the Bb fragment then combines with C3b to form the C3 convertase (C3bBb), which is crucial for the activation of C3, leading to enhanced opsonization, inflammation, and cell lysis.

Understanding the mechanism of Factor D emphasizes its importance in regulating and advancing the cascade of events that occurs during immune responses. This role is fundamental in recognizing how the complement system can amplify its effects against pathogens, highlighting the interconnected nature of the components within the immune system.