C3b deposition is a critical step in the complement activation pathway, which enhances opsonization and promotes phagocytosis of pathogens. Factor H plays a significant role in regulating this process by acting as a cofactor for the decay-accelerating activity of complement regulators.
Factor H binds to C3b on the surface of pathogens and promotes its cleavage by factor I, which converts C3b into iC3b. The presence of Factor H thus slows down the accumulation of C3b on pathogen surfaces by facilitating its inactivation, ensuring that complement activation does not become dysregulated, which is essential for preventing damage to host tissues.
Other factors listed, such as Factor P, Factor D, and Factor B, have different roles in the complement cascade. Factor P (properdin) stabilizes the alternative pathway C3 convertase, enhancing complement activation, while Factor D is involved in cleaving Factor B to form the C3 convertase. Factor B is a structural component of the C3 convertase and is necessary for complement activation but does not directly slow down C3b deposition.
Thus, Factor H is critical in controlling the balance of complement activation at the site of infection by regulating C3b deposition.