Despite its strengths, the original C3D has limitations:
When the complement pathway is activated by foreign antigens, C3 is cleaved into C3a and C3b. Inactivation of C3b by regulatory enzymes triggers a sequential degradation process: C3b is broken down into iC3b (inactive C3b). iC3b is processed further into C3dg. Despite its strengths, the original C3D has limitations: