This figure represents the complement system and the various pathways involved in the cascade. The<unk><unk><unk>  <unk> -INH) enzyme plays a role in the classical pathway of the complement cascade, which is a component of the immune system response that acts to protect the human body from a variety of foreign substances. As shown in the figure above, the complement cascade starts with the<unk> q protein which binds to an antibody-antigen complex that arises during an immune response to an invading substance. When the complex is signaled for activation, or turned on, then downstream proteins in the complement cascade are activated, including complement component 2 (C2), complement component 3 (C3), and complement component 4 (C4). When these particular enzymes such as C3 and C4 are activated, their subsequent signals lead to an inflammatory response that involves localized edema, or swelling. The role of<unk> -INH is to regulate and control the activities of the complement cascade, such that complement proteins remain in check and do not lead to unnecessary activity. When there is a deficiency of<unk> -INH due to one of the previously mentioned causes, then the complement cascade remains continuously activated and can lead to potentially life-threatening swelling.
Acquired C1 esterase inhibitor deficiency
Hereditary angioedema
Terminal complement pathway deficiency
Type IV hypersensitivity
IgG4-related skin disease
Complement 3 deficiency
Type III hypersensitivity
Complement 2 deficiency