Deficiency of Complement
Complement plays an important role in the well-being of humans. Deficiency of various components may result in many diseases as follows:
1. Inherited deficiency of C1 esterase inhibitors causes angio-edema. The low level of C1 esterase inhibitors leads to over-production of esterase. This leads to an increase in release of anaphylatoxins, which cause capillary permeability and edema.
2. Acquired deficiency of DAF results in an increase in com-plement-mediated hemolysis. The condition manifests clinically as paroxysmal nocturnal hemoglobinuria.
3. Inherited or acquired deficiency of C5–8 components greatly enhances susceptibility to Neisseria bactere-mia and other infections. Deficiency of C3 leads to severe recurrent pyogenic sinusitis and respiratory infections.
4. The synthesis of sufficient quantities of complement is reduced in the patients with severe liver disease, such as chronic hepatitis or alcoholic cirrhosis. These patients, therefore, are highly susceptible to infections caused by pyogenic bacteria.
Deficiency of complement components and diseases associ-ated with these complement deficiency are summarized in Table 15-2.