The complement system is a biochemical cascade which helps clear pathogens from an organism. It belongs to the innate immune system.<unk>  can be inherited or acquired (as a result of complement-consuming disease state). Complement deficiency states may predispose affected individuals to angioedema, collagen vascular disease, or infection due to encapsulated organisms, especially Neisseria meningitidis.
Complement deficiencies
Complement deficiency
IgG deficiency
Congenital defects of phagocytes
Natural killer cell deficiency
Leukocyte adhesion deficiency
Humoral immune deficiency
Phenocopies of primary immunodeficiency