Complement Deficiency

Excerpt

The immune system is the body’s defense mechanism against infections and is made of two pathways - the innate pathway and the adaptive pathway. The innate pathway is present from birth and is pre-programmed. The innate immune system consists of the cellular component, which includes monocytes, macrophages, and natural killer cells, and the humoral component, which includes the complement system. The adaptive pathway develops during life with exposure to infection and increases affinity with experience. It consists of the cellular component, which is T cells, and the humoral component, which consists of antibodies made by B cells. The adaptive pathway facilitates improved destruction of the organism as well as forms memory cells for future infections.

Complement deficiencies are primary immunodeficiencies that cause various clinical scenarios depending on the specific complement protein that is deficient. This can include an increased risk of a wide range of infectious as well as local or systemic inflammatory and thrombotic conditions.

Additionally, the complement system does not only act as the defense mechanism against infections it also works as a mediator in both the prevention of immune complex-related diseases and pathogenesis, such as systemic lupus erythematosus (SLE).