DISEASE: Alternative complement pathway component defects
Entry
H00104 Disease
Name
Alternative complement pathway component defects
Subgroup
Factor B deficiency Factor D deficiency Factor H deficiency Properdin deficiency
Supergrp
Disorders of innate immunity [DS:H02525] Primary immunodeficiency disease [DS:H01725]
Description
The alternative pathway (AP) is antibody independent and relies on native C3 undergoing minimal spontaneous hydrolysis. Hydrolyzed C3 binds factor B. Factor B, when bound to hydrolyzed C3, is cleaved by factor D into Ba and Bb. Hydrolyzed C3Bb is responsible for a constant low level of C3 cleavage into C3b. If C3b binds to an appropriate surface, factor B will bind with C3b to form C3bBb, a highly efficient C3-cleaving enzyme. This overall series of successive proteolytic steps is enhanced by the serum protein properdin, which stabilizes protein:protein interactions during the process. Factor H is essential in controlling the function of the alternative pathway by inhibiting the formation of and degrading C3bBb. Deficiencies of alternative pathway-specific components are rare, and usually lead to an increased frequency of Neisseria infections.
Category
Primary immunodeficiency
Brite
Human diseases in ICD-11 classification [BR:br08403]
04 Diseases of the immune system
Primary immunodeficiencies
4A00 Primary immunodeficiencies due to disorders of innate immunity
H00104 Alternative complement pathway component defects
Pathway-based classification of diseases [BR:br08402]
Immune system
nt06513 Complement cascade
H00104 Alternative complement pathway component defects
Primary immunodeficiency diseases: an update from the International Union of Immunological Societies Primary Immunodeficiency Diseases Classification Committee.
