KEGG   DISEASE: Alternative complement pathway component defects
H00104                      Disease                                
Alternative complement pathway component defects
Factor B deficiency
Factor D deficiency
Factor H deficiency
Properdin deficiency
Disorders of innate immunity [DS:H02525]
Primary immunodeficiency disease [DS:H01725]
The alternative pathway 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.
Primary immunodeficiency
Human diseases [BR:br08402]
 Immune system diseases
  Primary immunodeficiency
   H00104  Alternative complement pathway component defects
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
hsa04610  Complement and coagulation cascades
CFB [HSA:629] [KO:K01335]
CFD [HSA:1675] [KO:K01334]
CFH [HSA:3075] [KO:K04004]
CFP [HSA:5199] [KO:K15412]
Other DBs
ICD-11: 4A00.1
OMIM: 615561 613912 609814 312060
Pettigrew HD, Teuber SS, Gershwin ME
Clinical significance of complement deficiencies.
Ann N Y Acad Sci 1173:108-23 (2009)
Kumar A, Teuber SS, Gershwin ME.
Current perspectives on primary immunodeficiency diseases.
Clin Dev Immunol 13:223-59 (2006)
Geha RS, Notarangelo LD, Casanova JL, Chapel H, Conley ME, Fischer A, Hammarstrom L, Nonoyama S, Ochs HD, Puck JM, Roifman C, Seger R, Wedgwood J.
Primary immunodeficiency diseases: an update from the International Union of Immunological Societies Primary Immunodeficiency Diseases Classification Committee.
J Allergy Clin Immunol 120:776-94 (2007)

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