Table 1

Biological activities of complement activation proteins, with relevance to AD.

Name
Biological activity

C1q
Enhances Aβ aggregation [43,44]; may facilitate Aβ clearance [56]; enhances Aβ-induced cytokine secretion by microglia [49]
C3a
Anaphylatoxin (increases capillary permeability) [155] ; protects neurons vs. excitotoxicity [52]
C3b
Immune adherence and opsonization [89] (may facilitate Aβ clearance by phagocytic microglia)
C4a
Anaphylatoxin (weak) [156]
C5a
Anaphylatoxin; protects neurons vs. excitotoxicity [51]; chemotaxic attraction of microglia [46,47]; inhibits apoptosis 54; increases cytokine release from Aβ-primed monocytes [48]
C5b-9
Neurotoxicity [50]; sublytic concentrations may have both pro- and anti- inflammatory activities [157]

Loeffler Journal of Neuroinflammation 2004 1:18   doi:10.1186/1742-2094-1-18