β₂-glycoprotein I, the major target in antiphospholipid syndrome, is a special human complement regulator.

The human plasma protein β(2)-glycoprotein I (β(2)-GPI) is the major target of autoantibodies associated with antiphospholipid syndrome. However, the biologic function of this abundant protein is still unclear. Here we identify β(2)-GPI as a complement regulator.

The yeast Candida albicans evades human complement attack by secretion of aspartic proteases.

Candida albicans, which represents one of the most important human pathogenic yeasts, is directly attacked by the host innate immune system upon infection. However this pathogen has developed multiple strategies to escape host immune defense. Here, we show that C.

Factor H-related protein 1 (CFHR-1) inhibits complement C5 convertase activity and terminal complex formation.

Homozygous deletion of a 84-kb genomic fragment in human chromosome 1 that encompasses the CFHR1 and CFHR3 genes represents a risk factor for hemolytic uremic syndrome (HUS) but has a protective effect in age-related macular degeneration (AMD). Here we identify CFHR1 as a novel inhibitor of the complement pathway that blocks C5 convertase activity and interferes with C5b surface deposition and MAC formation. This activity is distinct from complement factor H, and apparently factor H and CFHR1 control complement activation in a sequential manner.