Complements are group of proteins that are involved in inflammation. The activation of the complements occur in the following settings:
Systemic Lupus
Glomerulonephritis
Complement deficiencies
Complement levels of C3, C4, and CH50 usually can indicate complement activation. CH50 indicates activity of the overall complement system. There are nine major complement proteins but C3 and C4 are the ones measured frequently because of their position in both classical and alternate complement activation pathways and are also most abundant.
C3 and C4 levels can be low in systemic lupus. Low complements along with elevated double-stranded DNA along with proteinuria and active urinary sediment indicate presence of lupus nephritis.
TeachMeMedicine.Org 