It is activated by the binding of immune complexes (antibody-antigen complexes) to C1q, which recruits C1r and C1s to cleave C4 and C2. This leads to the formation of the C3 convertase (C4b2a), which cleaves C3 into C3a and C3b.
It is activated by the binding of immune complexes (antibody-antigen complexes) to C1q, which recruits C1r and C1s to cleave C4 and C2. This leads to the formation of the C3 convertase (C4b2a), which cleaves C3 into C3a and C3b.