Binding of HNP-1 to C1q (▪), C1r/C1s (▴), C1-inhibitor (▾), C1 (○), and BSA (⧫). Microtiter plates were coated with 1 μg C1q, C1r/C1s, intact C1, C1-inhibitor, or BSA and incubated with increasing concentrations of HNP^Biotin. After washing, bound HNP^Biotin was detected by subsequent incubation with streptavidin-HRP and ABTS. Optical density was measured and plotted.