Figure 2.

Both classical and alternative complement components are required for efficient uptake of apoptotic cells. The efficiency of phagocytosis of autologous neutrophils was compared in 15% human serum that was selectively deficient in the complement components C1q, C3, Factor B, or C9 (Sigma Chemical Co.). To verify that a specific complement component was responsible for the effect observed, add-back experiments were performed with the missing factor (C1q, 250 μg/ml; Factor B, 250 μg/ml; or C9, 60 μg/ml [Sigma Chemical Co.]). d, deficient. The mean ± SD of four experiments is shown.