Phosphatidic acid increases C5b-7 uptake and lysis by C5b-9. Various concentrations of phosphatidic acid were incorporated into erythrocytes in the presence of vanadate. The cells were washed and used in a hemolytic assay to determine percent lysis (○). The same cells were used to measure uptake of C5b-7 using¹²⁵I-C7 (•). Lysis before the addition of C8 and C9 varied between 0% for the buffer control and 18% for the highest concentration of DPPA.