EAC4 and EAC14 production without purified Ci

EAC4 and EAC14 of high activity were prepared by treating sensitized red cells with human or guinea pig serum in the presence of TTHA, a chelating agent whid at low pH to maximize C1 and C4 activity and to minimize C3 contamination. Cells prepared with guinea pig complement were contaminated with C2, which could be decayed away at 37 degrees C. Cells sensitized with IgG antibody were more reactive than those sensitized with whole serum or with IgM, and preparations made with TTHA-complement were more reactive than those prepared with purified C1 plus EDTA-complement. EAC14 stored at 0 degrees C for 3 weeks lost very little activity.