FIGURE 3.

Complement activation mediated by IgG1 and IgG3 is cell type–dependent. (A) Complement-dependent cytotoxicity (CDC) activity of IGHG1*03 (black), IGHG3*01 (long hinge, red), and IGHG3*04 (short hinge, pink) specific to trinitrophenyl (TNP) on RBCs at various Ag densities of 0.25 mM (low), 0.5 mM (medium), and 1 mM (high) TNBS in the presence of 20% serum. (B) CDC activity of same anti-TNP Abs was determined on Raji and Ramos B cells at an Ag density of 0.5 mM (medium) TNBS in the presence of 20% serum. All allotypes were tested in duplicates in a 4-fold serial dilution starting at 10 µg/ml. Negative controls are shown as dotted line for TNP unlabeled cells and dashed line represents TNPylated cells in the absence of Abs. Data represent mean ± SEM of n = 3.