CR2Fc treatment does not induce an anti-EL4 IgM or IgG response. IgM (A), IgG (B), or IgG2a (C) was measured in the serum at day 0 and on day 19 after tumor challenge by a flow cytometry-based method. No significant differences were detected in IgM response between groups (A). Increased anti-EL4 IgG was seen in mAb and mAb + CR2Fc-treated mice (B), but only IgG2a isotype was elevated (C), which is the isotype of the treatment mAb.