Cdc42 is essential for antibody responses to NP-KLH. (A) Serum from WT and Cdc42 KO mice was collected and Ig (IgM, IgG1, IgG2b, and IgG2c) levels were measured by ELISA. Data are representative of more than two independent experiments with at least three mice in each group. (B and C) WT and CDc42 KO mice were immunized with NP-KLH in alum. NP₂₃-specific IgM (B) or IgG1, IgG2b, IgG2c, and IgG3 (C) titers were measured by ELISA. Graphs represent NP-specific titers in WT (black dots) or Cdc42-KO (clear dots). (D) ELISA analysis showing affinity maturation of total IgG and IgG1, IgG2b, or IgG2c isoforms in response to NP-KLH in WT and Cdc42 KO mice, expressed as the ratio of NP3 to NP23. Data are representative of 2 independent experiments with at least 3 animals in each group. Mean and SEM. Student’s t test. *, P < 0.05; **, P < 0.01; ***, P < 0.0001; ****, P < 0.00001.