Impaired homing of Rap1b-deficient B cells to the lymph nodes in vivo and slightly impaired immune response to TI-specific antigens in Rap1b-deficient mice. (A) Homing of wild-type and Rap1b-deficient B cells to lymph nodes in vivo. Purified splenic B cells from wild-type (+/+) and Rap1b-deficient (−/−) mice were labeled with PKH26 and CFSE, respectively. Equal numbers of labeled wild-type and Rap1b-deficient B cells were mixed and injected into the tail veins of C57BL/6 wild-type mice. After 1 hour, mononuclear cells from peripheral blood (PB), spleen (SPL), BM, and lymph nodes, including inguinal (ILN), axillary (ALN), and mesenteric (MLN), were analyzed by flow cytometry. Data shown are representative of 3 independent experiments. Each experiment contains 2 recipients. (B) Immune response to TI-specific antigens in wild-type and Rap1b-deficient mice. Wild-type (n = 6) and Rap1b-deficient (n = 6) mice were immunized intraperitoneally with the TI antigen, TNP-Ficoll. 7 days after immunization, the titers of TNP-specific IgM in sera were determined by ELISA. Mean values are indicated with black bars. (C) Immune response to TD-specific antigens in wild-type and Rap1b-deficient mice. Wild-type (n = 7) and Rap1b-deficient (n = 7) mice were immunized intraperitoneally with TD antigen, NP-CGG. Fourteen days after immunization, the titers of NP-specific IgG1 in sera were determined by ELISA. Mean values are indicated with black bars.