Effect of administration of anti-human CD1d mAb on anti-A Ab production in humanized mice. The same dose of PBMCs from each type O human volunteer was intraperitoneally injected into 2 NOD/SCID/γ_c^null mice (20 × 10⁶ cells/mouse). Of these mice, 1 subsequently received anti-human CD1d mAb and the other received isotype-matched irrelevant control Ab at days 7 and 10 after PBMC engrafting. The humanized mice were immunized with human blood group A-RBCs 8 days after PBMC injection. (A) The serum anti-A IgM and IgG levels in the humanized mice were determined using ELISA at 14 and 21 days after engraftment. Each point represents an individual mouse. Each group contained 5 animals. (B) Three weeks after human PBMC engrafting, the humanized mice were sacrificed to determine the proportion of B cells with receptors for group A carbohydrates. Spleen cells were prepared from the humanized mice (n = 4 in each group). The pooled cells were stained with FITC-labeled A-BSA or control FITC-labeled BSA together with PE-conjugated anti-human CD19 mAb. Representative FCM results of group A-BSA–binding spleen cells. We analyzed 50 000 cells per contour plot. The percentages in the figure represent percentages of total CD19⁺ B cells. (C) The frequencies of A-BSA–binding B cells among the total B cell population in mice treated with either anti-human CD1d mAb or isotype-matched control Ab are shown. *P < .05 compared with the data from humanized mice treated with isotype-matched Ab.