cDKO mice show a reduced immune response to TNP-Ficoll. WT, WKO, and cDKO mice were injected IV with 2.5 μg of TNP-Ficoll. (A) Uptake of TNP-Ficoll in the spleen 30 minutes and 3 hours after injection. Spleen sections were labeled to detect TNP-Ficoll and MOMA⁺ metallophilic macrophages to define the MZ. Note the marked reduction of TNP in the MZ at 30 minutes (top panel) and in the follicle at 3 hours (bottom panel) in cDKO mice compared with WT mice. Original magnification was 10×. (B) MZ B cells were labeled with anti-TNP Abs and analyzed by flow cytometry. (C) Anti-TNP IgM and IgG3 Ab titers were determined at day 7 after immunization by ELISA. Test samples were corrected for background binding. Each group represents 6 WT, 3 WKO, and 4 cDKO mice. Black bar represents the mean value for the group. Non-B indicates lymphocytes negative for CD21 and IgM; and RP, red pulp. *P < .05 compared with WT.