PTX3 enhances homeostatic IgM and IgG responses to CPS. (A) Flow cytometric analysis of frequency and absolute number of total B220⁺ B cells, B220⁺CD21^hiCD23⁻ MZ B cells, B220⁺CD21⁺CD23⁺ FO B cells, B220⁺CD21⁻CD23⁻CD43⁺ B-1 cells, and B220⁻CD138⁺ PBs/PCs from spleens of WT and Ptx3^−/− mice. (B) ELISA of total IgM and specific IgM to phosphorylcholine (PCh-IgM), CPS serotype 9, CPS serotype 14, and lipoteichoic acid (LTA) from serum of WT and Ptx3^−/− mice. OD was at 450 nm. Data show serum total and antigen-specific Igs from 7–10 mice in each experimental group. (C) qRT-PCR of mRNA for BLIMP-1 (Prdm1) in MZ B cells from WT and Ptx3^−/− mice. Results are normalized to mRNA for HPRT and presented as relative expression (RE) compared with MZ B cells from WT mice. (D) IFA of spleens from WT and Ptx3^−/− mice stained for MMP9 (green), Ly6G (red), and MOMA-1 (blue). Bars, 100 µm. (E) Flow cytometric quantification of NBh cells from spleens of WT and Ptx3^−/− mice. (F) ELISA of total and CPS-reactive IgG in BAL fluids from PTX3-sufficient h1/h1 and h1/h2 patients and PTX3-deficient h2/h2 patients. Data show one representative experiment of at least two with similar results (A and D), summarize one to two experiments with at least eight mice in each experimental group (A and C–E), or show one experiment with samples from at least eight donors in each experimental group (F). Error bars, SEM. *, P < 0.05; **, P < 0.01 (two-tailed Student’s t test).