Fig. 1.

PTIP is required for steady-state and antigen-induced antibody production in vivo. Mice were immunized with (A) TNP-LPS, (B) TNP-Ficoll, or (C) TNP-KLH, and anti-TNP-specific IgM or IgG3 serum levels were measured by ELISA at the indicated days before and after immunization. Data are from four mice of each genotype in A, four mice in B, and seven mice in C, and are plotted as Ig concentration or the absorbance for the serum dilution that gave half optical density (mean ± SEM). Experiments were repeated at least two times. P values at 7 d after immunization are as follows: (A) IgM, *P = 0.03; IgG3, ****P < 0.0001; (B) IgM, *P = 0.02; IgG3, ***P = 0.0003; (C) IgM, ***P = 0.001; IgG3, ****P < 0.0001. (D) Flow cytometric analysis of GC B cells in the spleen at the indicated days after immunization with SRBCs. (E) GC B cell numbers (Top) and frequencies (Bottom) from spleens (as in D) of at least three mice with PBS, five mice at 6 d, and nine mice at 10 d per genotype postimmunization. Data are presented as mean ± SEM. (Top) Day 6, *P = 0.02; day 10, **P = 0.003; PBS vs. day 6 in WT, **P = 0.001. (Bottom) Day 6, ****P < 0.0001; day 10, **P = 0.002; PBS vs. day 6 in WT, ****P < 0.0001. (F) Flow cytometric analyses of IgG1⁺ frequencies among GC B cells as in D. Data are presented as mean ± SEM. Day 6, ***P = 0.0005; day 10, ****P < 0.0001; PBS vs. day 6 in WT, ****P < 0.0001. (G) ELISA analysis of total Ig levels from sera of unimmunized mice. Data are from at least six mice of each genotype and are presented as mean ± SEM. IgG1, *P = 0.015; IgG2a, ***P = 0.001; IgG2b, **P = 0.005; IgG3, **P = 0.004; IgM, **P = 0.002; anti-PC IgM, ***P = 0.0006. (H) ELISA analysis of total Ig levels from sera of unimmunized mice. Data are from at least six mice of each genotype and are presented as mean ± SEM. IgG1, *P = 0.046; others not significant (ns). Statistics were generated by using a two-tailed unpaired t test with Welch’s correction.