Increased susceptibility to S. pneumoniae infection in Stat1−/− mice is intrinsic to the loss of STAT1 in MZ B cells. (A) MZ B cells sorted from WT and Stat1−/− mice were intravenously transferred into RBP-J CKO mice. 1 d later, chimeric mice were primed with 105 CFU HK-S. pneumoniae for 1 d before being challenged with a lethal dose of 103 live S. pneumoniae. Survival curves are shown. dpi, days postinfection (n = 5–6). Results represent three experiments. (B) Same as in A, except bacterial loads in the blood were measured (n = 3–6). # mice died. Results represent three experiments. (C and D) Same as in A, except serum total IgM and PC-specific IgM were measured by ELISA at the indicated times (n = 3–6). Results represent two experiments. All values are shown as the means ± SD. *, P < 0.05, Log-rank test (A) or Student’s t test (B–D).
