Fig 2. Infant mice are impaired in macrophage recruitment during colonization.

(A-C) Adult (6 week old) and infant (7d old) mice were inoculated with strain P1121 for the indicated number of days. Nasal lavages were obtained and fixed and stained for flow cytometry to identify macrophages (F4/80+, CD11b-) and neutrophils (CD11b+, Ly6G+). CD11b surface expression was measured on myeloid cells and displayed as median fluorescence intensity. Samples represent at least 10 mice per timepoint. (D) Serum was obtained from adult and infant mice colonized with pneumococci for 21 days, or mock-colonized. Samples were analyzed by ELISA for the presence of antibodies specific to strain P1121. (E) Infant mice of the indicated genotype were colonized at 7d of age. Mice were sacrificed at the indicated timepoints and nasal lavages obtained and plated to measure bacterial load. Data are represented as mean +/- SEM. n.s. = not significant, * = p < 0.05, ** = p < 0.01.