FIGURE 10.

CD138⁺ cells from NP-exposed aged hosts are not sufficient for protection of naive mice against pulmonary challenge. (A) Young (2-mo-old) and old (20- to 22-mo-old) C57BL/6 male mice were NP exposed to S. pneumoniae TIGR4, the bone marrow was harvested, and the percentage od CD138⁺ cells was measured by flow cytometry. Data shown are pooled from two experiments with a total of six mice per group. Asterisks indicate p < 0.05. (B) Three weeks after NP exposure, bone marrow cells from young and old mice enriched for CD138 were transferred into mice pretreated with 5-fluorouracil. Mice were then challenged i.t. with 2.5 × 10 CFU of S. pneumoniae TIGR4. Survival was assessed at the indicated time points, and fractions denote survivors over the total number of mice. Asterisks indicate a statistical significance (p < 0.05) by the log-rank (Mantel–Cox) test. Data were pooled from three independent experiments.