FIG. 10.

CCR2 requirement to control local growth of ΔyopM Y. pestis CO92 in bubonic plague. Groups of C57BL/6 and CCR2^−/− mice were infected i.d. with 100 to 200 CFU of parent Y. pestis CO92.S6 or 200 to 250 CFU of ΔyopM Y. pestis CO92.S19, and skin and spleens were analyzed for CFU on days 4 and 5 p.i. (D4 and D5, respectively). Because of the large number of mice involved, the infections for the two analysis times were done on different days. To improve the statistical power in the data for the ΔyopM mutant on day 4 p.i., that experiment was repeated and the data for the two experiments were pooled. Each symbol represents one mouse. P-WT, parent strain and WT mice (8 mice in the group); M-WT, ΔyopM mutant and WT mice (14 mice in the group on day 4 p.i. and 8 mice in the group on day 5 p.i.); P-KO, parent strain and CCR2^−/− mice (8 mice in the group); M-KO, ΔyopM mutant and CCR2^−/− mice (14 mice in the group on day 4 p.i. and 8 mice in the group on day 5 p.i.); ×, mouse died prior to analysis. Solid horizontal lines indicate median values of the data sets, and dashed lines show limits of detection (a single colony on one of the duplicate plates). Parentheses indicate data taken from samples with <30 CFU. Significant differences of medians by the Wilcoxon two-sample test are indicated: **, P ≤ 0.01; ***, P ≤ 0.001. On day 5 p.i., the number of P-KO mice that survived to be analyzed was too low for statistical evaluation, and the data for these mice likely underestimate those for the group. One sample of skin from a P-WT mouse on day 5 p.i. was lost, and one sample of spleen from an M-KO mouse on day 4 p.i. could not be enumerated (accounting for one less datum point in those treatment groups).