FIG. 1.

Increased susceptibility of Csf1^op/Csf1^op mice to L. monocytogenes infection. Mice (+/Csf1^op and Csf1^op/Csf1^op) were infected with 10⁴ L. monocytogenes i.v. Groups of infected mice were sacrificed at 1, 24, 48, and 72 h p.i., and the numbers of CFU of L. monocytogenes recovered from spleen (a) and liver (b) were determined by plating serial dilutions of tissue homogenate on tryptic soy agar plates. In another set of experiments, either (c) mice were infected with 10³ L. monocytogenes cells i.v. or (d) weight-matched (18- to 20-g) mice were challenged with 10⁴ L. monocytogenes cells i.v. and the CFU from liver and spleen were enumerated. Each data point represents the mean and standard error of the mean of 8 mice in panels a and b and of 5 mice in panels c and d. The experiment was repeated two times with similar results (∗, P < 0.001; ∗∗, P < 0.05; Mann-Whitney U test).