Figure 1.

C3aR is protective during the second week of C. psittaci lung infection. Thirty-one C3aR^−/− or 34 of the corresponding C57BL/6J WT mice were infected intranasally with 4 × 10⁴ IFU of C. psittaci DC15. Body weight and clinical score were recorded until day 14 p.i. Appearance of mice was assessed using the parameters vocalization, body posture, locomotion, breathing, piloerection, overall attention or curiosity, and secretion (eyes, nose, and anal region). Based on severity, dysfunction in each parameter was rated as 1 or 2 points. The overall physical condition was determined by adding all points resulting in a clinical score of untroubled (0 points) to moribund (≥10 points; in this case, mice were euthanized). Only 19% of infected C3aR^−/− mice survived for 2 weeks. Fourteen mock-treated C3aR^−/− and 12 WT mice did not exhibit any clinical symptoms. After daily monitoring, mice were sacrificed either 9 or 14 d p.i. for further analyses. Survival of mice (A) was statistically analyzed with the Log-rank (Mantel-Cox) test. Body weight (B) was analyzed with 2-way ANOVA and Bonferroni Posttest and clinical score (C) with Mann-Whitney test. Means ± standard errors of the means are depicted. Asterisks indicate significant differences between infected C3aR^−/− and the corresponding infected WT mice (*P ≤ .05; **P ≤ .01; ***P ≤ .001). Abbreviations: ANOVA, analsyis of variance; C3aR, C3a receptor; d p.i., days postinfeciton; IFU, inclusion-forming unit; WT, wild type.