Clinical evaluation of arthritis and flow-cytometry analyses of properdin-deficient and wild-type synovial neutrophils. (A) Properdin-deficient (KO, n = 15) and wild-type (WT, n = 15) mice were intraperitoneally injected with a collagen antibodies cocktail followed by administration of LPS at Day 3 (arrow). Photos show the hind-paw swelling of WT and KO mice at Day 10 of arthritis. Clinical score was calculated for each time point by using the semiquantitative grading system. Data are expressed as the mean ± SD. Significant differences of *P < 0.05; **P < 0.01; and ***P < 0.001 between KO and WT groups are indicated, Mann-Whitney U test. Line segment with *P < 0.05 shows the statistical significance between WT and KO line curves; Mann-Whitney U test. (B) The frequencies of Ly6G+CD11b+ neutrophils were less in synovial fluid of properdin-deficient than in wild-type mice at Day 10 of arthritis. The data are representative of three separate experiments and show the analyses of the synovial cell pool from five mice/group. (C) Lower numbers of Ly6G+C5aR+-bearing cells and (D) decreased amounts of C5a were found in synovial fluid of properdin-deficient mice with arthritis in comparison with wild-type CAIA mice. Data are expressed as the mean ± SD of two experiments involving five mice/group. *P < 0.05; **P < 0.01; and ***P < 0.001; Student t test. (E) RANKL was expressed on wild-type synovial CAIA neutrophils but not on properdin-deficient arthritic cells. The data are representative of three separate experiments and show the analyses of the synovial cell pool from five mice/group. (F) IL-17 production in synovial fluid of wild-type mice was significantly higher than that of properdin-deficient mice at Day 10 of disease. Data represent the mean ± SD of two experiments involving five mice/group. *P < 0.05; **P < 0.01; Student t test.
Dimitrova et al. Arthritis Research & Therapy 2012 14:R173 doi:10.1186/ar3926