Figure 2. MDL-1 activation enhances autoimmune arthritis. (A) Treatment with anti–MDL-1 agonist mAb exacerbates CAIA. B10RIII mice (n = 5/group) were given arthrogen to induce arthritis. Mice treated with anti–MDL-1 mAb (clone DX163) at the time of arthrogen treatment showed disease exacerbation compared with isotype controls. Maximum clinical score of individual mice from two separate anti–MDL-1 treatment studies is shown on the right. Results are representative of at least four experiments. (B) Anti–MDL-1 treatment increases the absolute number of bone marrow granulocytes and monocytes. Each data point is FACS analysis of cells extracted from two tibias. (C) Peripheral blood peroxidase-positive neutrophils and macrophages are elevated in anti–MDL-1 treated mice, as shown by ADVIA analysis. The studies in B and C were performed twice. (D) Representative H&E-stained micrographs of metatarsal-phalange joints from the study shown in A. Bars: (top left, bottom left, and top right) 200 µm; (bottom right) 60 µm. The anti–MDL-1 agonist treatment group showed intense neutrophil and macrophage infiltration, as well as pannus tissue formation with extensive bone erosion. (E) Histopathology was performed in a masked fashion. Leukocyte infiltration and percentage of PMN infiltration were determined in the synovium and joint space. Percent PMNs: 1 = <20%, 2 = 20–40%, 3 = 40–60%, and 4 = >60%. Pannus tissue formation, cartilage destruction, and cortical bone erosions were assessed as described in the Materials and methods section. The severity was graded on a scale of 0–4. Comparisons between anti–MDL-1 and isotype control were determined using the Mann Whitney U test. * indicates P < 0.05 and is considered statistically significant. (F) Depletion of granulocytes/monocytes reduced anti–MDL-1–driven CAIA. Date shown are summary of two separate experiments (n = 10 per treatment group). Disease was induced as in A with additional groups that were pretreated on day −1 with anti-GR1 mAb (clone RB6-8C5, rIgG2a isotype) that depletes Ly6G+ and a subset of Ly6C+ cells. Disease was induced on day 0 and mice were given anti–MDL-1 mAb (clone DX163) or an IgG1 isotype control. Depletion of GR1+ populations was confirmed by flow cytometry (Fig. S4).
Figure 2.

MDL-1 activation enhances autoimmune arthritis. (A) Treatment with anti–MDL-1 agonist mAb exacerbates CAIA. B10RIII mice (n = 5/group) were given arthrogen to induce arthritis. Mice treated with anti–MDL-1 mAb (clone DX163) at the time of arthrogen treatment showed disease exacerbation compared with isotype controls. Maximum clinical score of individual mice from two separate anti–MDL-1 treatment studies is shown on the right. Results are representative of at least four experiments. (B) Anti–MDL-1 treatment increases the absolute number of bone marrow granulocytes and monocytes. Each data point is FACS analysis of cells extracted from two tibias. (C) Peripheral blood peroxidase-positive neutrophils and macrophages are elevated in anti–MDL-1 treated mice, as shown by ADVIA analysis. The studies in B and C were performed twice. (D) Representative H&E-stained micrographs of metatarsal-phalange joints from the study shown in A. Bars: (top left, bottom left, and top right) 200 µm; (bottom right) 60 µm. The anti–MDL-1 agonist treatment group showed intense neutrophil and macrophage infiltration, as well as pannus tissue formation with extensive bone erosion. (E) Histopathology was performed in a masked fashion. Leukocyte infiltration and percentage of PMN infiltration were determined in the synovium and joint space. Percent PMNs: 1 = <20%, 2 = 20–40%, 3 = 40–60%, and 4 = >60%. Pannus tissue formation, cartilage destruction, and cortical bone erosions were assessed as described in the Materials and methods section. The severity was graded on a scale of 0–4. Comparisons between anti–MDL-1 and isotype control were determined using the Mann Whitney U test. * indicates P < 0.05 and is considered statistically significant. (F) Depletion of granulocytes/monocytes reduced anti–MDL-1–driven CAIA. Date shown are summary of two separate experiments (n = 10 per treatment group). Disease was induced as in A with additional groups that were pretreated on day −1 with anti-GR1 mAb (clone RB6-8C5, rIgG2a isotype) that depletes Ly6G+ and a subset of Ly6C+ cells. Disease was induced on day 0 and mice were given anti–MDL-1 mAb (clone DX163) or an IgG1 isotype control. Depletion of GR1+ populations was confirmed by flow cytometry (Fig. S4).

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