Treatment with IL-28A restricts neutrophil infiltration into joint at the early stages of arthritis. (a) Total numbers of neutrophils, macrophages, B cells, CD4⁺ T cells, and γδ T cells in the hind paw arthritic joints of mice on day 4 of treatment with IL-28A or PBS control. The data are mean and SEM derived from five mice treated with IL-28A and five mice treated with PBS in a representative out of three CIA experiments. (b) Histology sections of arthritic joints after 10 d of treatment with IL-28A or PBS control stained for Ly6G. The mean number of positive cells per view over 10 views: 10.2 for mice treated with IL-28A and 37.41 for mice treated with PBS from 2 independent CIA experiments. (c) mRNA levels of neutrophil recruitment mediators in the arthritic joints of mice on day 4 of treatment with IL-28A or PBS control. The data are mean and SEM derived from five mice treated with IL-28A and five mice treated with PBS in a representative out of three CIA experiments. (d) Levels of IFN-γ, IL-1β, IL-6, and CXCL1 in the serum of mice on day 4 of treatment with IL-28A or PBS control. The data are shown as mean with 95% confidence interval using eight mice treated with IL-28A and eight mice treated with PBS from two independent early CIA experiments. Statistical analysis was performed by one-tailed Mann-Whitney U test. *, P < 0.05; **, P < 0.01.