Effects of treatment with the Rac1 carboxy-terminal peptide at onset of disease in collagen-induced arthritis. Mice were treated with 2 mg of Ctrl (white bars) or 2 mg of Rac1 (black bars) peptide starting at day 20. After sacrifice, sections from mice paws (n = 8 per group) were stained with hematoxylin and eosin and assessed for (a) cellular infiltration and (b) cartilage erosion. (c) X-rays of hind paws were analyzed for bone damage. (d) Sera from mice that started treatment at day 20 (n = 8) with Ctrl (white bars) or Rac1 (black bars) peptide were collected, and the levels of specific anti-collagen IgG were detected. IgG levels in the sera of Ctrl-treated mice were set to 100%, and the levels obtained in the sera of Rac1-treated mice were then calculated relative to Ctrl. Represented IgG values were calculated within linear regions of the serum dilution curve. All values are presented as mean ± standard error of the mean. *P ≤ 0.05. Ctrl, control.