Apoptotic cell injection prevented streptococcal cell wall-induced arthritis. (a) Rats were injected with streptococcal cell wall (SCW) in addition to apoptotic cells (Apo, 2 × 108 cells) or with Apo only and were followed for arthritis occurrence, scored using an articular index for each animal (mean ± standard error of the mean (SEM); n = 3 or 4 rats for each group). P < 0.001, SCW vs. SCW + Apo. (b) Joint swelling and bone destruction were assessed by X-ray exposure in the different groups (representative animals from each group) as well as (c) the joint volume using a plethysmometer, both at day 21 post SCW injection (mean ± SEM; *P < 0.05 vs. PBS, Apo and SCW + Apo). (d) H & E analysis of the joints in rats with the indicated treatments at days 25 and 26 post SCW injection. A representative rat from each group is shown (magnification 20×). Each group contained three to six rats. The experiment was repeated three times with similar results.