Fig. 1

Role of IL-22 in the acute phase of AIA. a mBSA-immunized mice were challenged i.a. with 30 μg of mBSA or saline. After 3 h, synovial membranes were collected and analyzed for IL-22 mRNA expression by PCR. The gene expression was normalized to GAPDH expression. b The concentrations of IL-22 in the synovial membranes were determined at 1.5, 3 and 7 h after a challenge with either 30 μg of mBSA or saline in mBSA-immunized mice. c Articular hypernociception was evaluated 1–7 h after i.a. injection with either mBSA (30 μg) or saline in mBSA-immunized mice treated with a co-injection of IgG control (α-CTL) or α-IL-22 (5 μg/cavity) antibodies. d Neutrophil recruitment from the articular cavity 7 h after i.a. administration of mBSA (30 μg) or saline and treatment with a co-injection of α-CTL or α-IL-22 antibodies. e and f mBSA-immunized mice were challenged i.a. with either 0.1–3 ng of rmIL-22 or 10 μl of saline. e Articular hypernociception was evaluated over a period of 7 h. f Neutrophil recruitment from the articular cavity 7 h after i.a. injection of either IL-22 (0.1–3 ng per joint) or saline in mBSA-immunized mice. Data are the means ± SEM (n = 5). *P < 0.05, compared with the saline group; ^# P < 0.05, compared with the mBSA plus α-CTL group; and ^& P < 0.05, compared with the IL-22 0.1 and 0.3 ng i.a. groups. AIA antigen-induced arthritis, GAPDH glyceraldehyde 3-phosphate dehydrogenase, i.a. intra-articular, Ig immunoglobulin, IL interleukin, mBSA methylated bovine serum albumin, PCR polymerase chain reaction, rmIL-22 recombinant murine IL-22