S100A9 and Arthritis: It is worth mentioning that besides the skin and paws, all other tissues and joints analyzed, including the gut and the highly “arthritis-sensitive” joints, such as the spine, sacroiliac, and hip joints, were S100A9 negative and did not show noteworthy morphologic alterations (see http://zmbe.uni-muenster.de/vwixler/retser.zip).