(Left) Swelling of the left hind paws (mean ± standard error of the mean) in different phases of adjuvant arthritis (AA). Swelling usually starts around day 10 after immunization, followed by the development of accelerating arthritis (day 17) and chronic arthritis (day 23). (Right) Distribution of TUNEL-positive cells (red, indicated by arrows) in joints of AA rats on day 11 (a and c) and on day 23 (b and d). Very few TUNEL-positive cells were detected in normal rats or during the onset of arthritis, whereas the number of TUNEL-positive cells were significantly increased in the synovium (and also in cartilage) of rats with chronic AA. TUNEL method counterstrained with Mayer's hemalum. Original magnification 250x.