Depletion of CD25⁺ cells in animals resistant to arthritis induction leads to a rapid induction of disease. The effect of anti-CD25 administration on the course of PGIA in animals resistant to arthritis induction. Arthritis was induced by 2 injections of PG in DDA on day 0 and day 21. On day 35, animals that had not developed arthritis by then received 2 injections of the anti-CD25 mAb PC61 with a 1-week interval, and mean arthritis scores are shown (+ SEM; N = 9).