Demonstration that IL-4 and PNM induce Ag-specific Tregs that express mRNA for the IL-5Rα and that IL-5 can suppress induction of EAN. (A) IL-5 receptor α mRNA (Il-5rα) was induced in CD4⁺CD25⁺ Tregs from normal Lewis rats that were cultured with (■) and without (□) PNM, the Ag used to induce EAN and IL-4. Culture with PNM and IL-2 did not induce Il-5rα. This is similar to induction of Il-5rα in Tregs by culture with alloantigen and IL-4 but not with IL-2.³  (B) Human CD4⁺CD25⁺ T cells cultured with IL-4 and alloantigen also expressed Il-5rα but not if cultured with IL-2. This confirmed that Il-5rα can be induced in human Tregs activated by IL-4. (C) Compared with controls with EAN (○), IL-5 therapy reduced the severity of EAN induced in Lewis rats by immunization with PNM in CFA.^18,19  Top panel shows treatment with IL-5, either 5000 U/d (●) or 500 U/d (gray circle) from 9 to 18 days after immunization, delayed onset of EAN (n = 6 per group); 5000 U/d fully suppressed EAN, with P < .001 on days 14-21, P < .03 on days 13 and 21. This dose was used in all subsequent experiments. With 500 U of IL-5, clinical severity was less at days 13-16 and day 18 (P < .05). Clinical disease was scored as 1+ for limp tail, 2+ for hind leg weakness, 3+ for paraplegia, and 4+ for quadriplegia.^18,19  Bottom panel shows weight loss was also reduced in IL-5–treated animals. There is early weight loss after immunization, which continues in controls. Weight loss is arrested with treatment with 5000 U of IL-5 and partially reduced with treatment with 500 U of IL-5.