IdeS cures mice from lethal IgG-induced thrombocytopenia.

(A) Fourteen BALB/C mice were injected i.p. with a lethal dose of purified polyclonal rabbit IgG antibodies (1 mg IgG/ mouse, diluted in 0.25 ml PBS) raised against mouse platelets. Thirty minutes later, seven mice were treated i.p. with 0.5 mg IdeS in 0.25 ml PBS and seven with 0.25 ml PBS alone. In another experiment, twelve Balb/c mice were injected i.p. with the lethal dose of IgG. After thirty minutes, six mice were given 0.5 mg IdeS in 0.25 ml PBS, and six were given 0.25 ml PBS alone. In this case, the injections were given i.v. The thirteen IdeS treated mice (○) all survived, whereas the thirteen PBS treated mice (▪) all died within 24 hours. (B) Blood samples from the twelve mice injected with the lethal dose of purified rabbit IgG and treated i.v. with IdeS or PBS alone (six mice in each group), were analyzed using flow cytometry of the platelet population. Samples from two representative animals, one injected with IdeS and one with PBS, are shown. (C) The number of platelets in the blood samples from the twelve animals treated i.v. was counted manually; six treated with IdeS (○) and six with PBS (▪). Error bars indicate ±SEM.