An antibody that blows up platelets

Immunologic thrombocytopenia, a frequent complication of HIV-1 infection, is associated with circulating immune complexes that contain platelet membrane components and anti-platelet membrane GPIIIa49-66 IgG antibodies. In September 7 Cell, Michael Nardi and colleagues from New York University School of Medicine show that anti-platelet GPIIIa49-66 IgG alone can causes platelet fragmentation independent of complement, via the induction of reactive oxygen species.

Nardi et al. found that purified anti-GPIIIa49-66 causes in vivo platelet fragmentation in wild-type and complement-deficient mice. In addition, in vitro experiments with inhibitors of reactive oxygen species, and in vivo studies carried out with p47phox-deficient mice showed that the complement-independent platelet lysis is caused by the antibody-induced generation of H₂0₂ (Cell 2001, 106:551-561).

"This was an unexpected finding because antibodies had never been shown to act in this fashion," said Simon Karpatkin the senior author of the paper. "We believe that this discovery...