Longevity & AgingHow Rogue Antibodies Against Platelet Factor 4 Trigger Dangerous Clotting Disorders
A review in the New England Journal of Medicine brings together a family of rare but dangerous conditions caused by platelet-activating antibodies against platelet factor 4 (PF4). These include heparin-induced thrombocytopenia (HIT), its autoimmune and spontaneous variants, vaccine-induced immune thrombocytopenia and thrombosis (VITT), and VITT-like illness after natural viral infection, especially adenovirus. A specific genetic background (IGLV3-21*02/*03) and a somatic mutation (K31E) can redirect antibodies from adenovirus protein VII toward PF4. Rare monoclonal anti-PF4 antibodies can cause chronic clotting. The authors emphasize that diagnosis depends on distinct assays for HIT and VITT antibodies. Beyond anticoagulation, treatments that block FcγIIa receptor-mediated platelet activation, such as high-dose immune globulin for acute disease and Bruton's tyrosine kinase inhibitors for chronic disease, may be needed when antibodies activate platelets without heparin.
