Studies of the anti–platelet factor 4/heparin immune response: adapting the enzyme‐linked immunosorbent spot assay for detection of memory B cells against complex antigens

BACKGROUND: The anti-platelet factor 4 (PF4)/heparin immune response, which underlies heparin-induced thrombocytopenia (HIT), has several atypical features: relatively rapid onset even without previous heparin exposure, lack of immune anamnesis, and transience of antibody production. STUDY DESIGN AND METHODS: We modified the enzyme-linked immunosorbent spot (ELISPOT) assay to investigate for PF4/heparin-specific memory B cells in cardiac …