Reactivity of patients' anti-FIX IgGs against FX/FIX chimeras containing Gla and/or EGF-like domains of FIX.

To distinguish the reactivity of patients' IgGs toward Gla-containing domain and EGF-like domains of FIX, medium from cells expressing chimeras FX/FIX-Gla, FX/FIX-EGF1, FX/FIX-Gla-EGF1, and FX/FIX-EGF1-EGF2 was added to microtiter plates coated with polyclonal anti-FX antibody. The response of patients' anti-FIX IgG against the chimeras was investigated in the presence of Ca⁺⁺ as described in “Patients, materials, and methods.” Data represent the mean values from 3 to 6 experiments (± SD).