Complement testing

The levels and function of complement proteins were determined as reported previously 17. Briefly, C1INH, C4 and C3 serum levels were measured by nephelometry (Siemens, Marburg, Germany). C1INH functionality in plasma was quantified by the Berichrom^® chromogenic assay (Siemens Healthcare Diagnostics, Eschborn, Germany) and serum levels of C1q were assessed by radial immunodiffusion (Binarid Radial Immunodiffusion kit; The Binding Site, Birmingham, UK). Anti‐C1q antibodies were determined in all samples with the human complement C1q NL Bindarid kit (The Binding Site).