This study characterized the human apolipoprotein H [APOH; b2-glycopro-tein I (b2GPI)] promoter and its variants byin vitro functional experiments and investigated their relationship with human plasmab2GPI levels. We examined the individual effects of 12 APOHpromoter single nucleotide polymorphisms in the 5¢ flanking region ofAPOH( kb) on luciferase activity in COS-1 cells and HepG2 cells and their impact on plasma.