aCL/β 2 GPI and aPS/PT show synergic thrombogenic effects in suppressing anticoagulant activity of APC and stimulating tissue factor expression and TNF-α secretion by mononuclear cells.

•Among 97 SLE patients enrolled, 27% were positive for APC resistance screening test.•Thrombotic SLE complications were related to aCL/β2GPI and/or aPS/PT, with higher incidence when they were double-positive.•aPLs(+)-IgG patients caused TF expression and TNF-α release from monocyte, and suppressed APC in the APTT-based APC resistance assay.•These effects of aPL IgG were also pronounced when aCL/β2GPI and aPS/PT were double-positive, implying their synergic action.