OBJECTIVES: A decreased ability to degrade neutrophil extracellular traps (NETs) 
is seen in a subgroup of patients with systemic lupus erythematosus (SLE) and 
correlates with the presence of autoantibodies. Antiphospholipid syndrome (APS) 
can develop secondary to SLE or as a primary disease. In the current study we 
investigated the ability of sera from patients with APS to degrade NETs. The 
presence of antibodies against NETs and neutrophil remnants were also determined 
in the same patients.
METHODS: In the study, 106 patients with APS (73 primary and 33 secondary), 76 
patients with systemic sclerosis (SSc) and 77 healthy donors as control samples 
were included. NETs generated from neutrophils isolated from healthy volunteers 
were incubated with patient sera, followed by measurement of degraded NETs or 
deposited IgG.
RESULTS: Sera of APS patients had a decreased ability to degrade NETs compared 
to healthy controls, with no difference between primary and secondary APS. Sera 
from SSc patients did not differ significantly from healthy controls in the 
ability to degrade NETs. A decreased degradation of NETs correlated weakly to 
increased levels of antibodies against NETs/neutrophil remnants in patients with 
primary APS, but stronger in patients with secondary APS.
CONCLUSIONS: The ability to degrade NETs is decreased in a subgroup of patients 
with APS and is associated with antibodies against NETs and specific clinical 
manifestations in those patients.