Introduction Impaired removal of apoptotic waste in patients with systemic lupus erythematosus-SLE has been long known as important factor that trigger autoimmune response. Neutrophil extracellular traps could be another source of autoantigens in patients with SLE.

Methods We analysed sera from 84 SEL patients (60 patients had one sample and 24 patients were followed 2 or 3 times) and 50 healthy blood donors. Serum levels of myeloperoxidase, B-cell activating factor-BAFF, cell free DNA, complement components C3 and C3, antibody to dsDNA by CLIFT end ELISA assays, netolitic activity and DNAse I were measured.

Results Patients with SLE had higher cfDNA (1.69±0.23 vs 1.42±031 ng/mL, p=0.0003), MPO (1607±2353 vs 1503±1106, p<0.05) and BAFF levels (160735±2353.23 vs 891.16±184.31, p<0.05). DNAse concentration was also lower in healthy controls (5.84±5.72 vs 9.38±6.97, p<0.05). BAFF showed strong correlation with anti-dsDNA antibodies determined by ELISA method (ρ=0.564, p=0.000), MPO activity (ρ=0.256, p=0.021), DNAse I concentration (ρ=0.27, p=0.012) and cfDNA concentration (ρ=0.262, p=0.014). DNA determined by ELISA test showed correlations with DNAse concentration (ρ=0.249, p=0.022), DNA determined by CLIFT (ρ=0.341, p=0.001) and C3 complement component (ρ=−0.4, p=0.023). MPO activity showed correlations with cfDNA levels (ρ=0.386, p=0.001), DNAse concentration (ρ=0.501, p=0.000), and anti-MPO antibodies (ρ=0.293, p=0.006). Cell free DNA levels additionally correlated with DNAse activity (ρ=0.288, p=0.007) as well with netolytic activity (ρ=0.244, p=0.026). Netolytic activity also correlated with anti-dsDNK antibodies determined by ELISA (ρ=−0.299, p=0.039).

Conclusions Increased NETs` footprints (myeloperoxidase and cfDNA) are present in lupus sera. As probably compensatory mechanism increased DNAse I concentrations also were found in lupus sera. NET burden is followed by production of various antibodies recognising different NET structures.