MPO and rheumatoid arthritis: The association of a significant fraction of MPO with markedly elevated cell-free nucleosomes in RA serum, which constitute a main component of NETs (Figure 5E), clearly suggests that NETosis is indeed the source of nucleosome material present in RA serum[21].Since there was no significant elevation of these parameters in simultaneously obtained plasma samples that were processed immediately, these data demonstrate a propensity for RA PMN to undergo increased NETosis during coagulation (Figure 5A to E).