In addition, some well-known neutrophil granule-derived proteins (like lactotransferrin, stromelysin-1, elastase, neutrophil gelatinase-associated lipocalin, and MPO) were observed to be significantly present at overabundant levels in RA-SF compared to RA-plasma and HC-plasma (Figure 2C). The gene discussed is MPO; the disease is rheumatoid arthritis.