Objectives: Increased percentages of neutrophils expressing proteinase 3 on their membrane (mPR3) have been reported in ANCA-associated vasculitis (AAV) and suggested to be involved in its immunopathogenesis. In most studies, neutrophils (PMN) were analysed for mPR3 expression without priming with TNF-alpha, implicating that mPR3 expression on neutrophils is dependent on other priming events, i.e. isolation procedures. These priming events can be variable. Therefore, we analyzed mPR3 expression on PMN before and after priming with TNF-alpha in order to assess whether standardized assessment of mPR3 expression requires priming. Using PMN before and after priming with TNF-alpha, we assessed percentages of mPR3+ PMN in patients with AAV and in disease- and healthy controls.
Methods: PMN from patients with PR3-ANCA- and MPO-ANCA-AV, systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA), and from healthy controls were analyzed before and after priming with TNF-alpha for mPR3 expression.
Results: 42% of all individuals analysed showed minimal expression for mPR3 on all PMN before priming with TNF-alpha, whereas after priming a clear mPR3+ subset was observed next to mPR3- PMN, corresponding with bimodal mPR3 expression. In patients with PR3-ANCA- or MPO-ANCA-AV, percentages of mPR3+ PMN after priming with TNF-alpha were significantly increased (p < 0.01 and p < 0.05, respectively) compared to healthy controls. Percentages of mPR3+ PMN were also increased in patients with SLE (p < 0.01), but not in RA.
Conclusion:Standardized assessment of proteinase 3 on the membrane of PMN requires priming with TNF-alpha. Percentages of mPR3+ PMN are increased in AAV and SLE, but not in RA.
- Wegener's granulomatosis
- chronic inflammation
- proteinase 3
- systemic lupus erythematosus