Anti-proteinase 3 antibodies (c-ANCA) prime CD14-dependent leukocyte activation

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Abstract
In Wegener’s granulomatosis (WG), a pathogenetic role has been proposed for circulating anti-neutrophil-cytoplasmic antibodies (ANCA) targeting proteinase 3 (PR3). Disease activation in WG appears to be triggered by bacterial infections. In the present study, we characterized the effect of anti-PR3 antibodies on in vitro activation of isolated monocytes and neutrophils by the bacterial cell-wall components lipopolysaccharide (LPS) and lipoteichoic acid (LTA). Although sole incubation of monocytes and neutrophils with monoclonal anti-PR3 antibodies induced the release of minor quantities of the chemokine interleukin-8 (IL-8), preincubation with anti-PR3 antibodies, but not with isotype-matched control immunogloblin G (IgG), resulted in a markedly enhanced IL-8 liberation upon LPS challenge. The priming response was evident after 2 h of preincubation with anti-PR3 and peaked after 6 h. The anti-PR3-related priming was also observed for tumor necrosis factor α (TNF-α) and IL-6 synthesis. Comparable priming occurred when leukocytes were preincubated with ANCA-IgG derived from WG serum but not with normal IgG. The priming effect of the anti-PR3 antibody pretreatment was reproduced for LTA challenge of monocytes and neutrophils but not for leukocyte stimulation with TNF-α. Flow cytometric analysis revealed an increase in monocyte and neutrophil membrane CD14 expression during the anti-PR3 priming. We conclude that cytoplasmic ANCA specifically prime CD14-dependent monocytes and neutrophils for activation. The resulting enhanced responsiveness to bacterial pathogens may contribute to the development and maintenance of inflammatory lesions during active WG.
Funding Information
  • Deutsche Forschungsgemeinschaft (GR 534, SFB 547/B8)