Wegener's granulomatosis: antiproteinase 3 antibodies induce monocyte cytokine and prostanoid release-role of autocrine cell activation

Antineutrophil cytoplasmic antibodies (ANCA) targeting proteinase 3 [PR3; cytoplasmic ANCA (c-ANCA)], a leukocyte serine protease, are highly specific for Wegener's Granulomatosis (WG). A pathogenetic role for c-ANCA has been proposed as a result of their ability of activating neutrophils, whereas their interaction with monocytes is less well characterized. We investigated the influence of monoclonal anti-PR3 antibodies (anti-PR3) and c-ANCA from WG sera on monocyte cytokine and prostanoid release. We found that PR3 was expressed on the surface of isolated monocytes. Anti-PR3 challenge provoked a pronounced release of cytokines with early appearance of tumor necrosis factor alpha (TNF-alpha) and interleukin (IL)-1beta and delayed release of IL-6, IL-8, and thromboxane A2 (TxA2). The secretory response was reproduced by c-ANCA but not by human and murine control IgG and anti-CD14 antibodies. Because F(ab)2 fragments of anti-PR3 were ineffective, coligation of Fc gamma receptors (FcgammaR) was apparently mandatory for monocyte activation. Using soluble receptors for TNF-alpha and IL-1beta and a Tx receptor antagonist, we noted that the "early" cytokines functioned as inducers of TxA2, which then activated IL-8 release. In contrast, IL-6 formation was an independent event. We concluded that anti-PR3 antibodies are potent inducers of monocyte cytokine and prostanoid release, and TNF-alpha, IL-1beta, and TxA2 function as facilitators of the secretory response. These mechanisms may contribute to inflammatory tissue injury in WG.