In vitro cytokine production and proliferation of T cells from patients with anti‐proteinase 3‐ and antimyeloperoxidase‐associated vasculitis,in response to proteinase 3 and myeloperoxidase

Objective

To investigate in vitro proliferative responses of CD4+ T cells and generation of specific cytokines induced by stimulation of peripheral blood mononuclear cells (PBMCs) from patients with antineutrophil cytoplasmic antibody (ANCA)‐associated vasculitis with the autoantigens proteinase 3 (PR3) and myeloperoxidase (MPO).

Methods

PBMCs from vasculitis patients with PR3 ANCA or MPO ANCA and from healthy controls were stimulated for 7 days with PR3, MPO, or control stimuli. Proliferation of CD4+ T cells was assessed by flow cytometry, using the proliferation marker Ki‐67. Levels of the pro‐proliferative cytokines interleukin‐2 (IL‐2) and IL‐6 and of the Th1 and Th2 cytokines interferon‐γ (IFNγ) and IL‐10 in culture supernatants were determined.

Results

PR3 and MPO induced proliferative responses in CD4+ T cells from individual patients with ANCA‐associated vasculitides and healthy controls in vitro. Neither PR3 nor MPO elicited significant IL‐2 production. Levels of IL‐6 were highest after stimulation with PR3 but low after stimulation with MPO, independent of study group. Stimulation with PR3, and to a lesser extent with MPO, induced a Th2 cytokine milieu, characterized by high production of IL‐6 and IL‐10 and low production of IFNγ in patients and controls.

Conclusion

PR3 and MPO promote proliferation of CD4+ T cells from patients with ANCA‐associated vasculitides, but also cross‐stimulate T cells from healthy individuals. Strong IL‐10 production elicited by PR3 in vitro may act as an inhibitory signal for T cell proliferation and may have an important immunoregulatory function in vivo.