PY GAN1,2, A CHAN1, J DICK1,3, MA ALIKHAN1, JD OOI1, AR KITCHING1,3, SR HOLDSWORTH1,2,3
1Department of Medicine, Centre for Inﬂammatory Diseases, Monash University, Clayton, Victoria; 2Department of Immunology, Monash Health, Monash Medical Centre, Clayton, Victoria; 3Medical Centre, Clayton, Victoria
Department of Nephrology, Monash Health, Monash
Aim: To test the hypothesis that biological neutralization of the dominant T helper (TH) cell subset inducing cytokine attenuates anti-MPO GN.
Background: Both CD4+ TH17 and TH1 cells, have been demonstrated to be pathogenic in anti-MPO GN. Definition of the dominant TH subset would allow targeted biological treatment.
Methods: Anti-MPO autoimmunity was induced by MPO immunisation and GN triggered using anti-GBM Ig. TH subsets in anti-MPO GN was defined by their cytokine profile in draining lymph nodes (dLN) and glomerular effector responses. TH subsets was assessed early after induction of anti-MPO GN on day 20 (d20) and when disease was fully established (d32).
Results: In WT mice, anti-MPO GN progressively intensifies from d20 to d32 with increasing frequency of segmental necrosis (10±1vs17±2%, P<0.01) and albuminuria (1.22±0.2vs2.0±0.2mg/24hr, P<0.05). Analysis of TH cytokines in dLN showed key TH17 cytokines, IL-17A (2.8±0.1vs1.6±0.3ng/ml, P<0.05) and IL-6 were maximal at d20 and subsides by d32 while TH1 dominant cytokines, IFNγ (19.9±8.1vs52.9±12.3pg/ml, P<0.05) and TNF-α were maximum at d32. Gene analysis of isolated kidney CD4+ T cells demonstrated that expression of TH17 genes (IL-17A, CCR6, TGF-β) are more upregulated early while upregulation of TH1 genes (IFNγ, CXCR3, STAT4) increases by d32. This suggests TH17 dominates GN early and TH1 late.
Treatment with monoclonal antibodies (mAb) to the TH17 inducing cytokine, IL-23p19, attenuated GN (albuminuria; 105.3±28.2vsIgG2b controls; 325.4±60.5µg/24hr, P<0.01) on d20 but not on d32. Whereas mAb to TH1 inducing cytokine, IL-12p35, was protective at d32 (albuminuria, 788.2±323.3vs IgG2a controls; 1797±229.9µg/24hr, P<0.05).
Conclusion: In anti-MPO GN, TH subset dominance is biphasic, TH17 early then TH1 late. Anti-cytokine biological treatment is effective only when it targets the dominant TH cytokines inducing anti-MPO GN.