Redundant tolerance mechanisms prevent autoimmune liver inflammation in mice

Background:

The role of Foxp3+ regulatory T cells (Tregs) in autoimmune liver inflammation is still being discussed. Whereas some reports suggested that autoimmune liver inflammation is linked to Treg dysfunction, others could not confirm this observation.

Aims:

Here, we investigated the consequences of Treg or IL-10 impairment for the development of autoimmune hepatitis. We used a mouse model that is characterised both by ectopic expression of the prototypical autoantigen myelin basic protein (MBP) in the liver and by the presence of autoreactive MBP-specific T cells due to a transgenic T cell receptor.

Methods:

The functionality of T effector cells in (CRP-MBP x tg4) mice was confirmed in vivo and in vitro. Treg impairment in these mice was induced either by application of a Treg depleting anti-CD25 antibody, or by crossing with hCD2-ΔkTβRII mice. In these mice, T cells feature a dominant-negative TGFβ receptor that prevents peripheral Treg induction.

Moreover, the role of IL-10 for the maintenance of hepatic tolerance was assessed in (CRP-MBP x tg4 x dnIL10R) mice, in which T cells are insensitive to IL-10. Alternatively, anti-IL10 receptor anti-body was administered to (CRP-MBP x tg4) mice.

Results:

(CRP-MBP x tg4) mice were completely resistant to the induction of autoimmune inflammation in liver and CNS. MBP-specific effector cells of (CRP-MBP x tg4) mice were functional, as indicated by their capability to secrete IL-17 (371.0 pg/ml vs. 191.0 pg/ml of wildtype tg4 cells) and IFNγ (339.8 pg/ml vs. 429.2 pg/ml of wildtype tg4 cells). Moreover, (CRP-MBP x tg4) mice manifested elevated Treg numbers in spleen (10.5% CD4+Foxp3+ vs. 8.12% of wildtype tg4 cells) and liver (12.67% CD4+Foxp3+ vs. 6.33% of wildtype tg4 cells). However, neither Treg depletion with anti-CD25 antibody in (CRP-MBP x tg4) mice nor Treg impairment in (CRP-MBP x tg4 x hCD2-ΔkTβRII) precipitated autoimmune inflammation of liver or CNS.

Upon adoptive transfer into CRP-MBP mice, MBP-specific CD4 T cells differentiated into CD49b+Lag3+ Tr1-like cells. However; impairment of IL-10 signalling did not lead to autoimmune inflammation in liver or CNS. Even simultaneous abrogation of both Treg and IL-10 signalling in (CRP-MBP x tg4 x hCD2-ΔkTβRII) mice treated with anti-IL10R antibody or (CRP-MBP x tg4 x dnIL10R) mice treated with anti-CD25 antibody did not result in autoimmune inflammation in liver or CNS.

Conclusion:

Our findings show that neither Treg impairment nor the abrogation of IL-10 signalling alone or in combination do result in the development of autoimmune hepatitis. Thus, redundant, but yet undefined tolerance mechanisms safeguard the maintenance of hepatic tolerance.

Corresponding author: Leypoldt, Lisa

E-Mail: [e-mail]