Background/Purpose: In the context of reduced TCR signaling in the BALB/c ZAP70^W163C mutant (SKG) mouse, development of arthritis, psoriasis-like skin inflammation and ileitis after intra-peritoneal injection of microbial β-glucan (curdlan), is characterized by an overwhelming increase of autoreactive CD4+ T cells in the peripheral organs. Inflammatory disease in SKG mice is observed within 7 days in the intervertebral joint of the upper tail, sacroiliac joints and Achilles tendon. However, curdlan-triggered arthritis in BALB/c mice is mild to absent. The mechanism by which systemic microbial-derived adjuvant promotes T-cell-mediated tissue inflammation in SKG mice but not in BALB/c mice is poorly understood. Here, we studied the role of peripheral Type-1 regulatory T (Tr1) cells in regulating activation and proliferation of autoreactive T cells in the genetically predisposed mice model of Spondyloarthritis (SpA).

Methods: To elucidate the dynamics of post-curdlan CD4+ T cell expansion and regulation, syngeneic luciferase-expressing CD4+ T cells were magnetically sorted from SKG.luc+ mice, adoptively transferred, and tracked in vivo post-curdlan in SKG and BALB/c mice using in vivo bioluminescence imaging. Development of arthritis was monitored in these mice by measuring width of the ankles, wrists and footpads using calipers. Flow cytometry was used to phenotypically characterize effector and regulatory T cell populations. Tr1 cells were generated from naïve CD4+ T cells in vitro using anti-CD3/anti-CD28 and IL-27.

Results: After transfer of SKG.luc+ CD4+ T cells to SKG hosts, bioluminescent images showed CD4+ T cell accumulation in spleen and inguinal lymph nodes 3 days after curdlan, and traffic to joints, tail, and ears at day 7. Subsequently the signal continued to expand as arthritis increased in severity. After transfer of SKG.luc+ CD4+ T cells to BALB/c hosts, signals increased in spleen and inguinal lymph nodes 7 days after curdlan, but subsequently disappeared within 1 week. Furthermore, T cells expanding in SKG mice were significantly more likely to produce IL-17 than in BALB/c mice. In addition, the frequency of CD4+Foxp3+ regulatory T (Treg) cells were significantly higher in SKG mice, both in naïve and after curdlan, compared to BALB/c mice. In contrast, the frequency of CD4+Foxp3-IL-10+IFN-γ+ Tr1 regulatory T cells was significantly lower in SKG than BALB/c mice. Differentiation of naïve SKG or BALB/c CD4+ T cells to Tr1 cells in vitro in the presence of IL-27 was comparable.

Conclusion: These data indicate that autoreactive Th17 cells first expand as a result of autoantigen presented in inguinal lymph nodes in SKG and BALB/c mice. While they are tightly regulated in BALB/c hosts, they expand and rapidly infiltrate joints and skin in SKG hosts, despite increased frequencies of Foxp3+ Treg cells. In contrast, Tr1 cell differentiation is deficient in SKG mice in vivo but can be restored in vitro with addition of IL-27. The data suggest that while IL-27 signaling is intact in ZAP70^W163C mutant T cells, IL-27 production is reduced and contributes to the lack of peripheral tolerance in SKG hosts.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/impaired-control-of-autoreactive-t-cell-expansion-is-coupled-with-type-1-regulatory-t-cell-deficiency-in-balbc-zap70w163c-mutant-mice/