Background/Purpose: Our previous study demonstrated that T cells specific RORγt transgenic-mice under human CD2 promoter (RORγt-Tg mice) developed severe spontaneous sialadenitis like Sjögren’s syndrome (SS) in which RORγt overexpressed CD4⁺T cells and reduced regulatory T cells (Tregs) contributed to the pathogenesis. The purpose of this study was to clarify the effectiveness and its mechanisms of RORγt antagonist (A213) for sialadenitis like SS in RORγt-Tg mice.

Methods: 1. In vivo experiments.
 6 weeks aged RORγt-Tg mice were administered orally 300 mg/kg of A213 or phosphate buffered saline (PBS) every three days for two weeks. We compared 1) saliva volume, 2) histopathology of salivary glands, 3) proportion of CD4⁺CD25⁺T cells in spleen and cervical lymph nodes (cLNs), 4) percentages of CD4⁺CD25⁺Foxp3⁺ and CD4⁺CD25⁺Foxp3^–cells in CD4⁺T cells of cLNs, and 5) the protein expression levels of CD69 on CD4⁺CD25⁺Foxp3⁺ and CD4⁺CD25⁺Foxp3^–cells, between A213 and PBS treated groups.

2. In vitro experiments.
 Splenic CD4⁺T cells derived from RORγt-Tg mice were cultured with different concentrations of A213 (0, 0.01, 0.1, 1 μM) in vitro, and we investigated 1) the expression of CD25 on CD4⁺T cells, 2) the production of IL-2 from CD4⁺T cells, and 3) the proportion of IL-17⁺IFNγ^–, IL-17^–IFNγ⁺, and IL-17⁺IFNγ⁺ cells in CD4⁺CD25⁺T cells.

Results: 1. In vivo experiments.
1) A213 significantly recovered the salivary secretion in RORγt-Tg mice compared with PBS (changes in saliva volume at day 14; 1.3±0.3 in PBS group, 3.1±1.4 in A213 group, P< 0.05). 2) Infiltration of mononuclear cells in salivary glands was dramatically improved in A213- compared with PBS-treated group. The focus score at day 14 was significantly lower in A213- than in PBS-treated group (2.5±0.6 in PBS-treated group, 0.3±0.3 in A213 treated-group, P< 0.05). 3) The proportion of CD4⁺CD25⁺cells in CD4⁺T cells of spleen was comparable between A213-and PBS-treated group. On the other hand, the proportion of CD4⁺CD25⁺cells in CD4⁺T cells of cLNs was significantly lower in A213- than PBS- treated group (P=0.007). 4) The proportions of both CD4⁺CD25⁺Foxp3⁺ and CD4⁺CD25⁺Foxp3^–cells in CD4⁺T cells of cLNs were significantly decreased in A213- than PBS-treated group (P< 0.05). 5) The mean fluorescence intensity (MFI) of CD69 on CD4⁺CD25⁺Foxp3^–cells in cLNs was significantly lower in A213- than PBS-treated group (P< 0.05), while no significant difference was detected in CD69 on CD4⁺CD25⁺Foxp3⁺cells.

2. In vitro experiments.
1) A213 (0, 0.01, 0.1, 1 μM) significantly suppressed the expression of CD25 on CD4⁺T cells derived from RORγt-Tg mice in a dose dependent manner. 2) A high concentration of A213 (1 μM) significantly suppressed the IL-2 production from CD4⁺T cells derived from RORγt-Tg mice. 3) IFNγ^–IL-17⁺cells were significantly decreased by A213 (0.1, 1 μM), while IFNγ⁺IL-17^– and IFNγ⁺IL-17⁺cells were significantly decreased by only a high concentration of A213 (1 μM) in CD4⁺CD25⁺cells (P< 0.001).

Conclusion:  RORγt antagonist could suppress the sialadenitis like SS via inhibition of CD4⁺CD25⁺cells in cLNs and have potential to be a new promising therapy for SS patients.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/ror%ce%b3t-antagonist-attenuates-experimental-sialadenitis-like-sjogrens-syndrome-via-inhibition-of-cd25-expression-on-cd4-t-cells/