Long-term consequences of regulatory T-cell-specific knockout of Notch2 in immune homeostasis.

ABSTRACT

AIMS: To investigate the long-term alterations in immune function and spontaneous inflammation in mice following specific knockout of Notch2 (Notch2KO) in Treg cells. MAIN METHODS: A Treg cell-specific Notch2 knockout mouse model was constructed, and the mice were named Notch2KO mice. The pathological changes and inflammatory cell infiltration in the lungs, skin, and liver of the mice at 2, 6, 9, and 12 months of age were evaluated by HE staining. The expression of Th1/Th2/Th17/Treg transcription factors was detected by Western blotting. The proportion of CD4 + T-cell subsets was determined by flow cytometry. The levels of Th1/Th2/Th17/Treg cytokines were measured by enzyme-linked immunosorbent assays (ELISAs). KEY FINDINGS: The expression level of Notch2 in Treg cells from the Notch2KO mice was significantly decreased compared with that in Treg cells from the control mice (P < 0.05). HE staining showed that compared with the control mice, the Notch2KO mice displayed spontaneous inflammation and had a large amount of inflammatory cell infiltration in the lungs and skin (P < 0.05). The number of Treg cells, the expression level of Foxp3, and the level of IL-10 were reduced in the Notch2KO mice compared with the control mice (P < 0.05), and these metrics further decreased with increasing age (P < 0.05). In contrast, the number of Th1/Th2 cells, the expression level of T-bet/GATA3, and the levels of Th1 cytokines (IFN-γ)/Th2 cytokines (IL-4, IL-5, and IL-13) were significantly increased in the Notch2KO mice (P < 0.05), and these metrics further increased with increasing age (P < 0.05). There was no significant change in the number of Th17 cells, the expression of RORγt, or the level of IL-17. Further analysis showed that the balance of Th1/Th2 and Treg/Th17 cells in the Notch2KO mice was shifted, and the ratio showed a downward trend over time (P < 0.05). SIGNIFICANCE: The number and function of Treg cells can be severely inhibited by a specific knockout of Notch2 in Treg cells, leading to immune disorders that gradually worsen over time.