Supraphysiological Levels of IL-2 in Jak3-Deficient Mice Promote Strong Proliferative Responses of Adoptively Transferred Naive CD8+ T Cells

• Main Authors: Gil-Woo Lee, Sung-Woo Lee, Juhee Kim, Young-Jun Ju, Hee-Ok Kim, Cheol-Heui Yun, Jae-Ho Cho
• Format: Article
• Language: English
• Published: Frontiers Media S.A. 2021-01-01
• Series: Frontiers in Immunology
• Subjects: interleukin-2; naive CD8+ T cells; antigen-independent proliferation; Janus kinase 3; activated CD4+ T cells; CD4+ regulatory T cells
• Online Access: https://www.frontiersin.org/articles/10.3389/fimmu.2020.616898/full

The antigen-independent, strong proliferative responses of naive CD8+ T cells have been well demonstrated in a particular strain of mice lacking IL-2 receptors. This type of proliferation is mainly driven by common gamma-chain (γc) cytokines, such as IL-2, IL-7, and IL-15, present at abnormally high levels in these mice. Similarly, in the present study, we showed that mice lacking Janus kinase 3 (Jak3), a tyrosine kinase crucial for γc cytokine signaling, could induce strong proliferation of adoptively transferred naive CD8+ T cells. This proliferation was also independent of antigenic stimulation, but heavily dependent on IL-2, as evidenced by the failure of proliferation of adoptively transferred IL-2 receptor alpha- and beta-chain-deficient naive CD8+ T cells. Consistent with this, Jak3–/– mice showed elevated serum levels of IL-2 compared to wild-type mice, and interestingly, IL-2 production was due to high levels of accumulation of activated CD4+ T cells in Jak3–/– mice along with defective CD4+ T regulatory cells. Collectively, these findings reveal previously unidentified unique immune contexts of Jak3–/– mice that cause robust IL-2-driven T cell expansion and have a clinical implication for designing a treatment strategy for human patients with loss-of-function genetic mutations of Jak3.