Inducible IL-2 production and IL-2+ cell expansion are landmark events for T-cell activation of teleost

• Published in: Fish & shellfish immunology 2024-05, Vol.148, p.109515-109515, Article 109515
• Main Authors: Zhang, Jiansong, Li, Kang, Cao, Yi, Wang, Ding, Cheng, Jie, Gao, Haiyou, Geng, Ming, Yang, Jialong, Wei, Xiumei
• Format: Article
• Language: English
• Subjects: Adaptive immunity; Animals; Antibodies, Monoclonal; CD28 Antigens; CD3 Complex; Evolution; IL-2; Interleukin-2 - genetics; Lymphocyte Activation; Mice; Oreochromis niloticus; T-cell activation; T-Lymphocytes
• ISSN: 1050-4648; 1095-9947
• DOI: 10.1016/j.fsi.2024.109515

As a multipotent cytokine, interleukin (IL)-2 plays important roles in activation, differentiation and survival of the lymphocytes. Although biological characteristics and function of IL-2 have been clarified in several teleost species, evidence regarding IL-2 production at the cellular and protein levels is still scarce in fish due to the lack of reliable antibody. In this study, we developed a mouse anti-Nile tilapia IL-2 monoclonal antibody (mAb), which could specifically recognize IL-2 protein and identify IL-2-producing lymphocytes of tilapia. Using this mAb, we found that CD3+ T cells, but not CD3− lymphocytes, are the main cellular source of IL-2 in tilapia. Under resting condition, both CD3+CD4-1+ T cells and CD3+CD4-1- T cells of tilapia produce IL-2. Moreover, the IL-2 protein level and the frequency of IL-2+ T cells significantly increased once T cells were activated by phytohemagglutinin (PHA) or CD3 plus CD28 mAbs in vitro. In addition, Edwardsiella piscicida infection also induces the IL-2 production and the expansion of IL-2+ T cells in the spleen lymphocytes. These findings demonstrate that IL-2 takes part in the T-cell activation and anti-bacterial adaptive immune response of tilapia, and can serve as an important marker for T-cell activation of teleost fish. Our study has enriched the knowledge regarding T-cell response in fish species, and also provide novel perspective for understanding the evolution of adaptive immune system. •The anti-IL-2 mAb can identify IL-2 and IL-2-producing cells of tilapia.•CD3+ T cells are the main cellular source of IL-2 in tilapia.•IL-2 and IL-2-producing T cells are induced upon infection or T-cell activation.•IL-2 can serve as an activation marker for T cells in tilapia.