Zhu Yating, Chen Haokai, Zheng Yuying, Zhang Jiansong, Geng Ming, Fang Zhichao, Li Kang, Yang Jialong, Wei Xiumei
State Key Laboratory of Estuarine and Coastal Research, School of Life Sciences, East China Normal University, Shanghai, 200241, China.
State Key Laboratory of Estuarine and Coastal Research, School of Life Sciences, East China Normal University, Shanghai, 200241, China; Laboratory for Marine Biology and Biotechnology, Qingdao Marine Science and Technology Center, Qingdao, 266237, China.
Fish Shellfish Immunol. 2025 Oct;165:110537. doi: 10.1016/j.fsi.2025.110537. Epub 2025 Jul 1.
Interleukin-4/13 (IL-4/13) is a kind of bony fish cytokine, which is the homolog of Th2 cytokines IL-4 or IL-13 in mammals. Produced by activated T cells, these Th2 cytokines regulate B cell proliferation, survival, and antibody responses. Although IL-4/13 has been shown to participate in immune responses in bony fish, whether and how it regulates the teleost-specific IgT B cell subset, a lineage unique to bony fish remains unclear. In present study, we identified two conserved IL-4/13 from the Nile tilapia Oreochromis niloticus (OnIL-4/13A1 and OnIL-4/13A2), and suggested their wide expression in immunological tissues. OnIL-4/13A1 transcription was markedly upregulated in spleen and liver leukocytes upon bacterial infection, and can be dramatically induced by PHA- or CD3 mAb-induced T cell activation, suggesting activated T cells are a key cellular source of this cytokine. More importantly, we found that 2- or 4-days' in vivo administration of the recombinant OnIL-4/13A1 (rOnIL-4/13A1) caused an obvious expansion of IgT but not IgM B cells in tilapia. Further investigation demonstrated that this expansion was due to cellular proliferation, because the BrdU incorporation in IgT B cells was obviously increased, while the Erk1/2 and NF-κB phosphorylation that contributing to the proliferation was also enhanced in IgT B cells. Interestingly, as revealed by the Annexin V staining, we found that rOnIL-4/13A1 treatment elevated the apoptosis of IgT B cells, probably by initiating the Caspase-8/Caspase-3 pathway. Therefore, our results suggest that IL-4/13A1 involves in the anti-bacterial immune response of tilapia by promoting IgT B cell proliferation and maintaining IgT B cell hemostasis, thus shed novel light on the B cells response in bony fish.
白细胞介素-4/13（IL-4/13）是一种硬骨鱼细胞因子，是哺乳动物中Th2细胞因子IL-4或IL-13的同源物。这些Th2细胞因子由活化的T细胞产生，调节B细胞增殖、存活和抗体反应。尽管IL-4/13已被证明参与硬骨鱼的免疫反应，但它是否以及如何调节硬骨鱼特有的IgT B细胞亚群（硬骨鱼独有的谱系）仍不清楚。在本研究中，我们从尼罗罗非鱼（Oreochromis niloticus）中鉴定出两种保守的IL-4/13（OnIL-4/13A1和OnIL-4/13A2），并表明它们在免疫组织中广泛表达。细菌感染后，脾脏和肝脏白细胞中OnIL-4/13A1的转录明显上调，并且可以被PHA或CD3单克隆抗体诱导的T细胞活化显著诱导，表明活化的T细胞是这种细胞因子的关键细胞来源。更重要的是，我们发现体内给予重组OnIL-4/13A1（rOnIL-4/13A1）2天或4天会导致罗非鱼中IgT B细胞而非IgM B细胞明显扩增。进一步研究表明这种扩增是由于细胞增殖，因为IgT B细胞中BrdU掺入明显增加，而有助于增殖的Erk1/2和NF-κB磷酸化在IgT B细胞中也增强。有趣的是，通过膜联蛋白V染色发现，我们发现rOnIL-4/13A1处理提高了IgT B细胞的凋亡率，可能是通过启动半胱天冬酶-8/半胱天冬酶-3途径。因此，我们的结果表明IL-4/13A1通过促进IgT B细胞增殖和维持IgT B细胞稳态参与罗非鱼的抗菌免疫反应，从而为硬骨鱼的B细胞反应提供了新的线索。
