Studies on CD4-2 positive cells a unique T cell subset of fish

利用针对银鲫CD4-1、CD4-2和CD8α的单克隆抗体（mab），研究了CD4-2阳性细胞在鱼类适应性免疫中的作用。在2022财政年度（FY），通过三种体内实验研究了银麻鱼体内CD4-1、CD4-2和CD8α阳性淋巴细胞的动力学：(A)在CyHV-2感染期间；(B) CyHV-2感染后高温水处理；(C)接种CyHV-2减毒活疫苗。在实验(A)中，我发现CyHV-2感染后，CD4-1、CD4-2和CD8α阳性淋巴细胞的数量增加，这表明CD4-2阳性淋巴细胞在鱼体内对疱疹病毒感染而不是分枝杆菌感染发挥重要作用（在2021财年报道）。在实验(B)中，我发现CD4-1、CD4-2和CD8α阳性淋巴细胞在CyHV-2二次攻击后数量迅速增加，这表明在ht处理的鱼体内，二次免疫反应需要CD4-1和CD4-2阳性淋巴细胞的帮助。对于实验(C)，在随后的毒力病毒攻毒后，我注意到接种减毒活疫苗的银麻中CD4-2阳性淋巴细胞的数量显著增加，而CD4-1阳性淋巴细胞的数量没有显著差异。这些结果提示CD4-2阳性淋巴细胞与CD4-1阳性淋巴细胞在鱼体内具有不同的作用。

With the aid of monoclonal antibodies (mAbs) against CD4-1, CD4-2, and CD8α of ginbuna crucian carp (ginbuna), the roles of CD4-2 positive cells in the adaptive immunity of fish were investigated. In fiscal year (FY) 2022, the kinetics of CD4-1, CD4-2, and CD8α positive lymphocytes in ginbuna were studied through three kinds of in vivo experiments: (A) during cyprinid herpesvirus-2 (CyHV-2) infection; (B) under high-temperature water (HT) treatment after CyHV-2 infection; and (C) immunized with a live-attenuated vaccine against CyHV-2 infection. For experiment (A), I found that the number of CD4-1, CD4-2, and CD8α positive lymphocytes increased after CyHV-2 infection, indicating that CD4-2 positive lymphocytes play important roles against herpesvirus infection instead of Mycobacterial infection (reported in FY 2021) in fish. For experiment (B), I realized that the number of CD4-1, CD4-2, and CD8α positive lymphocytes increased rapidly after the secondary CyHV-2 challenge, indicating that the secondary immune responses require the help of both CD4-1 and CD4-2 positive lymphocytes in HT-treated fish. For experiment (C), after subsequent virulent virus challenge, I noticed that the number of CD4-2 positive lymphocytes significantly increased in ginbuna immunized with the live-attenuated vaccine whereas no significant difference was observed in CD4-1 positive lymphocytes. These results suggest that CD4-2 positive lymphocytes can have a different role from CD4-1 positive lymphocytes in fish.