Laboratory of Pathology and Immunology of Aquatic Animals, Key Laboratory of Mariculture, Ministry of Education (KLMME), Ocean University of China, Qingdao, China.
Laboratory for Marine Fisheries Science and Food Production Processes, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China.
Front Immunol. 2021 Nov 11;12:765036. doi: 10.3389/fimmu.2021.765036. eCollection 2021.
CD28 is well known as a critical T-cell costimulatory receptor involved in T cell activation by binding to its ligands. In this study, CD28 was cloned, and its expression profiles were characterized in flounder (); variations of CD28+ cells after being stimulated with different types of antigens and the function of the CD28 costimulatory pathway on T-cell activation were investigated . consists of four exons and three introns, and the full-length cDNA of was 675-bp encoded 224 amino acids. The conserved motif (TFPPPF) binding to the CD80/86 ligand exists in the Ig-superfamily homology domain. The high expression of is in gills, PBLs, head kidney, and spleen. CD28+ cells were co-localized with CD4+ T lymphocytes but not on IgM+ B lymphocyte cells. Moreover, the expression of CD28 was significantly varied in flounder after being stimulated by keyhole limpet hemocyanin (KLH) at both the transcriptional and cellular levels, while no significant differences were observed between lipopolysaccharide (LPS) stimulation and the control group. Notably, treatment of PBLs cultured with CD28 molecule-specific antibody (anti-CD28 Abs) and PHA produced more cell colonies and stimulated the proliferation of cultured leukocytes compared to PHA stimulation alone and the control group, and a higher level of IL-2 was detected in the culture medium. Meanwhile, anti-CD28 Abs increased the percent of CD28+ cells (10.41 ± 1.35%), CD4+ T lymphocytes (18.32 ± 2.15%), and CD28+/CD4+ double-positive cells (6.24 ± 1.52%). This effect also resulted in significant variations in the genes of cell membrane-bound molecules, cytokines, and related signaling pathways in cultured leukocytes, with significant changes in the genes of and in the early stages of culture, and the expression of other molecules increased over time. These results proved the localization of the CD28 molecule on T lymphocytes in flounder, and anti-CD28 may act as the B7 ligand involved in T cell activation after antigen stimulation. These data provide a basis for a more in-depth study of the mechanism of the CD28 costimulatory pathway in T cell activation.
CD28 是一种重要的 T 细胞共刺激受体，通过与配体结合参与 T 细胞的激活。本研究克隆了 CD28，并研究了其在牙鲆中的表达谱；研究了不同类型抗原刺激后 CD28+细胞的变化，以及 CD28 共刺激途径对 T 细胞激活的功能。牙鲆 CD28 基因由 4 个外显子和 3 个内含子组成，全长 cDNA 为 675bp，编码 224 个氨基酸。CD80/86 配体结合的保守基序（TFPPPF）存在于 Ig 超家族同源结构域中。在鳃、PBLs、头肾和脾脏中，CD28 的表达水平较高。CD28+细胞与 CD4+T 淋巴细胞共定位，但不与 IgM+B 淋巴细胞共定位。此外，在转录和细胞水平上，牙鲆在受到血蓝蛋白（KLH）刺激后，CD28 的表达显著变化，而脂多糖（LPS）刺激与对照组之间无显著差异。值得注意的是，与 PHA 刺激组和对照组相比，用 CD28 分子特异性抗体（抗-CD28 Abs）和 PHA 处理培养的 PBLs 产生更多的细胞集落，并刺激培养的白细胞增殖，且培养基中检测到更高水平的 IL-2。同时，抗-CD28 Abs 增加了 CD28+细胞（10.41±1.35%）、CD4+T 淋巴细胞（18.32±2.15%）和 CD28+/CD4+双阳性细胞（6.24±1.52%）的比例。这一效应还导致培养白细胞中细胞膜结合分子、细胞因子和相关信号通路基因的显著变化，在培养早期 基因和 基因发生显著变化，其他分子的表达随时间增加。这些结果证明了 CD28 分子在牙鲆 T 淋巴细胞上的定位，并且抗-CD28 可能作为抗原刺激后参与 T 细胞激活的 B7 配体。这些数据为深入研究 CD28 共刺激途径在 T 细胞激活中的作用机制提供了依据。
