CCL28  (趋化因子 CCL28)

CCL28，也称为粘膜相关上皮趋化因子 (MEC)、CCK1 和 SCYA28，是一种趋化因子。在不同的粘膜部位组成型表达，包括唾液腺和乳腺、气管以及结肠，以及小肠。 CCL28 已被归类为在稳态淋巴细胞运输中重要的组成型趋化因子，可以与 CCR3 和 CCR10 结合。其中，CCL28 可以趋化表达 CCR10 的 CD4 和 CD8 T 细胞群，以及表达 CCR3 的嗜酸性粒细胞的迁移。然而在肠粘膜中，很少有 T 细胞表达 CCR10 。而在 B 细胞群中，CCR10 可以由 IgA 浆母细胞和 IgA 分泌细胞（即浆细胞）选择性表达，在将浆母细胞归巢至肠外效应部位方面起着关键作用^[1]。CCL28 在结肠中组成型表达，但其水平可以通过促炎细胞因子和某些细菌产物增加，在效应细胞募集到上皮损伤部位的过程中发挥作用。CCL28 可以作为粘膜表面的统一免疫刺激剂，涉及 IgA 表达细胞向乳腺、唾液腺、肠和其他粘膜组织的迁移。另外，CCL28 对革兰氏阴性和革兰氏阳性细菌以及真菌表现出广谱的抗菌活性，如铜绿假单胞菌和肺炎克雷伯菌。进一步的研究也表明，CCL28 C 末端带正电荷的氨基酸显着促进了蛋白质的抗菌活性，其特有的疏水性和两亲性也有助于其杀伤活性^[2]。

CCL28, also known as mucosal associated epithelial chemokine (MEC), CCK1, and SCYA28, is a chemokine. It is expressed in various mucosal sites, including salivary glands and mammary glands, trachea and colon, and small intestine. CCL28 has been classified as an important component chemokine in homeostasis lymphocyte transport and can bind to CCR3 and CCR10. Among them, CCL28 can chemotactic CCR10 expression of CD4 and CD8 T cell populations, as well as CCR3 expression of eosinophils migration. However, in the intestinal mucosa, few T cells express CCR10. In contrast, in the B-cell population, CCR10 can be selectively expressed by IgA plasma mother cells and IgA-secreting cells (i.e. plasma cells), which play a key role in homing plasma mother cells to extraintestinal effector sites^[1]. CCL28 is constitutively expressed in the colon, but its levels can be increased by pro-inflammatory cytokines and certain bacterial products that play a role in effector cell recruitment to sites of epithelial injury.CCL28 can act as a unifying immunostimulant on the mucosal surface and is involved in the migration of IgA-expressing cells to the breast, salivary glands, intestine, and other mucosal tissues. In addition, CCL28 exhibits broad-spectrum antimicrobial activity against Gram-negative and Gram-positive bacteria as well as fungi, such as Pseudomonas aeruginosa and Klebsiella pneumoniae. Further studies also showed that the positively charged amino acids at the C-terminal end of CCL28 significantly contributed to the antibacterial activity of the protein, and its characteristic hydrophobicity and amphiphilicity also contributed to its killing activity^[2].

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