Laboratory of Microbiology and Immunology, School of Pharmaceutical Sciences, University of Shizuoka, Shizuoka 422-8526, Japan.
J Immunol. 2013 Jul 1;191(1):448-55. doi: 10.4049/jimmunol.1203061. Epub 2013 Jun 3.
Lymphocyte homing to peripheral lymph nodes (PLNs) is mediated by multistep interactions between lymphocytes and high endothelial venules (HEVs). Heparan sulfate (HS) has been implicated in the presentation of chemokines on the surface of HEVs during this process. However, it remains unclear whether this cell surface presentation is a prerequisite for lymphocyte homing. In this study, we generated conditional knockout (cKO) mice lacking Ext1, which encodes a glycosyltransferase essential for HS synthesis, by crossing Ext1(flox/flox) mice with GlcNAc6ST-2-Cre transgenic mice expressing Cre recombinase in HEVs. Immunohistochemical studies indicated that HS expression was specifically eliminated in PLN HEVs but retained in other blood vessels in the cKO mice. The accumulation of a major secondary lymphoid tissue chemokine, CCL21, on HEVs was also abrogated without affecting CCL21 mRNA levels, indicating that HS presents CCL21 on HEVs in vivo. Notably, a short-term lymphocyte homing assay indicated that lymphocyte homing to PLNs was diminished in the cKO mice by 30-40%. Consistent with this result, contact hypersensitivity responses were also diminished in the cKO mice. The residual lymphocyte homing to PLNs in the cKO mice was dependent on pertussis toxin-sensitive Gi protein signaling, in which lysophosphatidic acid-mediated signaling was partly involved. These results suggest that chemokine presentation by HS on the surface of HEVs facilitates but is not absolutely required for lymphocyte homing.
淋巴细胞归巢至外周淋巴结(PLN)是通过淋巴细胞与高内皮静脉(HEV)之间的多步相互作用介导的。在这个过程中,肝素硫酸盐(HS)已被牵涉到在 HEV 表面呈现趋化因子。然而,尚不清楚这种细胞表面呈现是否是淋巴细胞归巢的先决条件。在这项研究中,我们通过将 Ext1(flox/flox)小鼠与在 HEV 中表达 Cre 重组酶的 GlcNAc6ST-2-Cre 转基因小鼠杂交,生成了缺乏编码 HS 合成所必需的糖基转移酶 Ext1 的条件性敲除(cKO)小鼠。免疫组织化学研究表明,HS 表达在 cKO 小鼠的 PLN HEV 中特异性消除,但在其他血管中保留。HEV 上主要次级淋巴组织趋化因子 CCL21 的积累也被消除,而不影响 CCL21 mRNA 水平,表明 HS 在体内在 HEV 上呈现 CCL21。值得注意的是,短期淋巴细胞归巢试验表明,淋巴细胞归巢至 PLN 的速度在 cKO 小鼠中降低了 30-40%。与该结果一致,cKO 小鼠的接触超敏反应也减弱了。cKO 小鼠中残留的淋巴细胞归巢至 PLN 依赖于百日咳毒素敏感的 Gi 蛋白信号,其中部分涉及溶血磷脂酸介导的信号。这些结果表明,HS 在 HEV 表面呈现趋化因子有助于但不是绝对必需的淋巴细胞归巢。