Nat Immunol：毛囊也可触发免疫反应

近日，日本庆应大学等机构参加的一个国际研究小组在动物实验中发现，生长体毛的毛囊在感知到外部刺激或炎症风险时，会“召集”免疫细胞并使其分布到表皮中去，触发免疫反应。过敏性皮炎等疾病或许与这种机理有关。

研究人员在实验鼠的耳朵上贴、撕胶条以刺激其耳部毛囊，并用特殊的显微镜观察其皮肤内免疫细胞的动向。结果发现，约1小时之后毛囊处就集结了大批免疫细胞。其中，能够吸收异物、然后给其他免疫细胞标示攻击对象的树状细胞还经过毛囊向皮肤表皮移动。

研究小组在最新一期《自然—免疫学》（Nature Immunology）杂志网络版上报告说，他们研究毛囊组织后发现，有部分特定的毛囊细胞生成了能够“召集”免疫细胞的趋化因子。人类身上也有相同的现象。

以前，人们知道哺乳动物的体毛能够缓解外部撞击和紫外线的影响，具备物理防御功能，此次研究则表明，生长体毛的毛囊会将外部刺激视为异物入侵的征兆，从而触发免疫反应。这一发现将有助于开发治疗过敏性皮炎的方法。

doi:10.1038/ni.2353
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Stress-induced production of chemokines by hair follicles regulates the trafficking of dendritic cells in skin

Keisuke Nagao,1 Tetsuro Kobayashi,1 Kazuyo Moro,2 Manabu Ohyama,1 Takeya Adachi,1 Daniela Y Kitashima,1 Satoshi Ueha,3 Keisuke Horiuchi,4, 5 Hideaki Tanizaki,6 Kenji Kabashima,6 Akiharu Kubo,1, 5 Young-hun Cho,7 Bj?rn E Clausen,8 Kouji Matsushima,3 Makoto Suematsu,9, 10 Glaucia C Furtado,11 Sergio A Lira,11 Joshua M Farber,12 Mark C Udey7 & Masayuki Amagai1

Langerhans cells (LCs) are epidermal dendritic cells with incompletely understood origins that associate with hair follicles for unknown reasons. Here we show that in response to external stress, mouse hair follicles recruited Gr-1hi monocyte-derived precursors of LCs whose epidermal entry was dependent on the chemokine receptors CCR2 and CCR6, whereas the chemokine receptor CCR8 inhibited the recruitment of LCs. Distinct hair-follicle regions had differences in their expression of ligands for CCR2 and CCR6. The isthmus expressed the chemokine CCL2; the infundibulum expressed the chemokine CCL20; and keratinocytes in the bulge produced the chemokine CCL8, which is the ligand for CCR8. Thus, distinct hair-follicle keratinocyte subpopulations promoted or inhibited repopulation with LCs via differences in chemokine production, a feature also noted in humans. Pre-LCs failed to enter hairless skin in mice or humans, which establishes hair follicles as portals for LCs.