Monaco S, Gehrmann J, Raivich G, Kreutzberg G W
Department of Neuromorphology, Max-Planck-Institute for Psychiatry, Martinsried, Germany.
J Neurocytol. 1992 Sep;21(9):623-34. doi: 10.1007/BF01191724.
Resident endoneurial macrophages form a prominent, but little recognized component of the PNS. We have studied immunocytochemically the distribution, morphology and immunophenotype of endoneurial macrophages in several normal peripheral nerves of the rat. In addition, we investigated the macrophage response following crush injury of the sciatic nerve. Resident endoneurial macrophages had a ramified morphology with processes oriented parallel to the long axis of nerve fibres. They were positive for several monocyte/macrophage markers such as ED1, ED2 and the recently-described MUC 101 and MUC 102 antibodies. They furthermore expressed the complement type three receptor, the CD4 antigen and MHC class I and II molecules. These results were consistent in all the peripheral nerves studied. In addition, 1000 rad of gamma-irradiation led to a strong reduction in the number of MHC class II-positive ramified cells in the peripheral nerves similar to that observed in other peripheral organs such as the heart. A considerable percentage of resident macrophages in the PNS and/or their precursor cells are therefore radiosensitive and could be related to the lineage of dendritic cells. Following crush injury, ED1-3-, OX-42-, MUC 101- and MUC 102-positive round macrophages were observed from 24 h postlesion onward at the site of trauma. In the distal part, they were observed to form strings of round, foamy macrophages probably involved in myelin phagocytosis. In contrast, the number of MHC class II-positive resident macrophages was only slightly increased at the site of trauma and in the distal part. These cells transformed from a ramified to a round morphology, but did not appear as typical strings of foamy macrophages. These results demonstrate that the PNS is provided with a resident macrophage population analogous in many respects to microglial cells in the CNS. These constitutively MHC class II-positive PNS microglial-like cells could act as the major antigen-presenting cells in the peripheral nerve. They may thus constitute a local immune defense system of the PNS with a function similar to that of microglial cells in the CNS.
神经内膜常驻巨噬细胞是周围神经系统（PNS）中一个显著但鲜为人知的组成部分。我们利用免疫细胞化学方法研究了大鼠多条正常外周神经中神经内膜巨噬细胞的分布、形态和免疫表型。此外，我们还研究了坐骨神经挤压伤后的巨噬细胞反应。神经内膜常驻巨噬细胞呈分支状形态，其突起与神经纤维的长轴平行。它们对多种单核细胞/巨噬细胞标志物呈阳性，如ED1、ED2以及最近描述的MUC 101和MUC 102抗体。它们还表达补体三型受体、CD4抗原以及MHC I类和II类分子。这些结果在所有研究的外周神经中都是一致的。此外，1000拉德的γ射线照射导致外周神经中MHC II类阳性分支状细胞数量大幅减少，类似于在心脏等其他外周器官中观察到的情况。因此，PNS中相当一部分常驻巨噬细胞和/或其前体细胞对辐射敏感，可能与树突状细胞谱系有关。挤压伤后，从损伤后24小时起，在创伤部位观察到ED1 - 3、OX - 42、MUC 101和MUC 102阳性的圆形巨噬细胞。在远端，观察到它们形成圆形、泡沫状巨噬细胞串，可能参与髓鞘吞噬作用。相比之下，创伤部位和远端MHC II类阳性常驻巨噬细胞的数量仅略有增加。这些细胞从分支状形态转变为圆形形态，但没有呈现出典型的泡沫状巨噬细胞串。这些结果表明，PNS拥有一群常驻巨噬细胞，在许多方面类似于中枢神经系统（CNS）中的小胶质细胞。这些组成性MHC II类阳性的PNS小胶质样细胞可能作为外周神经中的主要抗原呈递细胞。因此，它们可能构成PNS的局部免疫防御系统，其功能类似于CNS中的小胶质细胞。
