Whelan J P, Wysocki C J, Lampson L A
J Immunol. 1986 Oct 15;137(8):2567-71.
The olfactory neuroepithelium is unique in adult vertebrates in that bipolar sensory neurons are constantly dying and being replaced. The sensory neurons are also unusual because they are directly exposed to the external environment via their dendritic processes in the nasal cavity. Surveillance of this tissue by major histocompatibility complex (MHC) class I-restricted cytotoxic T cells would presumably serve as an important means of defense against foreign pathogens. Although adult brain shows a lack of class I molecules, it has not been reported if either proliferating neurons or sensory neurons in olfactory neuroepithelium also lack class I. To examine olfactory neuroepithelium, an antiserum against beta 2-microglobulin (beta 2-m), the invariant light chain associated with all class I molecules, was employed as a general probe in an immunocytochemical assay. beta 2-m was detected in columnar respiratory epithelium, blood vessel walls, and a small population of interstitial cells in the lamina propria, but no cell in the olfactory neuroepithelium stained for beta 2-m. Parallel patterns were obtained in the vomeronasal organ. These results suggest that lack of beta 2-m, and presumably class I, may be a general phenotype of neuronal cells regardless of their mitotic state or exposure to environmental antigens.
嗅觉神经上皮在成年脊椎动物中独具特色，在于双极感觉神经元不断死亡并被替换。感觉神经元也颇为特殊，因为它们通过鼻腔中的树突状突起直接暴露于外部环境。主要组织相容性复合体（MHC）I类限制性细胞毒性T细胞对该组织的监测大概是抵御外来病原体的重要防御手段。尽管成年大脑显示缺乏I类分子，但尚未有关于嗅觉神经上皮中增殖神经元或感觉神经元是否也缺乏I类分子的报道。为了检测嗅觉神经上皮，一种针对β2-微球蛋白（β2-m）的抗血清，即与所有I类分子相关的恒定轻链，在免疫细胞化学检测中用作通用探针。在柱状呼吸上皮、血管壁和固有层中的一小部分间质细胞中检测到β2-m，但嗅觉神经上皮中没有细胞被β2-m染色。在犁鼻器中也得到了类似的结果。这些结果表明，缺乏β2-m以及大概的I类分子，可能是神经元细胞的普遍表型，无论其有丝分裂状态或是否暴露于环境抗原。
