The gateway for invasion by the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) into human host cells is via the angiotensin-converting enzyme 2 (ACE2) transmembrane receptor expressed in multiple immune and nonimmune cell types. SARS-CoV-2, that causes coronavirus disease 2019 (COVID-19; CoV-19) has the unusual capacity to attack many different types of human host cells simultaneously via novel clathrin- and caveolae-independent endocytic pathways, becoming injurious to diverse cells, tissues and organ systems and exploiting any immune weakness in the host. The elicitation of this multipronged attack explains in part the severity and extensive variety of signs and symptoms observed in CoV-19 patients. To further our understanding of the mechanism and pathways of SARS-CoV-2 infection and susceptibility of specific cell- and tissue-types and organ systems to SARS-CoV-2 attack in this communication we analyzed ACE2 expression in 85 human tissues including 21 different brain regions, 7 fetal tissues and 8 controls. Besides strong ACE2 expression in respiratory, digestive, renal-excretory and reproductive cells, high ACE2 expression was also found in the amygdala, cerebral cortex and brainstem. The highest ACE2 expression level was found in the pons and medulla oblongata in the human brainstem, containing the medullary respiratory centers of the brain, and may in part explain the susceptibility of many CoV-19 patients to severe respiratory distress.

新型严重急性呼吸综合征冠状病毒 2 (SARS-CoV-2) 侵入人类宿主细胞的途径是通过在多种免疫和非免疫细胞类型中表达的血管紧张素转换酶 2 (ACE2) 跨膜受体。导致 2019 年冠状病毒病 (COVID-19; CoV-19) 的 SARS-CoV-2 具有通过新的网格蛋白和小窝独立内吞途径同时攻击许多不同类型的人类宿主细胞的不同寻常的能力，从而对多种细胞造成伤害，组织和器官系统，并利用宿主的任何免疫弱点。这种多管齐下的攻击的引发部分解释了在 CoV-19 患者中观察到的严重程度和广泛多样的体征和症状。为了进一步了解 SARS-CoV-2 感染的机制和途径以及特定细胞和组织类型和器官系统对 SARS-CoV-2 攻击的易感性，我们分析了 85 种人体组织中 ACE2 的表达，包括 21 种不同的组织。脑区、7 个胎儿组织和 8 个对照。除了在呼吸细胞、消化细胞、肾脏排泄细胞和生殖细胞中高表达 ACE2 外，在杏仁核、大脑皮层和脑干中也发现了高 ACE2 表达。在人脑干的脑桥和延髓中发现最高的 ACE2 表达水平，包含大脑的髓质呼吸中枢，这可能部分解释了许多 CoV-19 患者对严重呼吸窘迫的易感性。