Supplementary Material for: Virus-Infected Human Mast Cells Enhance Natural Killer Cell Functions

Mucosal surfaces are protected from infection by both structural and sentinel cells, such as mast cells. The mast cell's role in antiviral responses is poorly understood; however, they selectively recruit natural killer (NK) cells following infection. Here, the ability of virus-infected mast cells to enhance NK cell functions was examined. Cord blood-derived<b> </b>human mast cells infected with reovirus (Reo-CBMC) and subsequent mast cell products were used for the stimulation of human NK cells. NK cells upregulated the CD69 molecule and cytotoxicity-related genes, and demonstrated increased cytotoxic activity in response to Reo-CBMC soluble products. NK cell interferon (IFN)-γ production was also promoted in the presence of interleukin (IL)-18. In vivo, SCID mice injected with Reo-CBMC in a subcutaneous Matrigel model, could recruit and activate murine NK cells, a property not shared by normal human fibroblasts. Soluble products of Reo-CBMC included IL-10, TNF, type I and type III IFNs. Blockade of the type I IFN receptor abrogated NK cell activation. Furthermore, reovirus-infected mast cells expressed multiple IFN-α subtypes not observed in reovirus-infected fibroblasts or epithelial cells. Our data define an important mast cell IFN response, not shared by structural cells, and a subsequent novel mast cell-NK cell immune axis in human antiviral host defense.

黏膜表面可通过结构细胞与哨兵细胞（如肥大细胞）抵御病原体感染。目前学界对肥大细胞在抗病毒应答中的作用认知尚浅，但已知其可在感染发生后选择性招募自然杀伤（NK）细胞。本研究考察了病毒感染的肥大细胞增强NK细胞功能的能力：我们采用呼肠孤病毒感染的脐带血来源人肥大细胞（Reo-CBMC）及其分泌产物刺激人NK细胞。实验结果显示，NK细胞可上调CD69分子与细胞毒性相关基因的表达，并在Reo-CBMC可溶性产物的刺激下展现出增强的细胞毒性活性；在白细胞介素（IL）-18存在时，NK细胞的干扰素（IFN）-γ生成能力也得到提升。体内实验方面，经皮下基质胶（Matrigel）模型注射Reo-CBMC的重症联合免疫缺陷（SCID）小鼠，可招募并激活小鼠NK细胞，该特性为正常人成纤维细胞所不具备。Reo-CBMC的可溶性产物包含IL-10、肿瘤坏死因子（TNF）、I型及III型干扰素。阻断I型干扰素受体可完全消除NK细胞的激活效应。此外，呼肠孤病毒感染的肥大细胞可表达多种干扰素-α亚型，而呼肠孤病毒感染的成纤维细胞或上皮细胞则无此类表达。本研究结果明确了结构细胞所不具备的一类重要的肥大细胞干扰素应答通路，以及人抗病毒宿主防御中一种全新的肥大细胞-NK细胞免疫轴。