Van Belle Tom, Grooten Johan
Molecular Immunology Unit, Department for Molecular Biomedical Research, Flanders Institute for Biotechnology (VIB) and Laboratory for Molecular Biology, University of Ghent, Gent-Zwijnaarde, Belgium.
Arch Immunol Ther Exp (Warsz). 2005 Mar-Apr;53(2):115-26.
The cytokine IL-15 performs numerous functions, such as promotion of growth and survival, on a plethora of cell types from both the lymphoid and non-lymphoid compartments. Therefore, mice genetically engineered to either lack or overexpress functional IL-15 display reduced immunological responses and leukemia, respectively. Surprisingly, IL-15 protein is hardly found in serum or body fluids. Due to the lack of a clear demonstration of its presence as protein,IL-15 was often referred to as a "ghost cytokine ". Recently, however, membrane-bound IL-15 was detected in both a membrane-anchored form and an IL-15Ralpha -bound form on monocytes. Interestingly, the latter complex can ben transpresented to cells expressing the intermediate-affinity IL-2/15Rbeta-gamma C receptor and thereby support the survival and proliferation of T cells. Moreover, overlapping promoter elements indicate a model of co-regulation of IL-15 and IL-15Ralpha by which IL-15 activities are controlled in a cell-contact-dependent manner. In this review, recent reports on IL-15 are combined with previous observations and discussed in terms of their functional consequences for CD4+ T cell responses.
细胞因子白细胞介素-15（IL-15）对来自淋巴和非淋巴区室的多种细胞类型具有多种功能，如促进生长和存活。因此，经基因工程改造而缺乏或过表达功能性IL-15的小鼠分别表现出免疫反应降低和白血病。令人惊讶的是，血清或体液中几乎检测不到IL-15蛋白。由于缺乏其作为蛋白质存在的明确证据，IL-15常被称为“幽灵细胞因子”。然而，最近在单核细胞上检测到了膜结合形式的IL-15，其以膜锚定形式和与IL-15Rα结合的形式存在。有趣的是，后者的复合物可以被转呈给表达中等亲和力IL-2/15Rβ-γC受体的细胞，从而支持T细胞的存活和增殖。此外，重叠的启动子元件表明存在一种IL-15和IL-15Rα共同调节的模式，通过这种模式，IL-15的活性以细胞接触依赖的方式受到控制。在这篇综述中，关于IL-15的最新报道与先前的观察结果相结合，并就其对CD4+T细胞反应的功能影响进行了讨论。
