Blanchard D K, Wei S, Duan C, Pericle F, Diaz J I, Djeu J Y
Department of Medical Microbiology and Immunology, University of South Florida College of Medicine, Tampa, USA.
Blood. 1995 Jun 1;85(11):3173-82.
The lysis of antigen presenting cells (APCs) by cytotoxic T lymphocytes (CTLs) may be one mechanism whereby an immune response is downregulated by Staphylococcus superantigens. Disappearance of monocytes/macrophages from staphylococcal enterotoxin A (SEA)-activated peripheral blood mononuclear cell (PBMC) cultures, but not from control PBMC cultures was seen by flow cytometry. Recently, adenosine triphosphate (ATP) has been described as an effector molecule in CTL-mediated lysis of some murine tumor target cells. We have also shown that ATP caused the lysis of human macrophages, and that treatment of cells with interferon gamma (IFN gamma) rendered macrophages significantly more sensitive to ATP than untreated cells. To show that this purine nucleotide may play a role in modulating the immune system, we generated human CTLs that were stimulated with SEA, and used them as effector cells against SEA-pulsed autologous macrophages. CTLs were found to specifically lyse SEA-pulsed macrophages, while control, unpulsed, macrophages were unaffected. The addition of hexokinase, an enzyme that hydrolyzes ATP, significantly abrogated the killing of SEA-pulsed cells during the assay. In examining the mechanism of cytotoxicity, electron microscopy showed that macrophages incubated with both ATP and CTLs underwent necrosis, rather than apoptosis. From these results, it is suggested that ATP is released from CTLs during antigen presentation, and that IFN gamma-activated macrophages, which are inherently more sensitive to this mediator, are readily lysed and therefore removed from circulation, thus downregulating an immune response.
细胞毒性T淋巴细胞（CTLs）对抗原呈递细胞（APCs）的裂解可能是葡萄球菌超抗原下调免疫反应的一种机制。通过流式细胞术可观察到，在葡萄球菌肠毒素A（SEA）激活的外周血单核细胞（PBMC）培养物中，单核细胞/巨噬细胞消失，但在对照PBMC培养物中未出现这种情况。最近，三磷酸腺苷（ATP）已被描述为CTL介导的某些鼠类肿瘤靶细胞裂解中的一种效应分子。我们还表明，ATP可导致人巨噬细胞的裂解，并且用干扰素γ（IFNγ）处理细胞会使巨噬细胞对ATP的敏感性显著高于未处理的细胞。为了证明这种嘌呤核苷酸可能在调节免疫系统中发挥作用，我们制备了用SEA刺激的人CTLs，并将其用作针对SEA脉冲处理的自体巨噬细胞的效应细胞。发现CTLs能特异性裂解SEA脉冲处理的巨噬细胞，而对照的、未脉冲处理的巨噬细胞则未受影响。添加己糖激酶（一种水解ATP的酶）在检测过程中显著消除了SEA脉冲处理细胞的杀伤作用。在研究细胞毒性机制时，电子显微镜显示，同时与ATP和CTLs孵育的巨噬细胞发生坏死，而非凋亡。从这些结果表明，在抗原呈递过程中，ATP从CTLs释放，并且IFNγ激活的巨噬细胞，其本身对这种介质更敏感，容易被裂解并因此从循环中清除，从而下调免疫反应。
