Rafting MHC-II domains in the APC (presynaptic) plasma membrane and the thresholds for T-cell activation and immunological synapse formation
Rafting MHC-II domains in the APC (presynaptic) plasma membrane and the thresholds for T-cell activation and immunological synapse formation
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DOI：
10.1016/j.imlet.2003.11.022
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发表时间：
2004-03-29
影响因子：
4.4
通讯作者：
Matkó, J
中科院分区：
文献类型：
--
作者：
Gombos, I;Detre, C;Matkó, J
T细胞中富含鞘糖脂和胆固醇的膜微区（筏）在触发和调节免疫突触（IS）中的T-H细胞活化中是重要的，这反过来可以控制淋巴结和外周中的T细胞库。然而，人们对“突触前侧”如何控制IS的形成和功能知之甚少。我们在此研究了流感病毒HA肽特异性的鼠IP 12 - 7 T（H）杂交瘤细胞在两种B淋巴瘤细胞A20和2 PK 3刺激下的激活信号和突触形成频率。共聚焦显微镜共定位和FRET数据consonantly揭示了集群分布和组成筏协会的一个主要部分的MHC-II分子在两个APC。共刺激分子（CD 80和CD 86），不与筏组成，在A20细胞中的表达水平低得多。如通过显微镜缀合测定所评估的，T细胞以比A20细胞高得多的信号强度响应2 PK 3 APC，与IS形成的频率具有良好的相关性。在2 PK 3细胞中通过胆固醇消耗破坏筏大大降低了T-H细胞活化信号的幅度，特别是在低肽抗原剂量下，类似于用T细胞上的mAb掩蔽CD 4。通过阻断T细胞上的LFA-1和APC上的CD 80，通过降低温度低于膜的相变或通过破坏肌动蛋白细胞骨架来降低IS形成的频率。这些数据共同表明，肽-MHC-II复合物的表面密度和亲和力/稳定性以及共刺激水平是有效的TCR识别和随后的T细胞信号的强度以及IS形成的主要决定因素，IS形成还需要在初始TCR信号后APC表面的细胞因子依赖性重塑。T细胞活化的阈值可以通过经由浓缩高亲和力配体来移植MHC-II结构域并由此促进T细胞用于感测低密度抗原来进一步设定。我们的数据还表明，B细胞，类似于树突状细胞，也可以提供T细胞与抗原无关的弱生存信号，可能与整合素的参与。(C)2004 Elsevier B. V.保留所有权利。
Glycosphingolipid- and cholesterol-rich membrane microdomains (rafts) in T-cells are important in triggering and regulation of T-H-cell activation in immunological synapses (IS), which in turn may control the T-cell repertoire in lymph nodes and at the periphery. It is less known, however, how the "presynaptic side" controls formation and function of IS. We investigated here activation signals and synapse formation frequency of murine IP12-7T(H) hybridoma cell specific to influenza virus HA-peptide upon stimulation with two B-lymphoma cells, A20 and 2PK3, pulsed with peptide antigen. Confocal microscopic colocalization and FRET data consonantly revealed clustered distribution and constitutive raft-association of a major fraction of MHC-II molecules in both APCs. Costimulatory molecules (CD80 and CD86), not associated constitutively with rafts, were expressed at much lower level in A20 cells. T-cells responded to 2PK3 APC with much higher signal strength than to A20 cells, in good correlation with the frequency of IS formation, as assessed by microscopic conjugation assay. Disruption of rafts by cholesterol depletion in 2PK3 cells largely decreased the magnitude of T-H cell activation signals, especially at low peptide antigen doses, similarly to masking CD4 with mAb on T-cells. The frequency of IS formation was reduced by blocking LFA-1 on T-cells and CD80 on APCs, by lowering the temperature below the phase transition of the membrane or by disrupting actin cytoskeleton. These data together suggest that the surface density and affinity/stability of peptide-MHC-II complexes and the costimulatory level are primary determinants for an efficient TCR recognition and the strength of the subsequent T-cell signals, as well as of the IS formation, which additionally requires a cytoskeleton-dependent remodeling of APC surface after the initial TCR signal. The threshold of T-cell activation can be further set by rafting MHC-II domains via concentrating high affinity ligands and promoting thereby T-cells for sensing low density antigen. Our data also demonstrate that B-cells, similarly to dendritic cells, could also provide T-cells with antigen-independent weak survival signals, likely associated with integrin engagement. (C) 2004 Elsevier B.V. All rights reserved.