Institute of Medical Immunology, Charité-Universitätsmedizin, Berlin, Germany.
J Immunother. 2011 Jun;34(5):428-37. doi: 10.1097/CJI.0b013e31821dcf23.
N-linked protein glycosylation represents an important cellular process for modifying protein properties. It resembles a cascade of various enzymatic reactions, in which class I α-mannosidases play a central role. We and others have recently shown that N-glycosylation plays a major role for immune functions. We now analyzed the expression and function of α-mannosidase I in CD4(+) naive and memory T cells studying human and murine T cells. Alpha-mannosidase I function was altered by (i) treatment with Kifunensine, a specific inhibitor class I α-mannosidases, (ii) synthetic inhibitory RNA, and (iii) overexpression by retroviral gene transfer. T-cell activation was evaluated by CD69 expression, cytokine production and proliferation. Our results demonstrate (i) that α-mannosidase I transcription is transiently downregulated after T-cell activation with either polyclonal anti-CD3/CD28 antibodies or allogeneic CD19(+) B cells, and (ii) that α-mannosidase I exerts an inhibitory effect on T-cell activation. It is interesting to note that the inhibitory effect was restricted to naive CD4(+) T cells in both systems, human T cells and murine transgenic CD4(+)OT-II cells, whereas human memory T cells and primed CD4(+)OT-II cells remained unaffected. Alpha-mannosidase I inhibition reduced the activation threshold for naive but not already primed CD4(+)OT-II cells as the cells were able to respond to lower ovalbumin peptide concentrations and increased the rejection potential of alloreactive T cells in vivo. Thus, complex N-glycans generated by enzymes such as α-mannosidase I inhibit the activation of naive T cells. These findings could be used to improve the ex vivo priming of naive T cells for adaptive T-cell therapies.
N-连接蛋白糖基化是一种重要的细胞过程，用于修饰蛋白质特性。它类似于一系列不同的酶促反应，其中 I 型α-甘露糖苷酶起着核心作用。我们和其他人最近表明，N-糖基化在免疫功能中起着主要作用。我们现在分析了 CD4(+)幼稚和记忆 T 细胞中 I 型α-甘露糖苷酶的表达和功能，研究了人类和鼠类 T 细胞。通过（i）用特异性抑制 I 型α-甘露糖苷酶的 kifunensine 处理、（ii）合成抑制性 RNA 和（iii）逆转录病毒基因转移过表达，改变了α-甘露糖苷酶 I 的功能。通过 CD69 表达、细胞因子产生和增殖来评估 T 细胞激活。我们的结果表明：（i）T 细胞激活后，无论是用多克隆抗 CD3/CD28 抗体还是同种异体 CD19(+)B 细胞激活，α-甘露糖苷酶 I 的转录都会短暂下调，（ii）α-甘露糖苷酶 I 对 T 细胞激活具有抑制作用。有趣的是，这种抑制作用仅限于两种系统中的幼稚 CD4(+)T 细胞，即人类 T 细胞和转基因 CD4(+)OT-II 细胞，而人类记忆 T 细胞和已激活的 CD4(+)OT-II 细胞不受影响。α-甘露糖苷酶 I 的抑制降低了幼稚但未被激活的 CD4(+)OT-II 细胞的激活阈值，因为这些细胞能够对较低浓度的卵清蛋白肽作出反应，并增加同种反应性 T 细胞在体内的排斥潜力。因此，像α-甘露糖苷酶 I 这样的酶产生的复杂 N-聚糖抑制了幼稚 T 细胞的激活。这些发现可用于改善用于适应性 T 细胞治疗的幼稚 T 细胞的体外激活。
