J. Exp. Med.：发现人记忆T细胞永久保持记忆

两个爱泼斯坦-巴尔病毒(Epstein-Barr virus, EBV)颗粒，图片来自维基共享资源。

根据2012年3月5日发表在Journal of Experimental Medicine期刊上的一篇研究论文，人类免疫系统产生的新记忆并不是以旧记忆消失为代价。

记忆杀伤性T细胞(memory killer T cell)是一类特化细胞(specialized cell)，是在对特定感染做出免疫应答后产生的。小鼠实验已表明产生新的记忆T细胞导致旧的记忆T细胞激活和随后的死亡，这可能是因为小鼠免疫系统只能容纳一定数目的记忆T细胞。

但是人类免疫系通过似乎不受这种空间限制的制约。在对大学生进行的追踪性研究中，来自美国明尼苏达大学医学院的Kristin Hogquist和同事们发现爱泼斯坦-巴尔病毒(Epstein-Barr virus, EBV，它是导致传染性单核细胞增多症产生的病因)导致的急性感染触发其他病毒特异性的记忆T细胞激活。但是这些细胞既不增殖也不会死亡，也就意味着它们的数目不受时间影响，一直保持不变。

因此，人类记忆T细胞只会随着时间的增加而不断堆积。这对免疫应答是否产生有益或者有害影响还有待进一步观察。(生物谷：towersimper编译)

doi:10.1084/jem.20112401
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Primary Epstein-Barr virus infection does not erode preexisting CD8+ T cell memory in humans

Oludare A. Odumade, Jennifer A. Knight, David O. Schmeling, David Masopust, Henry H. Balfour Jr., and Kristin A. Hogquist

Acute Epstein-Barr virus (EBV) infection results in an unusually robust CD8+ T cell response in young adults. Based on mouse studies, such a response would be predicted to result in attrition of preexisting memory to heterologous infections like influenza A (Flu) and cytomegalovirus (CMV). Furthermore, many studies have attempted to define the lymphocytosis that occurs during acute EBV infection in humans, but it is unclear whether bystander T cells contribute to it. To address these issues, we performed a longitudinal prospective study of primary EBV infection in humans. During acute EBV infection, both preexisting CMV- and Flu-specific memory CD8+ T cells showed signs of bystander activation, including up-regulation of granzyme B. However, they generally did not expand, suggesting that the profound CD8+ lymphocytosis associated with acute EBV infection is composed largely of EBV-specific T cells. Importantly, the numbers of CMV- and Flu-specific T cells were comparable before and after acute EBV infection. The data support the concept that, in humans, a robust CD8+ T cell response creates a new memory CD8+ T cell niche without substantially depleting preexisting memory for heterologous infections.