Chang J T, Reiner S L
Abramson Family Cancer Research Institute and Department of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
Cold Spring Harb Symp Quant Biol. 2008;73:73-9. doi: 10.1101/sqb.2008.73.008. Epub 2008 Nov 6.
Numerous tissues in long-lived organisms are composed of short-lived cells. The continual regeneration of some barrier surfaces, for example, relies on adult stem cells that have the capacity to divide and produce one daughter cell destined for terminal differentiation and function and another daughter cell that renews the stem cell fate. The immune system of higher animals possesses a cellular component called lymphocytes, which face a similar need for regeneration. A lymphocyte that is recruited during an infection must give rise to cellular progeny that undergo terminal differentiation to eliminate an invading microbe, yet retain progeny that replace the recruited cell in order to maintain immunity to reinfection. Emerging evidence suggests that specifying the divergent cell fates necessary for immunity relies on the ability of the lymphocyte to exploit an evolutionarily conserved strategy for making kindred cells different--asymmetric cell division. Although the lymphocyte does not possess constitutive polarity, it appears to use a facultative interaction with another cell to nucleate unequal segregation of fate determinants relative to its plane of division. Herein, we propose that other mobile and nonadherent cells, such as blood and cancer stem cells, might exploit provisional interactions with their niche or microenvironment to achieve diversity among their daughter cells.
长寿生物体中的许多组织由寿命较短的细胞组成。例如，一些屏障表面的持续再生依赖于成体干细胞，这些干细胞能够分裂并产生一个注定要进行终末分化并行使功能的子细胞，以及另一个维持干细胞命运的子细胞。高等动物的免疫系统拥有一种称为淋巴细胞的细胞成分，它们也面临着类似的再生需求。在感染期间被招募的淋巴细胞必须产生经历终末分化以清除入侵微生物的细胞后代，但也要保留能够替代被招募细胞的后代，以维持对再次感染的免疫力。新出现的证据表明，确定免疫所需的不同细胞命运依赖于淋巴细胞利用一种进化上保守的策略来使同类细胞产生差异——不对称细胞分裂。虽然淋巴细胞不具有组成性极性，但它似乎利用与另一个细胞的临时相互作用，相对于其分裂平面使命运决定因子进行不等分离。在此，我们提出其他移动性和非黏附性细胞，如血液和癌症干细胞，可能利用与它们的生态位或微环境的临时相互作用，在其后代细胞中实现多样性。
