T細(xì)胞和其它所有類型的血細(xì)胞均來(lái)源于骨髓中的造血干細(xì)胞（HSCs）。造血干細(xì)胞具有分化成血液中各種各樣細(xì)胞的能力，分化的*步則是轉(zhuǎn)變成多能祖細(xì)胞（MPPs）。
關(guān)于接下來(lái)的分化過(guò)程，廣為接受的理論是存在兩條分化路徑。一條稱為骨髓路徑，即MPPs轉(zhuǎn)變成紅細(xì)胞和非淋巴白細(xì)胞的“”；另一條稱為淋巴路徑，即MPPs轉(zhuǎn)變成T細(xì)胞和B細(xì)胞的“”。而T細(xì)胞的接著會(huì)進(jìn)入胸腺，在這里它們被稱作早胸腺祖細(xì)胞（ETPs）。
論文作者、賓夕法尼亞大學(xué)病理學(xué)教授Avinash Bhandoola表示：“如果目前關(guān)于T細(xì)胞發(fā)育的模型是正確的，那么ETPs就應(yīng)該只能產(chǎn)生T細(xì)胞，而不能產(chǎn)生骨髓細(xì)胞（myeloid cells）。”
研究人員對(duì)此進(jìn)行了驗(yàn)證。他們首先應(yīng)用表面標(biāo)簽將小鼠胸腺里的ETPs與其它細(xì)胞分開，然后將每個(gè)ETP細(xì)胞進(jìn)行單獨(dú)培養(yǎng)，以觀察它們的分化情況。
結(jié)果令人吃驚。大多數(shù)盛有單個(gè)ETP細(xì)胞的培養(yǎng)皿都充滿了T細(xì)胞和骨髓細(xì)胞。這意味著大部分ETPs在進(jìn)入胸腺后并不于轉(zhuǎn)變成T細(xì)胞，它們?nèi)匀槐Ａ糁赥細(xì)胞和骨髓細(xì)胞間二選一的能力。接下來(lái)研究人員證實(shí)了，在正常的胸腺中，ETPs確實(shí)會(huì)產(chǎn)生骨髓細(xì)胞。Bhandoola說(shuō)：“很難將觀測(cè)結(jié)果與過(guò)去我們對(duì)T細(xì)胞發(fā)育的看法協(xié)調(diào)起來(lái)。”
論文*作者、賓夕法尼亞大學(xué)博士后Jeremiah Bell說(shuō)：“弄清T細(xì)胞的生活史及確定MPPs轉(zhuǎn)變成T細(xì)胞的步驟極為重要。現(xiàn)在我們想要弄清的是，ETPs怎樣作出決定，以轉(zhuǎn)變成骨髓細(xì)胞或T細(xì)胞。雖然我們的研究著重于基本科學(xué)，但它有助于弄清早期祖細(xì)胞怎樣導(dǎo)致T細(xì)胞性白血病。另外，胸腺中由ETPs產(chǎn)生的骨髓細(xì)胞也將引起我們的進(jìn)一步關(guān)注。”（科學(xué)網(wǎng) 梅進(jìn)/編譯）
（Nature），452, 764-767，J. Jeremiah Bell，Avinash Bhandoola
The earliest thymic progenitors for T cells possess myeloid lineage potential
J. Jeremiah Bell1 & Avinash Bhandoola1
Department of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA
Correspondence to: Avinash Bhandoola1 Correspondence and requests for materials should be addressed to A.B. (: bhandooa@mail.med.upenn.edu).
There exists controversy over the nature of haematopoietic progenitors of T cells. Most T cells develop in the thymus, but the lineage potential of thymus-colonizing progenitors is unknown. One approach to resolving this question is to determine the lineage potentials of the earliest thymic progenitors (ETPs). Previous work has shown that ETPs possess T and natural killer lymphoid potentials, and rare subsets of ETPs also possess B lymphoid potential1, suggesting an origin from lymphoid-restricted progenitor cells. However, whether ETPs also possess myeloid potential is unknown. Here we show that nearly all ETPs in adult mice possess both T and myeloid potential in clonal assays. The existence of progenitors possessing T and myeloid potential within the thymus is incompatible with the current dominant model of haematopoiesis, in which T cells are proposed to arise from lymphoid-2. Our results indicate that alternative models for lineage commitment during haematopoiesis must be considered.