T細胞和其它所有類型的血細胞均來源于骨髓中的造血干細胞（HSCs）。造血干細胞具有分化成血液中各種各樣細胞的能力，分化的*步則是轉變成多能祖細胞（MPPs）。
關于接下來的分化過程，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轉變成紅細胞和非淋巴白細胞的“”；另一條稱為淋巴路徑，即MPPs轉變成T細胞和B細胞的“”。而T細胞的接著會進入胸腺，在這里它們被稱作早胸腺祖細胞（ETPs）。
論文作者、賓夕法尼亞大學病理學教授Avinash Bhandoola表示：“如果目前關于T細胞發育的模型是正確的，那么ETPs就應該只能產生T細胞，而不能產生骨髓細胞（myeloid cells）。”
研究人員對此進行了驗證。他們首先應用表面標簽將小鼠胸腺里的ETPs與其它細胞分開，然后將每個ETP細胞進行單獨培養，以觀察它們的分化情況。
結果令人吃驚。大多數盛有單個ETP細胞的培養皿都充滿了T細胞和骨髓細胞。這意味著大部分ETPs在進入胸腺后并不于轉變成T細胞，它們仍然保留著在T細胞和骨髓細胞間二選一的能力。接下來研究人員證實了，在正常的胸腺中，ETPs確實會產生骨髓細胞。Bhandoola說：“很難將觀測結果與過去我們對T細胞發育的看法協調起來。”
論文*作者、賓夕法尼亞大學博士后Jeremiah Bell說：“弄清T細胞的生活史及確定MPPs轉變成T細胞的步驟極為重要。現在我們想要弄清的是，ETPs怎樣作出決定，以轉變成骨髓細胞或T細胞。雖然我們的研究著重于基本科學，但它有助于弄清早期祖細胞怎樣導致T細胞性白血病。另外，胸腺中由ETPs產生的骨髓細胞也將引起我們的進一步關注。”（科學網 梅進/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.