保姆細胞在決定免疫細胞生死方面有重要作用

    生物谷報導：根據一項由美國國家科學基金（NSF）支持的研究項目結果，「保姆細胞」（Nurse  cells）在免疫系統對抗感染的T細胞發育過程中決定其生死方面起著重要作用。這一結果發表在6月份的刊物《Experimental  Biology  and  Medicine》上。

    免疫系統中的T細胞又稱為胸腺細胞，它們存在於胸腔上部的胸腺中，是免疫系統中主要負責對抗外來抗原的細胞。胸腺功能的缺失將導致嚴重的免疫缺陷以及增加對於感染的易感性。胸腺產生的T細胞作用在於識別外來有害的入侵者。一旦入侵者被識別，T細胞就會嘗試消滅被感染的細胞。

    NSF的分子和細胞生物學部門項目主任Eve  Barak表示：「在較早的研究中，科學家認為胸腺中的保姆細胞只會消除沒有功能的胸腺細胞。而這項研究則顯示，保姆細胞在胸腺中的作用要比想像的大得多。」

    胸腺保姆細胞的名字來源於它們與胸腺細胞之間的密切關係。據報導，這些保姆細胞能將多達50個最終將死亡的胸腺細胞吸收入保姆細胞自身的胞體內。

   胸腺保姆細胞最早在1980年被發現。研究項目的主要負責人之一，來自紐約城市大學的生物學家Jerry  Guyden表示，這些保姆細胞的存在曾經在科學家之間引起爭論，因為科學家們很難相信一個細胞能內生於另一個細胞內。

    胸腺在大部分脊椎動物體內都存在，而且它們的結構和功能類似於人類胸腺。在肉類市場上常常有動物胸腺組織出售。

原始出處:

Experimental Biology and Medicine 232:780-788 (2007)

ORIGINAL RESEARCH ARTICLE

Thymic Nurse Cell Multicellular Complexes in HY-TCR Transgenic Mice Demonstrate Their Association with MHC Restriction

Marcia Martinez*, Michael Samms, Tonya M. Hendrix, Oluwaseun Adeosun, Mark Pezzano and Jerry C. Guyden,1

* Biology Department, Tuskegee University, Tuskegee, Alabama 36088; and Department of Biology, City College of New York, New York, New York 10031

To whom requests for reprints should be addressed at 1 Department of Biology, The City College of New York, 138th Street and Convent Avenue, New York, NY 10031. E-mail: [e-mail]

This study examines thymic nurse cell (TNC) function during T-cell development. It has been suggested that TNCs function in the removal of nonfunctional and/or apoptotic thymocytes and do not participate in major histocompatibility complex restriction. We analyzed TNCs isolated from both normal C57BL/6 mice and C57BL/6 TgN (TCRHY) mice (HY-TCR transgenic mice). Using confocal microscopic analyses of TNCs isolated from C57BL/6 animals, we showed that 75%–78% of the enclosed thymocyte subset was viable, and 87%–90% of these cells expressed both CD4 and CD8. CD4 and CD8 also were expressed on TNC thymocytes isolated from both male and female HY-TCR transgenic mice. The transgenic female thymus was shown to have 17 times more TNCs per milligram of thymus than the transgenic male thymus. TNCs from HY-TCR transgenic females were 8–10 µm larger than transgenic male TNCs, and the female TNCs contained five times more thymocytes within intracytoplasmic vacuoles, with less than 4% apoptosis. However, more than 42% of the thymocytes within transgenic male TNCs were apoptotic. The large number and size of TNCs containing viable thymocytes in the female transgenic thymus suggest that TNC function is not limited to the removal of apoptotic thymocytes. We believe that the selective uptake of viable double-positive thymocytes by TNCs in C57BL/6 and HY-TCR transgenic female mice provides evidence that this interaction occurs during the process of major histocompatibility complex restriction.

Key Words: thymic nurse cells • MHC restriction • thymocyte development • H-Y TCR Mice

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