自然弒細胞發生學的雙系模式：白血球介質15及21分別導引 CD56+Kir±lectis+ 弒細胞 及CD56±Kirlectin自然弒細胞(1/3)

Abstract

自然弒細胞的發生須經由介質15 作用，缺乏介質15 的基因轉移老鼠完全沒 有自然弒細胞，但是人類的自然弒細胞和老鼠不同，其細胞表面有CD56 、C-type lectin 及 KIR ，這些是老鼠所沒有的，更重要的是自然弒細胞可分泌 type I (IFN-r) 及 type II (IL-4)這兩種類型的自然弒細胞、和CD56 、C-type lectin 及 KIR 表現型的關係至今不明。 自然弒細胞和T-細胞由同一來分化的CD44 + CD25 - CD161 + T/NK 先驅細胞 分化而來，這一T/NK 細胞受介質 7 或轉錄因子Notch 、E2A 的作用分化為T- 細胞，相反的若受到介質15 及轉錄因子Id3 則分化為自然弒細胞，值得注意的 是，介質15 及介質7 它們有共同的受器rc ，因此我們可以利用流體細胞儀來分 離未分化的CD44 + CD25 - CD161 + rc + T/NK 先驅細胞，並將這細胞用來研究自然 弒細胞的分化及分生學，我們最有與趣的3 個問題： 1. CD56 + 及CD56 ± ：人類的自然弒細胞可分為CD56 + 及CD56 ± 二類，於Nature am 的發表的分析顯示CD56 + NK cells 可經由介質21 產生，但是其發生過程 詳細情形仍不清楚，和經由介質15 所產生的的CD56 + NK cell 的關係亦不明。 2. type I 及type II ：自然弒細胞和F helper 細胞一樣可為根據其分泌的介質分為 Type I 及type Type I 主要分泌IFN-r ，type II 主要分泌IL-4 而一般認為type I 及type II 是由同一個未成熟的type O 細胞產生的，但是最近Nature Immunol-py 21 所發表的報告顯示發生的過程是type II-type-o-type-I ，我們想 利用T/NK 先驅細胞，來分別這2 個模式。 3. C-lectin 及KIR ：人類的自然弒細胞和老鼠不同，不但有C-lectin 還用KIR 來 當做抗原受器(Trends Immunelop>001)我們認為C-lectin 可能是發生學上較早 的抗原受器較為原始也較為不具特定性。 總結以上相對於過去學者所用的功能性分析，我們將以發生學的觀點來研究 自然弒細胞的發生以期建立一個人類自然弒細胞的雙系模式： 介質15 及21 分別促成CD56 + Kir ± lectin + 等一型及CD56 ± Kir + lectin ± 第二型自然弒 細胞的生成，這個模式可用於台灣常見的鼻咽淋巴癌的分類，因此也具有相當的 臨床意義。

NK-cell development depends on interleukin 15, as shown by the complete absence of NK-cells in transgenic mice knocked out for either interleukin 15 or its receptor. However, mature human NK-cells in the peripheral blood differ from mouse NK-cells, with varying expression of surface NK-markers, such as CD56, C-type lectin, and KIR, and secretion of type I and type II cytokines. It is still unclear how the expression patterns of CD56, C-type lectins and KIRs are related to each other and to their functions, type I vs type II. NK-cells and T-cells arise from a common CD44+, CD25-, CD161+ bipotent T/NK precursor, which subsequently diverges into T-cells under interleukin 7, Notch and E2A, or alternatively into NK-cells under interleukin 15 and Id3. Id3 and E2A are both helix-loop-helix transcription factors, whereas interleukins 7 and 15 have a 4-a-helical-bundle structure using a common g-chain (gc) in their receptors. For the study of NK-cell development, we propose to isolate from bone marrow, thymus, or peripheral blood by flow cytometry the common bipotent CD44+, CD25-, CD161+, gc +, T/NK cells. They will be positively selected for interleukin 15 receptor and Id3, and negative selected for interleukin 7 receptor and E2A. We will then use a developmental approach to support, clarify, or refute previous functional-structural studies on 3 issues. (I) CD56 brigtht vs CD56 dim . Human NK-cells could be divided into a CD56 brigtht subset and a CD56 dim subset. Based on functional characterization (Natur e 2000) that showed expansion of CD56 dim NK-cells under interleukin 21, we want to show that NK-cell precursors will develop into either the CD56 brigtht subset in the presence of interleukin 15 or the CD56 dim subset in the presence of interleukin 21. (II) Type I vs Type II. In the classical dichotomy model, a common type zero NK cell will give rise to either type I NK cells secreting predominantly IFN-g and type II NK-cells secreting predominantly interleukin 4 and interleukin 13. However, functional analysis (Nature Immunology 2001) seems to indicate a type II-type 0-type I sequence. We will clarify the dichotomy vs sequential controversy by tracing back to the common bipotent precursors. (III) C-type Lectin vs KIR. Human NK-cells use both C-type lectins and KIRs as antigen receptors that recognize different structures of the MHC-1 molecules (Trends Immunology, 2001). We want to show that C-type lectin might represent a more primitive less specific antigen receptor earlier in the development of NK-cells. Using a developmental approach, we want to integrate previous functional-structural data into a dual lineage model for the development of mature human NK-cells in which interleukin 15 and interleukin 21 drive r espectively the development of CD56 brigtht KIR dim Lectin bright type I (IFN-g+) NK-cells and CD56 dim KIR bright Lectin dim type II (IL-13+) NK-cells. This model can then be applied to the study of sinonasal lymphoma, which is an EBV-associated NK-cell lymphoma rather common in Taiwan, and might contribute to the clinical management of these patients.