Characterization Of Cell Surface Molecules Important For

本研究的目的是确定调节人幼稚T细胞活化的因素，特别是我们对NKG2D激活和LAIR-1抑制受体所起的作用感兴趣。在人类中，所有的CD8+T细胞都表达NKG2D，而在小鼠中，NKG2D仅由激活的和记忆的CD8+T细胞表达。我们纯化了人原始CD8+T细胞，表明NKG2D是TCR诱导的钙动员和增殖的共刺激受体。由此产生的效应细胞偏向于1型表型，并产生高水平的干扰素和肿瘤坏死因子。NKG2D配体、MHC-I类链相关(MIC)A、MICB和UL16结合蛋白在增殖细胞上表达，NKG2D表达下调。在培养上清液中加入稳态细胞因子IL-7和IL-15不仅能促进细胞增殖，而且比加入IL-2更能抑制NKG2D的表达下调。这些结果表明，NKG2D可以调节人初始CD8+T细胞的启动，这可能为增强和引导免疫反应提供了一种替代机制。 人白细胞相关免疫球蛋白样受体-1(LAIR-1)是一种跨膜糖蛋白，具有单一的胞外Ig样结构域和含有两个免疫受体酪氨酸抑制基序(ITIMs)的胞浆尾部。它在大多数人单核白细胞上结构性表达，并作为抑制性受体发挥作用。在这项研究中，我们发现新鲜分离的外周血T细胞在其LAIR-1的表达水平上是不同的。我们发现幼稚的T细胞表达最高水平的LAIR-1，甚至比记忆细胞更多。LAIR-1的交联会抑制新鲜分离的人初始T细胞和整个CD4+或CD8+T细胞群体中T细胞受体(TCR)介导的信号。TCR的交联会增加细胞表面LAIR-1的表达，这一过程需要p38 MAPK和ERK信号。综上所述，这些结果表明LAIR-1能够负向调节T细胞的功能，并且其在幼稚T细胞中的高水平表达表明它可能在免疫反应发展的早期阶段发挥作用。

The purpose of this research is to determine factors that regulate the activation of human naive T cells; in particular we are interested in the roles played by the NKG2D activation and LAIR-1 inhibitory receptors. In humans, all CD8+ T cells express NKG2D, but in mouse, it is only expressed by activated and memory CD8+ T cells. We purified human naive CD8+ T cells to show that NKG2D serves as a costimulatory receptor for TCR induced Ca2+ mobilization and proliferation. The resulting effector cells are skewed toward a type 1 phenotype and produce high levels of IFN- and TNF-. NKG2D ligands, MHC class I chain-related (MIC)A, MICB, and UL16-binding proteins are expressed on the proliferating cells and NKG2D is down-regulated. The addition of the homeostatic cytokines IL-7 and IL-15 to the culture medium not only enhances proliferation but also counteracts the down-regulation of NKG2D, more so than the addition of IL-2. These results indicate that NKG2D can regulate the priming of human naive CD8+ T cells, which may provide an alternative mechanism for potentiating and channeling the immune response. Human leukocyte-associated Ig-like receptor-1 (LAIR-1) is a transmembrane glycoprotein with a single extracellular Ig-like domain and a cytoplasmic tail containing two immunoreceptor tyrosine-based inhibition motifs (ITIMs). It is constitutively expressed on the majority of human mononuclear leukocytes and functions as an inhibitory receptor. In this study, we show that freshly isolated peripheral blood T cells are heterogeneous in their expression levels of LAIR-1. We have found that naive T cells express the highest levels of LAIR-1, even more than memory cells. The cross-linking of LAIR-1 inhibits T cell receptor (TCR) mediated signals in freshly isolated human naive T cells and whole populations of CD4+ or CD8+ T cells. TCR cross-linking increased cell surface expression of LAIR-1 in a process that requires p38 MAP kinase and ERK signaling. Altogether, these results indicate that LAIR-1 is capable of negatively regulating T cell functions, and its high level of expression by naive T cells suggests that it may function at an early stage in the development of an immune response.