Cell Cycle Inhibition in Systemic Autoimmunity

描述(由申请人提供)： 这个项目的重点是确定细胞周期抑制因子p21在正常免疫和自身免疫反应中的作用。细胞周期在决定细胞命运和分化状态方面起着至关重要的作用。因此，它受细胞周期蛋白、细胞周期蛋白依赖性蛋白激酶和细胞周期蛋白依赖性蛋白依赖蛋白抑制物等蛋白质复合体的高度调控，这些复合体又受外界刺激通过一系列细胞内信号通路进行调节。我们发现在狼疮易感雄性BXSB小鼠的活化/记忆(CD44H1)表型的CD4+T细胞中存在高水平的某些CDKI，包括p21、p18和p27。这种T细胞在狼疮中普遍增加，我们推测反复刺激自身抗原反应性T细胞可能会导致类似于复制衰老的状态，在这种状态下，T细胞不再循环，但对凋亡具有抵抗力，积累并转录促进自身免疫的促炎细胞因子。为了测试这种可能性，我们产生并检测了p21缺陷的狼疮易感小鼠，并对p27基因敲除的自身免疫小鼠进行了初步研究。缺乏p21的雄性BXSB小鼠表现出明显的疾病减轻，与增强T和B淋巴细胞的凋亡以及显著减少激活/记忆的CD4+T细胞的积累有关。对p27基因缺陷的雄性BXSB小鼠的初步研究也显示死亡率降低。为了进一步研究CDKI在自身免疫和正常免疫反应中的作用，提出了四个目标。第一个将确定p21缺乏对另一个遗传上不同的狼疮易患株NZB.NZW-Lbw5的影响，NZW-Lbw5是来自NZB和NZW小鼠的间隔特异性同源基因系。第二个目标将确定T细胞中p21的表达是否对自身免疫的发展至关重要。第三个目的是研究p21缺陷对外来抗原和LCMV感染的免疫反应的影响。最终目的将确定Fas诱导的细胞凋亡在BXSB-p21“7”小鼠中观察到的疾病减少中的作用。这些研究将对p21在系统自身免疫和宿主对外来抗原的反应中的意义和作用产生重要的新见解。

DESCRIPTION (provided by applicant): This project will focus on defining the role of the cell cycle inhibitor, p21, in normal immune and autoimmune responses. The cell cycle plays a critical role in determining the fate and differentiation state of cells. It is therefore highly regulated by complexes of proteins such as cyclin, cyclin-dependent kinases (CDKs) and CDK inhibitors (CDKIs)7 which in turn are regulated by external stimuli through a number of intracellular signaling pathways. We found that high levels of certain CDKIs, including p21, p18 and p27 are present in activated/memory (CD44hl) phenotype CD4+ T cells in lupus-prone male BXSB mice. Such T cells are commonly increased in lupus and we postulated that repeated stimulation of self-antigen-reactive T cells might lead to a state similar to "replicative senescence", where T cells are no longer cycling, but are resistant to apoptosis, accumulate and transcribe autoimmune-promoting pro-inflammatory cytokines. To test this possibility, we generated and examined lupus-prone mice deficient in p21 and have performed preliminary studies of p27 knockout autoimmune mice. Male BXSB mice lacking p21 exhibited marked reduction in disease associated with enhanced apoptosis of T and B lymphocytes and significantly decreased accumulation of activated/memory CD4+ T cells. Initial studies of p27- deficient male BXSB mice also revealed reduced mortality. To further examine the role of CDKIs in autoimmunity and normal immune response four aims are proposed. The first will determine the effect of p21 deficiency on another genetically distinct lupus-prone strain, NZB.NZW-Lbw5, an interval-specific congenic line derived from NZB and NZW mice. The second aim will determine whether expression of p21 in T cells is critical for the development of autoimmunity. The third aim will examine the effect of p21 deficiency on immune responses to a foreign antigen and LCMV infection. The final aim will determine the role of Fas-induced apoptosis in the disease reduction observed in BXSB-p21"7" mice. These studies should yield important new insights into the significance and role of p21 in systemic autoimmunity and in host response to foreign antigens.