Molecular mechanisms for TNF-mediated inhibition of B lymphocyte function

描述（由申请人提供）：衰老与个体产生保护性免疫应答的能力下降有关。了解老年人免疫功能受损的分子机制将有助于预防感染性疾病和改善老年人的生物学生活质量。 衰老的特征是血浆中促炎细胞因子（如TNF-α）水平升高，这些细胞因子可能会产生有害影响，因为它们与老年人多种致残性疾病的发病机制有关。我们假设老年人的这种促炎状态，称为炎症，损害了个体产生保护性抗体和对疫苗接种作出反应的能力。具体而言，我们的初步数据表明，老年典型的炎症反应增加也是由B淋巴细胞引起的，这对它们的功能产生了负面影响，包括经历免疫球蛋白（IG）的类别转换重组（CSR）的能力，这对于外源抗原特异性抗体的最佳效应子功能至关重要。 在这个R21应用中，我们将描述导致老年人B细胞应答降低的新分子机制，这些机制在未来应该能够用作改善老年人B细胞应答的新靶点。我们将评估从老年个体中离体分离的B细胞是否比年轻个体产生更多的TNF-α，确定哪种B细胞亚群产生TNF-α，以及与已知为该细胞因子主要来源的其他细胞类型相比产生多少。所解决的具体问题是来自老年个体的B细胞在IG类别转换中的内在缺陷是否是由于B细胞产生TNF-α的初始能力。 这也将与这些受试者体内抗流感疫苗应答相关。 我们将通过用TNF-α预孵育B细胞培养物来表征TNF-α损害B细胞进行CSR的能力的机制，并评估是否可以用添加到培养的B细胞中的抗TNF-α抗体来“拯救”体外IG类别转换。 结果测量将是我们先前发现的预测最佳B淋巴细胞应答的分子生物标志物。 在该R21申请中提出的实验提供了一种创新的方法来表征降低老年个体中的B细胞应答的进一步机制。这些研究应该对有效疫苗的关键开发产生直接影响，以保护老年人免受老年典型疾病的侵害。 公共卫生相关性：本文提出的研究探讨了降低人类B淋巴细胞和抗体反应的新分子机制，这对于对疫苗、传染病和癌症的最佳反应很重要。这些机制也可能有助于解释老年人炎症的总体增加，这有助于免疫系统，心脏和大脑的疾病。

DESCRIPTION (provided by applicant): Aging is associated with a decline in the ability of the individual to mount protective immune responses. Understanding the molecular mechanisms of the age-related impairment in immune functions will help to prevent infectious diseases and improve the biological quality of life in the elderly. Aging is characterized by increased plasma levels of pro-inflammatory cytokines such as TNF-alpha, and these can have deleterious effects as they are implicated in the pathogenesis of several disabling diseases of the elderly. We hypothesize that this pro-inflammatory status of the elderly, called inflammaging, impairs the capacity of the individual to make protective antibodies and to respond to vaccination. Specifically, our preliminary data indicate that the increased inflammatory response typical of old age is also contributed by B lymphocytes and this negatively impacts their function , including the ability to undergo class switch recombination (CSR) of immunoglobulin (Ig), critical for optimal effector function of antibodies specific for exogenous antigens. In this R21 application we will characterize novel molecular mechanisms leading to reduced B cell responses in the elderly which in the future should be able to be used as new targets for their improvement. We will evaluate whether B cells ex vivo isolated from elderly individuals make more TNF-alpha than those from younger ones, determine which B cell subset makes TNF-alpha, and how much compared to other cell types known to be primary sources of this cytokine. Particular questions addressed are whether the intrinsic defect of B cells from elderly individuals in Ig class switch is due to the initial ability of the B cell to make TNF-alpha. This will also be correlated with the in vivo anti-influenza vaccine response in these subjects. We will characterize the mechanisms by which TNF-alpha impairs the ability of B cells to undergo CSR by pre-incubating B cell cultures with TNF-alpha and evaluate if the in vitro Ig class switch can be "rescued" with an anti-TNF-alpha antibody added to cultured B cells. Outcome measures will be molecular biomarkers we have previously discovered to predict optimal B lymphocyte responses. The experiments proposed in this R21 application offer an innovative approach to characterize further mechanisms which decrease B cell responses in elderly individuals. These studies should have immediate impact on crucial development of effective vaccines to protect elderly individuals from diseases typical of old age. PUBLIC HEALTH RELEVANCE: The studies proposed here investigate novel molecular mechanisms for decreased human B lymphocyte and antibody responses, important for optimal response to vaccines, infectious diseases, and cancer. These mechanisms may also help to explain the overall increase seen in inflammation in the elderly, which contributes to disorders of the immune system, heart, and brain.