Molecular Biology Of Mast Cell Growth And Differentiation

最近的一些观察显示了肥大细胞的生物学潜力。首先，我们发现人类肥大细胞具有合成和释放5-羟色胺(5-羟色胺)的能力。此外，肥大细胞和肥大细胞前体细胞通过与5-HT1a肥大细胞受体相互作用，在体外和体内对5-羟色胺产生趋化作用。这些观察指向了肥大细胞和5-羟色胺之间的一系列未知的相互作用。在临床上，这可能有助于解释为什么一些具有抗5-羟色胺特性的抗组胺药物被优先用于治疗某些形式的荨麻疹。 其次，吸入结晶二氧化硅会导致肺纤维化和矽肺。已有研究表明，肥大细胞在这些情况下发挥了作用。肥大细胞将如何影响病理学尚不清楚。因此，我们在体外和B6 Cg-KitW-sh肥大细胞缺陷小鼠中探索了肥大细胞与二氧化硅的相互作用。B6.Cg-KitW-sh小鼠在注入二氧化硅后没有出现炎症或明显的胶原沉积，而C57BL6野生型小鼠确实有这些发现。然后，我们检测了二氧化硅激活小鼠骨髓来源的肥大细胞的能力，包括脱颗粒、产生活性氧和炎症介质；以及二氧化硅对FcepsilonRI依赖的激活的影响。二氧化硅不能诱导肥大细胞脱颗粒。然而，暴露于二氧化硅后，肿瘤坏死因子-α、IL-13和单核细胞趋化蛋白-1、蛋白酶活性和ROS的产生呈剂量依赖性地增加，而FcepsilonRI刺激后的产生也增加。由于二氧化硅通过清道夫受体介导巨噬细胞的某些作用，我们首先确定肥大细胞表达清道夫受体，然后探讨SR-A和Marco的参与。SR-A、MARCO和SR-AMARCO KO小鼠BMMC中二氧化硅诱导的ROS形成、细胞凋亡和肿瘤坏死因子-α的产生均减少。这些发现表明，二氧化硅在一定程度上通过清道夫受体引导肥大细胞产生炎症介质。 我们还提出，与其他易感染HIV的细胞系不同，从未分化的骨髓来源的CD34多能前体体外培养的祖细胞肥大细胞(PrMCs)在其个体发育的有限时期内容易感染。随着感染的PrMCs在培养中成熟，它们失去了病毒进入所需的病毒趋化因子辅助受体的表达，并发育成长期存活的、潜伏感染的成熟组织肥大细胞，对新的感染具有抵抗力。PMCs在体内募集到不同的组织间是正常的，因此可能允许循环中的和潜在的对HIV敏感的pMCs群体将持续感染传播到不同的组织间。我们通过证明感染HIV的妇女既有循环中的pMCs，也有携带可诱导的传染性HIV的胎盘组织MCs，从而发现了这一效应。此外，在体外培养数周后，分离的潜伏感染的PLMCs可以诱导出能够感染异体激活的胎儿脐血单个核细胞的传染性病毒。 最后，我们研究了电离辐射对肥大细胞的影响。伽玛辐射有几种治疗适应症，包括骨髓移植和肿瘤消融。在免疫细胞中，淋巴细胞对伽马辐射的敏感性是众所周知的。然而，关于伽玛辐射对肥大细胞的影响的信息很少。因此，我们研究了人类和小鼠肥大细胞的存活和激活，包括与伽马辐射后的先天性和获得性免疫反应有关的机制。数据显示，人和小鼠肥大细胞对伽马辐射诱导的细胞毒性具有抵抗力，并且辐射不直接诱导肥大细胞脱颗粒。相反，观察到IgE介导的β-己糖苷酶释放和细胞因子产生的一过性减弱。肥大细胞保留了吞噬大肠杆菌颗粒的能力，并对TLR配体做出反应。在体内，照射小鼠皮肤中的肥大细胞数量没有减少。此外，肥大细胞在体内保留了对抗原的反应能力。因此，肥大细胞能够抵抗伽马辐射引起的细胞毒性效应和功能变化，并能够对伽马辐射后的先天和后天免疫激活信号做出反应。

The biologic potential of mast cells is shown by a number of recent observations. First, we have found that human mast cells have the ability to synthesize and release serotonin (5-HT). Further, mast cells and mast cell progenitors will chemotax to 5-HT both in vitro and in vivo by interacting with the 5-HT1A mast cell receptor. These observations point to a here-to-fore unrecognized set of interactions between mast cells and 5-HT. Clinically this may help explain why some antihistamines with antiserotonergic properties have found preferential use in the treatment of some forms of urticaria. Second, inhalation of crystalline silica results in pulmonary fibrosis and silicosis. It has been suggested that mast cells play a role in these conditions. How mast cells would influence pathology is unknown. We thus explored mast cell interactions with silica in vitro and in B6.Cg-KitW-sh mast cell deficient mice. B6.Cg-KitW-sh mice did not develop inflammation or significant collagen deposition following instillation of silica, while C57Bl6 wild-type mice did have these findings. We then examined the ability of silica to activate mouse bone marrow derived mast cells, including degranulation, production of reactive oxygen species and inflammatory mediators; and the effects of silica on FcepsilonRI-dependent activation. Silica did not induce mast cell degranulation. However, TNF-alpha, IL-13 and MCP-1; protease activity, and production of ROS were dose dependently increased following silica exposure; and production was enhanced following FcepsilonRI stimulation. As silica mediates some effects in macrophages through scavenger receptors, we first determined that mast cells expressed scavenger receptors; then explored the involvement of SR-A and MARCO. Silica-induced ROS formation, apoptosis and TNF-alpha production were reduced in BMMC obtained from SR-A, MARCO and SR-AMARCO KO mice. These findings demonstrate that silica directs mast cell production of inflammatory mediators, in part through scavenger receptors. We have also proposed that unlike other HIV-vulnerable cell lineages, progenitor mast cells (prMCs), cultured in vitro from undifferentiated bone marrow-derived CD34 pluripotent precursors, are susceptible to infection during a limited period of their ontogeny. As infected prMCs mature in culture, they lose expression of viral chemokine co-receptors necessary for viral entry and develop into long-lived, latently infected mature tissue mast cells, resistant to new infection. In vivo recruitment of prMCs to different tissue compartments occurs normally, thus possibly allowing populations of circulating and potentially HIV-susceptible prMCs to spread persistent infection to diverse tissue compartments. We found exidence to this effect by demonstrating that HIV-infected women have both circulating prMCs and placental tissue MCs that harbor inducible infectious HIV. Furthermore, infectious virus, capable of infecting allo-activated fetal cord blood mononuclear cells, could be induced in isolated latently-infected PLMCs after weeks in culture in vitro. Finally, we examined the effect of ionizing gamma-radiation on mast cells. Gamma-radiation has several therapeutic indications including bone marrow transplantation and tumor ablation. Among immune cells, susceptibility of lymphocytes to gamma-radiation is well known. However, there was little information on the effects of gamma-radiation on mast cells. We thus examined both human and murine mast cell survival and activation, including mechanisms related to innate and acquired immune responses following gamma-irradiation. Data revealed that human and murine mast cells were resistant to gamma-radiation-induced cytotoxicity and that irradiation did not directly induce mast cell degranulation. Instead, a transient attenuation of IgE-mediated beta-hexosaminidase release and cytokine production was observed. Mast cells retained the ability to phagocytose E. coli particles and respond to TLR ligands. In vivo, there was no decrease in mast cell numbers in skin of irradiated mice. Additionally, mast cells retained the ability to respond to antigen in vivo. Mast cells are thus resistant to the cytotoxic effects and alterations in function induced by gamma-radiation; and are able to respond to both innate and acquired immune activation signals following exposure to gamma-radiation.