P CARINII-EPITHELIAL INTERACTIONS MEDIATE INFLAMMATION

卡氏肺囊虫在免疫功能低下的患者中产生危及生命的肺炎（PCP）。重要的是，PCP的临床严重程度往往与患者对卡氏杆菌的炎症反应能力密切相关，而不是与机体负荷密切相关。肺泡上皮细胞（AECs）与卡氏假杆菌密切相互作用，这些细胞在启动炎症反应中的重要作用越来越被认识到。本研究的假设是，aec在肺泡腔室对卡氏假单胞菌的初始检测和识别中起关键作用，卡氏假单胞菌与肺泡上皮的相互作用刺激趋化因子分泌，并发出信号，特异性地向感染部位募集炎症细胞。当卡氏假杆菌感染的SCID小鼠的免疫功能恢复时，T淋巴细胞和巨噬细胞只被募集到感染部位。除了清除感染外，这种炎症反应还会导致肺部的“旁观者”损伤。我们的初步数据扩展了这些观察结果，证明β趋化因子和β趋化因子受体CCR1和CCR2在感染SCID小鼠重组后和接种免疫能力小鼠后在体内高表达。此外，我们还发现，在体外，P. carinii与AECs的特异性附着模拟了tnf - α和β趋化因子基因的分泌。本研究的具体目的是：1)表征P. carinii刺激aec分泌趋化因子的能力，并诱导CD4+ T细胞趋化。2)确定体内暴露于卡氏杆菌后肺泡表面的早期趋化因子信号是否需要CD4+ T细胞。3)利用CCR1和2敲除小鼠，确定β趋化因子在细胞募集和对卡氏疟原虫抗性中的作用。4)确定CCR1和CCR2在T细胞募集、有机体清除和肺损伤中的作用，在一个具有良好特征的卡氏假杆菌诱导的肺部炎症模型中。本提案的目的是了解对卡氏假单胞菌的炎症反应，以便制定策略来规避由卡氏假单胞菌引起的宿主肺损伤。

Pneumocystis carinii produces life-threatening pneumonia (PCP) in immunocompromised patients. Importantly, the clinical severity of PCP often correlates more closely with a patient's ability to mount an inflammatory response against P. carinii than with organism burdens. Alveolar epithelial cells (AECs) interact closely with P. carinii, and the important role of these cells in initiating inflammatory responses is becoming increasingly recognized. The hypothesis of this proposal is that AECs play a critical role in the initial detection and recognition of P. carinii in the alveolar compartment, and that the interaction of P. carinii with the alveolar epithelium stimulates chemokine secretion, and signals the recruitment of inflammatory cells specifically to sites of infection. When immune function is restored to P. carinii-infected SCID mice, T lymphocytes and macrophages are recruited only to sites of infection. In addition to clearing infection, this inflammatory response also results in "bystander" injury to the lung. Our preliminary data extends these observations by demonstrating that beta-chemokines and the beta-chemokine receptors CCR1 and CCR2 are highly expressed in vivo after reconstitution of infected SCID mice, and after inoculation of immunocompetent mice. In addition, we show that the specific attachment of P. carinii to AECs, in vitro, simulates the secretion of TNF-alpha and beta-chemokine gene expression. The specific aims of this proposal are designed to: 1) characterize the ability of P. carinii stimulated AECs to secrete chemokines, and induce the chemotaxis of CD4+ T cells. 2) determine whether CD4+ T cells are required for the early chemokine signals at the alveolar surface following in vivo exposure to P. carinii. 3) determine the role of beta-chemokines in cell recruitment and in resistance to P. carinii by utilizing CCR1 and 2 knockout mice. 4) determine the role of CCR1 and CCR2 in T cell recruitment, organism clearance, and lung injury in a well-characterized model of P. carinii-induced pulmonary inflammation. The goal of this proposal is to understand the inflammatory response to P. carinii so that strategies may be developed to circumvent the lung injury that results from the host response to P. carinii.