P CARINII-EPITHELIAL INTERACTIONS MEDIATE INFLAMMATION

卡氏肺孢子虫在免疫功能低下的患者中会产生危及生命的肺炎(PCP)。重要的是，PCP的临床严重性往往与患者对卡氏肺孢子虫产生炎症反应的能力密切相关，而不是与机体负担有关。肺泡上皮细胞(AECs)与卡氏肺孢子虫有密切的相互作用，这些细胞在启动炎症反应中的重要作用越来越为人们所认识。这一设想的假设是，AECs在最初发现和识别肺泡室中的卡氏肺孢子虫起关键作用，卡氏肺孢子虫与肺泡上皮细胞的相互作用刺激趋化因子的分泌，并发出炎症细胞特异性募集到感染部位的信号。当感染卡氏肺孢子虫的SCID小鼠的免疫功能恢复时，T淋巴细胞和巨噬细胞仅被招募到感染部位。除了清除感染外，这种炎症反应还会导致对肺部的“旁观者”损伤。我们的初步数据扩展了这些观察结果，证明在感染的SCID小鼠重建和免疫活性小鼠接种后，β-趋化因子和β-趋化因子受体CCR1和CCR2在体内高表达。此外，我们还发现，卡氏肺孢子虫在体外对血管内皮细胞的特异性附着模拟了肿瘤坏死因子-α的分泌和β-趋化因子基因的表达。该方案的具体目的是：1)研究卡氏肺孢子虫刺激的AECs分泌趋化因子的能力，并诱导CD4+T细胞趋化。2)确定卡氏肺孢子虫体内暴露后，肺泡表面早期趋化因子信号是否需要CD4+T细胞。3)利用CCR1和2基因敲除小鼠，确定β-趋化因子在细胞募集和对卡氏肺孢子虫耐药中的作用。4)在卡氏肺炎性肺炎模型中，确定CCR1和CCR2在T细胞募集、机体清除和肺损伤中的作用。这项建议的目的是了解卡氏肺孢子虫的炎症反应，以便制定策略来绕过宿主对卡氏肺孢子虫的反应所导致的肺损伤。

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.