Gerrity R G
Am J Pathol. 1981 May;103(2):191-200.
A defined role in the atherogenic sequence is proposed for the circulating monocyte. The author has been able to demonstrate a "monocyte clearance system" in which large numbers of circulating monocytes invade the intima of lesion-prone areas in arteries, become phagocytic, and accumulate lipid. A fatty cell lesion results. Once lipid-laden, foam cells migrate back into the bloodstream by crossing the arterial endothelium. The ratio of penetrating monocytes to emerging foam cells decreases as fatty cell lesions develop until a one-to-one ratio is achieved in late fatty cell lesions, which do not progress further. Advanced fibroatherosclerotic plaques in the same animals do not show the same characteristics and have smooth muscle cell involvement. It would appear that advancement of the lesion is at least partially a result of failure of the monocyte clearance system to remove sufficient lipid. The invasion of monocytes and endothelial damage caused by foam cell clearance may, in late fatty lesions, contribute to plaque evolution by introducing growth factors from macrophages and platelets and allowing greater lipid influx. Elucidation of this system was facilitated by the examination of vessels from diet initiation onwards and by the observation of late nonprogressing fatty cell lesions. It is possible that this system exists in other models but has been overlooked by a predilection for the study of advanced lesions that prevails in the literature.
循环单核细胞在动脉粥样硬化形成过程中被认为具有特定作用。作者已证实存在一种“单核细胞清除系统”，大量循环单核细胞侵入动脉易损区域的内膜，变为吞噬细胞并积聚脂质，从而形成脂肪细胞病变。一旦充满脂质，泡沫细胞会穿过动脉内皮细胞回到血液中。随着脂肪细胞病变的发展，穿透的单核细胞与出现的泡沫细胞的比例会降低，直到在晚期脂肪细胞病变中达到一对一的比例，此时病变不再进一步发展。同一动物的晚期纤维粥样硬化斑块不具有相同特征，且有平滑肌细胞参与。看来病变的进展至少部分是由于单核细胞清除系统未能清除足够脂质所致。在晚期脂肪病变中，泡沫细胞清除引起的单核细胞侵入和内皮损伤可能通过引入巨噬细胞和血小板的生长因子并允许更多脂质流入，从而促进斑块演变。从开始饮食起就对血管进行检查以及观察晚期不进展的脂肪细胞病变，有助于阐明该系统。该系统可能存在于其他模型中，但由于文献中普遍倾向于研究晚期病变而被忽视。
