Sacks D L
Cell Biology and Immunology Section, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892.
Infect Agents Dis. 1992 Aug;1(4):200-6.
The differentiation of Leishmania promastigotes from a noninfective procyclic stage to an infective metacyclic stage during growth within the midgut of their sand fly vectors or within axenic culture is accompanied by structural modifications of the surface lipophosphoglycan (LPG). The modifications are of two sorts: (a) a two- to three fold increase in size due to an increase in the number of phosphorylated saccharide units expressed and (b) a change in the composition of the terminal sugars of some of these units. The elongation of LPG on metacyclics promotes complement activation and C3 deposition in a nonlethal manner, thus opsonizing the promastigotes for attachment and uptake via macrophage receptors appropriate for subsequent intracellular survival. The down-regulation of terminally exposed galactose residues on metacyclic LPG appears to permit the selective release of infective-stage organisms from adhesion to midgut epithelial cells so as to make them available for subsequent transmission by bite.
利什曼原虫前鞭毛体在其白蛉载体的中肠内生长或在无细胞培养过程中，从无感染性的前循环阶段分化为有感染性的后循环阶段，伴随着表面脂磷壁酸（LPG）的结构修饰。这些修饰有两种类型：（a）由于表达的磷酸化糖单元数量增加，大小增加两到三倍；（b）其中一些单元末端糖的组成发生变化。后循环期LPG的延长以非致死方式促进补体激活和C3沉积，从而使前鞭毛体被调理，以便通过适合后续细胞内存活的巨噬细胞受体进行附着和摄取。后循环期LPG上末端暴露的半乳糖残基的下调似乎允许感染阶段的生物体从与中肠上皮细胞的粘附中选择性释放，从而使其可通过叮咬进行后续传播。
