Puentes S M, Da Silva R P, Sacks D L, Hammer C H, Joiner K A
Laboratory of Parasitic Diseases, National Institutes of Allergy and Infectious Diseases, Bethesda, MD 20892.
J Immunol. 1990 Dec 15;145(12):4311-6.
The mechanism of serum resistance for infective promastigotes of Leishmania major was investigated. Prior results suggested that the mechanism of resistance was mediated at a step after C3 deposition. Equivalent amounts of C3b were deposited on serum-susceptible, noninfective promastigotes harvested from log stage cultures (LOG) and on C-resistant, infective, metacyclic promastigotes (MP) purified from stationary stage cultures. Whereas binding of C9 to LOG was stable during incubation in serum, C9 binding to MP was minimal and unstable, because molecules bound initially to MP were released with continued incubation. Failure to bind C9 was not a result of inability to activate C; the kinetics of C3, C6, and C9 consumption were similar for LOG and MP. Deposition of C5b-7 on MP was stable, indicating that the initial steps in terminal complex formation were intact. Instead, the majority of C5b-9 formed on MP was spontaneously released into the serum as SC5b-9. Residual C5b-9 on MP was released with 1 M NaCl. These data show that developmental modification of the promastigote membrane during transition from a noninfective to an infective stage blocks insertion of lytic C5b-9 into the promastigote membrane.
研究了硕大利什曼原虫感染性前鞭毛体血清抗性的机制。先前的结果表明，抗性机制在C3沉积后的一个步骤中起介导作用。等量的C3b沉积在从对数期培养物（LOG）收获的血清敏感、非感染性前鞭毛体以及从稳定期培养物中纯化的C抗性、感染性、成熟前鞭毛体（MP）上。虽然在血清中孵育期间C9与LOG的结合是稳定的，但C9与MP的结合极少且不稳定，因为最初与MP结合的分子会随着持续孵育而释放。未能结合C9并非由于无法激活补体；LOG和MP的C3、C6和C9消耗动力学相似。C5b - 7在MP上的沉积是稳定的，表明末端复合物形成的初始步骤是完整的。相反，在MP上形成的大多数C5b - 9作为SC5b - 9自发释放到血清中。MP上残留的C5b - 9用1 M NaCl处理后释放。这些数据表明，前鞭毛体膜在从非感染性阶段过渡到感染性阶段的过程中发生的发育修饰会阻止溶解性C5b - 9插入前鞭毛体膜。
