Gebran S J, Yamamoto Y, Newton C, Klein T W, Friedman H
Department of Medical Microbiology and Immunology, University of South Florida, Tampa 33612-4799.
Infect Immun. 1994 Aug;62(8):3197-205. doi: 10.1128/iai.62.8.3197-3205.1994.
A/J mouse macrophages infected with Legionella pneumophila and treated with gamma interferon (IFN-gamma) in vitro developed potent antimicrobial activity. This antilegionella activity was independent of the macrophage capacity to generate reactive oxygen intermediates, since the oxygen radical scavengers catalase, superoxide dismutase, mannitol, and thiourea had no effect on the antilegionella activity of IFN-gamma-activated macrophages. Likewise, whereas the ability of IFN-gamma-activated macrophages to synthesize reactive nitrogen intermediates was markedly inhibited by the L-arginine (Arg) analogs, NG-monomethyl-L-arginine and L-aminoguanidine, as well as by incubation in L-Arg-free medium, their ability to inhibit the intracellular growth of L. pneumophila remained intact. The intracellular growth of L. pneumophila in A/J macrophages was inhibited by the iron(III) chelator desferrioxamine and reversed by Fe-transferrin as well as by ferric salts. Additionally, IFN-gamma-activated macrophages incorporated 28% less 59Fe(III) compared with nonactivated cells. Nonetheless, only partial blocking of growth restriction was observed when IFN-gamma-stimulated macrophages were saturated with iron(III). Indole-propionic acid, which appears to inhibit the biosynthesis of L-tryptophan (L-Trp), was an L-Trp-reversible growth inhibitor of L. pneumophila in macrophages, implying that the intracellular replication of this pathogen is also L-Trp dependent. However, an excess of exogenous L-Trp did not reverse the growth inhibition due to IFN-gamma, though a small synergistic effect was observed when the culture medium was supplemented with both iron(III) and L-Trp. We conclude that IFN-gamma-activated macrophages inhibit the intracellular proliferation of L. pneumophila by reactive oxygen intermediate- and reactive nitrogen intermediate-independent mechanisms and just partially by nutritionally dependent mechanisms. We also suggest that additional mechanisms, still unclear, may be involved, since complete reversion was never obtained and since at higher concentrations of IFN-gamma, iron(III) did not induce any significant reversion in the L. pneumophila growth inhibition.
体外感染嗜肺军团菌并经γ干扰素（IFN-γ）处理的A/J小鼠巨噬细胞产生了强大的抗菌活性。这种抗军团菌活性独立于巨噬细胞产生活性氧中间体的能力，因为氧自由基清除剂过氧化氢酶、超氧化物歧化酶、甘露醇和硫脲对IFN-γ激活的巨噬细胞的抗军团菌活性没有影响。同样，虽然L-精氨酸（Arg）类似物NG-单甲基-L-精氨酸和L-氨基胍以及在无Arg培养基中孵育会显著抑制IFN-γ激活的巨噬细胞合成活性氮中间体的能力，但它们抑制嗜肺军团菌细胞内生长的能力仍然完好。嗜肺军团菌在A/J巨噬细胞内的生长受到铁（III）螯合剂去铁胺的抑制，并被铁转铁蛋白以及铁盐逆转。此外，与未激活的细胞相比，IFN-γ激活的巨噬细胞摄取的59Fe（III）少28%。尽管如此，当用铁（III）使IFN-γ刺激的巨噬细胞饱和时，仅观察到生长限制的部分阻断。吲哚丙酸似乎抑制L-色氨酸（L-Trp）的生物合成，它是巨噬细胞中嗜肺军团菌的L-Trp可逆生长抑制剂，这意味着该病原体的细胞内复制也依赖L-Trp。然而，过量的外源性L-Trp并不能逆转IFN-γ引起的生长抑制，尽管当培养基同时添加铁（III）和L-Trp时观察到了小的协同效应。我们得出结论，IFN-γ激活的巨噬细胞通过独立于活性氧中间体和活性氮中间体的机制抑制嗜肺军团菌的细胞内增殖，仅部分通过营养依赖机制。我们还认为可能涉及仍不清楚的其他机制，因为从未实现完全逆转，并且在较高浓度的IFN-γ下，铁（III）并未在嗜肺军团菌生长抑制中诱导任何显著的逆转。
