Angulo I, Rodríguez R, García B, Medina M, Navarro J, Subiza J L
Department of Immunology, University Hospital San Carlos, Madrid, Spain.
J Immunol. 1995 Jul 1;155(1):15-26.
Bone marrow (BM)-derived natural suppressor (NS) cells are strong inhibitors of lymphoproliferative responses. In this study we have assessed the involvement of nitric oxide (NO) in BM-derived NS activity, as detected in cocultures of BM and spleen cells stimulated with B cell (LPS) or T cell (Con A) mitogens. The results indicate that NS activity is readily inhibited by NG-monomethyl-L-arginine, a competitive inhibitor of NO synthase, or N-acetylcysteine, a free radical-scavenging thiol compound. High amounts of nitrite, a stable end product of NO, are detected only in supernatants of Con A- or LPS-stimulated spleen cells cocultured with BM cells enriched in NS activity (Fr3 cells). These amounts (15 to 55 microM) are strongly antiproliferative for both Con A and LPS responses, as was established with a nitrite curve made with a NO donor (sodium nitroprusside). Fr3 cells cultured alone release large quantities of NO and express inducible NO synthase (iNOS) mRNA upon LPS stimulation, but require spleen cells in cultures stimulated with Con A. Anti-IFN-gamma-neutralizing Abs blocked both NO production and NS activity, irrespective of the mitogen used; yet, only exogenous IFN-gamma is unable to promote successful NO production by Fr3 cells, but does induce detectable iNOS mRNA expression in these cells. Taken together the results indicate that: 1) NO is the major mediator of BM-derived NS activity; 2) BM cells enriched in NS activity produce large amounts of NO through an IFN-gamma-dependent iNOS induction.
骨髓（BM）来源的天然抑制细胞（NS）是淋巴细胞增殖反应的强效抑制剂。在本研究中，我们评估了一氧化氮（NO）在BM来源的NS活性中的作用，该活性在与B细胞（LPS）或T细胞（Con A）促有丝分裂原刺激的BM和脾细胞共培养物中检测到。结果表明，NS活性很容易被NO合酶的竞争性抑制剂NG-单甲基-L-精氨酸或自由基清除硫醇化合物N-乙酰半胱氨酸抑制。仅在与富含NS活性的BM细胞（Fr3细胞）共培养的Con A或LPS刺激的脾细胞上清液中检测到大量亚硝酸盐，亚硝酸盐是NO的稳定终产物。这些量（15至55 microM）对Con A和LPS反应均具有强烈的抗增殖作用，这是通过用NO供体（硝普钠）绘制的亚硝酸盐曲线确定的。单独培养的Fr3细胞在LPS刺激下释放大量NO并表达诱导型NO合酶（iNOS）mRNA，但在Con A刺激的培养物中需要脾细胞。抗IFN-γ中和抗体阻断了NO的产生和NS活性，无论使用何种促有丝分裂原；然而，仅外源性IFN-γ不能促进Fr3细胞成功产生NO，但确实能在这些细胞中诱导可检测到的iNOS mRNA表达。综合结果表明：1）NO是BM来源的NS活性的主要介质；2）富含NS活性的BM细胞通过IFN-γ依赖性iNOS诱导产生大量NO。
