Lim J S, Eck H P, Gmünder H, Dröge W
Division of Immunochemistry, Deutsches Krebsforschungszentrum, Heidelberg, Germany.
Cell Immunol. 1992 Apr;140(2):345-56. doi: 10.1016/0008-8749(92)90201-y.
Even moderate variations of the extracellular cysteine concentration were previously shown to affect T cell functions in vitro despite high concentrations of cystine. We therefore analyzed the membrane transport activities of T cells for cysteine and cystine, and the role of low molecular weight thiol in T cell-mediated host responses against a T cell tumor in vivo. A series of T cell clones and tumors including the highly malignant lymphoma L5178Y ESb and its strongly immunogenic variant ESb-D was found to express extremely weak transport activity for cystine but strong transport activity for cysteine. However, not all cells showed the expected requirement for cysteine (or 2-mercaptoethanol (2-ME)) in the culture medium. One group of clones and tumors including the malignant ESb-lymphoma did not respond to changes of extracellular cystine concentrations and was strongly thiol dependent. This group released only little acid soluble thiol (cysteine) if grown in cystine-containing cultures. The other T cell lines, in contrast, were able to maintain high intracellular GSH levels and DNA synthesis activity in cystine-containing culture medium without cystein or 2-ME and released substantial amounts of thiol. This group included the immunogenic ESb-D line. Additional thiol-releasing ESb variants were obtained by culturing large numbers of L5178Y ESb tumor cells in cultures without cysteine or 2-ME. All of these ESb variants showed a significantly decreased tumorigenicity and some of them induced cytotoxic and protective host responses even against the malignant ESb parent tumor. Taken together, our experiments suggest that the host response against a tumor may be limited in certain cases by the failure of the stimulator (i.e., the tumor) cell to deliver sufficient amounts of cysteine to the responding T cells.
先前研究表明，即便细胞外半胱氨酸浓度仅有适度变化，也会在体外影响T细胞功能，尽管存在高浓度的胱氨酸。因此，我们分析了T细胞对半胱氨酸和胱氨酸的膜转运活性，以及低分子量硫醇在T细胞介导的宿主对体内T细胞肿瘤反应中的作用。我们发现，一系列T细胞克隆和肿瘤，包括高恶性淋巴瘤L5178Y ESb及其强免疫原性变体ESb-D，对胱氨酸的转运活性极弱，但对半胱氨酸的转运活性很强。然而，并非所有细胞在培养基中都表现出对半胱氨酸（或2-巯基乙醇（2-ME））的预期需求。包括恶性ESb淋巴瘤在内的一组克隆和肿瘤对细胞外胱氨酸浓度的变化没有反应，且强烈依赖硫醇。如果在含胱氨酸的培养基中生长，这组细胞仅释放少量酸溶性硫醇（半胱氨酸）。相比之下，其他T细胞系能够在不含半胱氨酸或2-ME的含胱氨酸培养基中维持较高的细胞内谷胱甘肽水平和DNA合成活性，并释放大量硫醇。这组包括免疫原性ESb-D细胞系。通过在不含半胱氨酸或2-ME的培养基中培养大量L5178Y ESb肿瘤细胞，获得了其他释放硫醇的ESb变体。所有这些ESb变体的致瘤性均显著降低，其中一些甚至能诱导针对恶性ESb亲本肿瘤的细胞毒性和保护性宿主反应。综上所述，我们的实验表明，在某些情况下，宿主对肿瘤的反应可能会受到刺激细胞（即肿瘤细胞）未能向反应性T细胞提供足够量半胱氨酸的限制。
