Effect Of The Secretion Of Tumor Cells On Immune System

The interaction between tumor cells and immune system is very complex. In normal situation,the immune system can recognize and eliminate the tumor cells. However,there are a lot of patients with tumor in clinic. The reason is the tumor cells escape the immunosurveillance whose mechanism is very complex. In general,the explanation is based on two aspects,one is that the tumor cells can passively escape the host immunosurveillance when the host immnue state is low and another is tumor cells can actively secrete factors to down-regulate immune function. The purpose of this paper is to study the mechanism of immunosuppression by tumor cells using a model rnimicing in vivo microinviroment.1, Due to the limitation of existing assay for evaluation of cell proliferation and cytotoxicity,in this study we developed a novel method. The characteristics of this method are:a,directly counting cell number without the influence of the metabolic state of the cells;b,discrimination of target cells from effector cells in cell-mediated cytotoxicity assay;c,less treatment step,and free-radioactivity;d,high sensitivity and reliability.2, Using the above assay,immunofluorescent labeled technique,and flow cytometry,the PBMC proliferation,apoptosis,necrosis,cell cycle,activation,cytokines and membrane marker were detected. The results showed that the number of PBMC reduced,but the activity of PBMC increased dose-dependently;the reduction of cell number resulted from necrosis and apoptosis;the supernatant of K562 cell lines were not able to block the cell cycle,but to promote it;the ratio of T cell subset and the expression of Thl and Th2 cytokines increased. These suggested the immunosuppression by K562 cell lines is mediated by reduction of the number of immunocytes.3, The effect of K562 cell lines supernatant on NO production by PBMC was investigated using the specific immunofluorescence probe DAF-2DA. The results showed that the K562 cell lines supernatant could promote the NO production byPBMC. Further study found all the activated PBMC(CD69+) produced NO,while not all the NO positive PBMC were activated. These suggested that NO plays a part role in the action of K562 cell lines supernatant to PBMC.4,The role of NO was investigated using NO inhibitor (L-NAME) and NO donor (SNP). O.OSmM of SNP could activate the PBMC,while above 0.5 mM of SNP could significantly induce PBMC necrosis,nevertheless,the higher concentration of SNP could not induce significant change of cytokine production,cell cycle,and ratio of PBMC subsets. These results indicated low concentration of NO is necessary for cell physiological activities,whereas high concentration of NO will impare cell physiological activities and even result in cell necrosis. The high concentration of NO production induced by K562 cell lines supernatant may only play the role of induction of PBMC necrosis.The conclusion of this study is that the immunosuppression by K562 cell lines supernatant is through reduction of the PBMC number. In the immunosuppression,NO plays a part but significant role. The originalities of this paper are:1,development of a a flow cytometry-based assay for quantitative analysis of cellular proliferation and cytotoxicity in vitro;2,the soluble secretion of K.562 cell lines reduce the number of PBMC,but promote the activity of PBMC in dose-dependent manner;3,soluble secretion of K562 cell lines can induce the NO production by PBMC,but NO only plays a part of the role of soluble secretion of K562 cell lines;4,establishing a in vitro model and giving some parameters for sreening and appraising anti-tumor medicine.