Chen Zhao-cong

Biologic characteristics of an immunosuppressive factor derived from a human lung cancer cell line

SummaryA 549, a human lung cancer cell line, spontaneously produces a tumor-derived immunosuppressive factor (TDSF) which inhibited PHA-stimulated T lymphocyte proliferation via a noncytotoxic mechanism. The inhibition increased in a dose-dependent pattern. The factor also markedly suppressed production of interleukin (IL-2) by PHA-stimulated lymphocytes and IL 2-dependent proliferation of activated lymphocytes. The fact that TDSF possessed very potent inhibitive action on IL-2 is especially noteworthy if we consider the use of IL-2 as immunotherapeutic agent. The synthesis of the factor was inhibited by mitomycin C, actinomycin D and cycloheximide, indicating that the factor is a genic product of A 549 cells. The factor is chemically a protein with a molecular weight greater than 150 KD and sensitve to extremes of pH, heating to 60 °C and trypsin treatment.

Effects of GAL10-SUC2 promoter combinations on SUC2 gene expression in S. cerevisiae

The plasmid series YEP51 delta n bearing GAL10-SUC2 promoter combinations were constructed by inserting SUC2 gene with different upstream deletions downstream GAL10 promoter on YEP51. After transforming yeast cells S. cerevisiae, the invertases expressed by each of the transformants were measured and analysed by means of PAGE. The results showed that: 1) The SUC2 gene with upstream deletion to at -636bp expressed high level glycosylated form of invertase under glucose derepression, while SUC2 gene with more extensive deletions to -223 bp or more lost its response to glucose derepression; 2) Each part of GAL10-SUC2 promoter combination acted almost independently. All of the combinations showed no apparent coordinated promoter function under our experimental conditions; 3) Sequences between -89bp and -41bp of SUC2 upstream region are responsible for constitutive expression of nonglycosylated invertase. The two tracts of poly (dA-dT) of this region may serve as promoter elements.SummaryThe plasmid series YEP5 1 Δ n bearing GAL10-SUC2 promoter combinations were constructed by inserting SUC2 gene with different upstream deletions downstream GAL10 promoter on YEP5 1. After transforming yeast cells S. cerevisiae, the invertases expressed by eacn of the transformants were measured and analysed by means of PAGE. The results showed that: 1) The SUC2 gene with upstream deletion to at -636bp expressed high level glycosylated form of invertase under glucose derepression, while SUC2 gene with more extensive deletions to -223 bp or more lost its response to glucose derepression; 2) Each part of GAL10-SUC2 promoter combination acted almost independently. All of the combinations showed no apparent coordinated promoter function under our experimental conditions; 3) Sequences between -89bp and -41bp of SUC2 upstream region are responsible for constitutive expression of nonglycosylated invertase. The two tracts of poly (dA-dT) of this region may serve as promoter elements.

Effect of insulin on the expression of interleukin 2 receptor

SummaryIn this paper, we report our work about the effect of insulin on the expression of interleukin 2 receptor (IL-2R). Our experiments showed that insulin was not T cell growth factor, but was able to augment the expression of IL-2R during T cell activation by PHA and to delay the decline rate of IL-2R+ cell. As a result, the percentage of IL-2R+ cells significantly increased during and after activation. Furthermore, insulin was capable of enhancing the production of interleukin 1 by macrophage and interleukin 2 by T lymphocyte. Based on these results, we suggest that there are at least two related mechanisms involved in the augmentation of the expression of IL-2R on activated T cells, i.e., direct action of insulin on T cells and indirect action of insulin by enhancing the production of interleukin l.

Mitogenic factor for T inducer/helper cells in Entamoeba histolytica extracts

SummaryIn order to investigate mitogenic effect of Entamoeba histolytica extracts (EHE) on T cell subpopulations, monoclonal antibodies of the OKT system were used to separate T inducer/helper (OKT4+) and T suppressor/cytotoxic (OKT8+) cells. Only OKT4+ cells were found to respond to EHE stimulation as indicated by incorporation of3HTdR into cultured cells. Determination of interleukin-2 (IL-2) activities revealed that the response of OKT4+ cells to EHE was due to the action of IL-2.

An experimental study on membrane malignant phenotype of tumour cells and their reversion

SummaryA human promyelocytic leukemic cell line (HL-60 cells) was induced to differentiate along the myeloid pathway in vitro by 1. 25% dimethylsulfoxide (DMSO) as an inducer. The membrane fluidity, the quantity of ConA binding sites on the cell membrane surface, and the protein tyrosine kinase (Tyr-PK) activity existing in NP-40 membrane extract and cytoplasma extract were determined respectively. The activity of tumour-derived immunosuppressive factor (TDSF) secreted by HL-60 cells into culture suppernatant was also determined. The results demonstrated that: (1) HL-60 cells were capable of undergoing differentiation onto the myeloid pathway in the presence of DMSO. The growth of DMSO-treated HL-60 cells became slow and synthesis rate of DNA decreased by about 50%. (2) Both membrane fluidity and the quantity of ConA binding sites on membrane were obviously lower after induced with DMSO than those before induction. (3) The Tyr-PK activity in the NP-40 membrane extract incresed during the period of induced differentiation. The phosphorylation level of endogenous protein in cytoplasma. extract decreased with the process of induced differentiation. It may be reasoned that the phosphatase activity is much higher than the phosphorylase activity. (4) The secretive level of TDSF by HL-60 cells during the period of induced differentiation revealed no change. The preliminary results showed that the malignant phenotypes of tumour cells we used may undergo reversible changes with induced differentiation of tumour cells except the secretion of TDSF.

Effect of tumor-derived immunosuppressive factor(s) on interleukin 2 and on expression of interleukin 2 receptor

SummaryIn this paper, we have described the effects of tumor-derived immunosuppressive factor(s) (TDSF,) on interleukin 2 (IL-2) production, on IL-2 responsiveness and on the expression of IL-2 receptors. The results showed that TDSF was able to markedly inhibit the production of IL-2 from PHA-stimulated lymphocytes and IL-2-dependent proliferation of activated lymphocytes, and to partially inhibit the expression of IL-2 receptor. These results suggest that inhibiting IL-2 production and responsiveness may be a major mechanism by which TDSF inhibit T lymphocyte proliferation and other immune responses. That TDSF exerted a very potent inhibiting action on IL-2 responsiveness is especially noticeable if we consider using IL-2 as an immunotherapeudic agent. This may be an important reason why treatment of tumor with IL-2 did not yield satisfactory results so far.

Effect of immunosuppressive factor produced by human lung cancer cell line A549 on the production and action of interleukin 1.

SummaryA549, a human lung cancer cell line, spontaneously produces a tumor-derived immunosuppressive factor (TDSF) which inhibits the production and action of interleukin 1 (IL-1). After exposure of macrophages to TDSF for 5 h, the production of IL-1 by macrophages was significantly inhibited. The inhibition was much stronger if TDSF existed continuously in macrophage culture. The response of thymocytes treated with nylon wool to exogenous IL-1 was significantly suppressed in the presence of TDSF, suggesting that TDSF can inhibit the action of IL-1. The thymocytes untreated with nylon wool could proliferate after being stimulated with Con A. The proliferation was significantly suppressed by TDSF in a dose-dependent manner. These results suggest that the inhibitory action of TDSF on T cell activation is associated with IL-1, and that TDSF might exert an inhibitory action on other reactions mediated by IL-1. Furthermore, TDSF can reduce the supplementation of new T cells by inhibiting the proliferation of thymocytes.

Investigation on the inhibitory effect of tumor-derived immunosuppressive factor (s) on T lymphocyte proliferation

SummaryUsing five tumor cell lines, the effect of tumor-derived immunosuppressive factor(s) (TDSF) on T lymphocyte proliferation and its mechanism have been investigated. It was found that TDSF markedly inhibited PHA-stimulated T lymphocyte proliferation via a noncytotoxic mechanism. The inhibition increased in dose-dependent manner and the maximum inhibition was achieved when the factor was added at the initiation of the culture. When PBMC were preincubated with supernatants of tumor cells for 24 h, washed extensively and then cocultured with freshly prepared PBMC, similar suppressive effects were observed. The above results indicated that the activation of any suppressor cell subgroup may be one of the mechanisms of immunosuppressive action of TDSF.

Effect of insulin on the production and action of interleukin 1

SummaryThe effect of insulin on the production and action of interleukin 1 (IL-1) was investigated in this study. After being treated with nylon wool to remove adherent cells, the thymocytes showed only a weak response to Con A in the abscence of exogenous IL-1, and this response could not be influenced by insulin. Insulin was able to significantly enhance the response of thymocytes to Con A if the thymocytes were not pre-treated with nylon wool, and it was able to significantly enhance the response of the thymocytes treated with nylon wool to Con A in the presence of exogenous IL-1. It has been demonstrated that insulin could augment the production of IL-1 by macrophages stimulated by LPS. These results suggest that the regulating action of insulin on T cell activation is associated with macrophages or IL-1, and insulin might exert a regulating role on other reactions mediated by IL-1. Furthermore, our results demonstrated that the action of active insulin could be weakened by the presence of inactive insulin.

Studies on hypokalemic flabbiness disease

SummaryThe new disease entity, hypokalemic flabbiness, is an endemic and epidemic hypokalemic paralytic disease found in recent twenty years mainly in certain rural districts in China where cotton is produced. We have carried out extensive investigations and deep-going research work on it for more than ten years. The following preliminary conclusions were drawn: (1) This disease does not belong to the group of well known hypokalemic paralysis of different origins (such as hypokalemic periodic paralysis and Cohn’s disease, etc.). It refers to a new clinical entity which was first discovered and described in China. Up to the present it has not yet been reported in medical literature abroad. (2) Its etiology is very closely related to the gossypol in the raw cotton seed oil usually taken by the inhabitants living in the endemic areas. (3) Pathologically and pathophysiologically, there are evidences of renal tubular damage and renal tubular acidosis, and the loss of body potassium is via kidney. Allergic reaction may presumably take part in the pathogenesis of this disease.