Interleukin-18 synergism with interleukin-2 in cytotoxicity and NKG2D expression of human natural killer cells.

Natural killer (NK) cells play an important role in anti-tumor immunity. Interleukin (IL)-18 is an immunoregulatory cytokine that induces potent NK cell-dependent anti-tumor responses when administrated with other cytokines. In this study, we explored the effects of combining IL-18 and IL-2 on NK cytotoxicity as well as expression levels of the NK cell receptor NKG2D in vitro. Freshly isolated PBMCs were incubated for 48 h with IL-18 and IL-2, then CD107a expression on CD3-CD56+ NK cells was determined by three-colour flow cytometry to evaluate the cytotoxicity of NK cells against human erythroleukemia K562 cells and human colon carcinoma HT29 cells. Flow cytometric analysis was also employed to determine NKG2D expression on NK cells. The combined use of IL-18 and IL-2 significantly increased CD107a expression on NK cells compared with using IL-18 or IL-2 alone, suggesting that the combination of these two cytokines exerted synergistic enhancement of NK cytotoxicity. IL-18 also enhanced NKG2D expression on NK cells when administered with IL-2. In addition, blockade of NKG2D signaling with NKG2D-blocking antibody attenuated the up-regulatory effect of combining IL-18 and IL-2 on NK cytolysis. Our data revealed that IL-18 synergized with IL-2 to dramatically enhance the cytolytic activity of human NK cells in a NKG2D-dependent manner. The results appear encouraging for the use of combined IL-18 and IL-2 in tumor immunotherapy.

Peripheral Foxp3+ regulatory T cells and natural killer group 2, member D expression levels in natural killer cells of patients with colorectal cancer.

Foxp3+ regulatory T cells (Tregs) and natural killer group 2, member D (NKG2D)-positive natural killer (NK) cells are considered to be important in the immune escape of colorectal cancer (CRC). However, the association between these two variables remains obscure. Therefore, in the present study, the levels of peripheral Tregs and NKG2D expression in NK cells and the associations in CRC patients were investigated. A total of 35 CRC patients and 16 healthy controls were enrolled in this study. Flow cytometry was performed to assay Treg numbers and NKG2D expression levels in NK cells in peripheral blood samples. Serum carcino-embryonic antigen (CEA) protein was assayed by electrochemiluminescence. Peripheral Treg numbers were significantly increased (P<0.05), while NKG2D expression levels in NK cells were significantly reduced (P<0.01) in CRC patients compared with healthy controls. However, no significant differences were identified in Treg numbers between CRC patients with and without lymph node metastases and between CRC patients with different clinical stages of CRC. Similarly, no significant differences were detected in NKG2D expression levels in NK cells between the different patient groups. Statistical analysis revealed that increased Treg numbers were not correlated with reduced NKG2D expression levels in NK cells from CRC patients. In addition, no statistical correlation was observed between Treg numbers and serum CEA protein in CRC patients. In conclusion, the upregulation of Tregs was not significantly correlated with the downregulation of NKG2D expression in NK cells in peripheral blood from CRC patients.

Purification of hydroxyanthraquinones and cinnamic acid from the roots of Rheum officinale Baill.

A chromatographic method for isolation and purification of chemical constituents from the well-known traditional Chinese drug Da-huang (roots of Rheum officinale Baill.) was established by using 12% cross-linked agarose gel, Superose 12, as the separation media. A two-step separation procedure is employed. Sixty five percent methanol was used as the eluent for separation of cinnamic acid, rhein, physcion and emodin form Da-huang crude extract. The fraction containing aloe-emodin and chrysophanol was then separated by using 55% methanol containing 0.5% acetic acid as the eluent. As a result, cinnamic acid and five kinds of hydroxyanthraquinones including rhein, aloe-emodin, chrysophanol, physcion and emodin were obtained. The retention behavior of hydroxyanthraquinones on Superose 12 was also studied. The retention of hydroxyanthraquinones on Superose 12 is based on a mixture of hydrogen bonding and hydrophobic interactions between the hydroxyl groups of the hydroxyanthraquinones and the residues of the cross-linking reagents used in the manufacturing process of Superose 12.

Isolation and purification of chemical constituents from the pericarp of Sophora japonica L. by chromatography on a 12% cross-linked agarose gel.

A chromatographic method using 12% cross-linked agarose gel Superose 12 as the separation medium was developed for isolation and purification of the chemical constituents from the pericarp of Sophora japonica L. The mobile phase used for the separation was 2% acetic acid and 7% acetic acid in gradient elution. As a result, eight compounds including four kinds of flavonoids and four kinds of isoflavonoids were obtained in a one-step separation. A straightforward explanation of the separation mechanism of flavonoids and isoflavonoids on Superose 12 is also given. The flavonoids and isoflavonoids are retained on Superose 12 by a combination of hydrogen bonding and hydrophobic interactions between the hydroxyl groups of aglycone and the residues of the cross-linking reagents used in the manufacture of Superose 12.

Isolation and purification of flavonoid and isoflavonoid compounds from the pericarp of Sophora japonica L. by adsorption chromatography on 12% cross-linked agarose gel media.

A method for isolation and purification of flavonoid and isoflavonoid compounds in extracts of the pericarp of Sophora japonica L. was established by adsorption chromatography on the 12% cross-linked agarose gel Superose 12. The crude extracts were pre-separated to two parts, sample A and sample B, on a D-101 macroporous resin column by elution with 20% ethanol and 40% ethanol, respectively. Samples A and B were then separated by adsorption chromatography on Superose 12 with 40% methanol as the mobile phase. Eight compounds including four kinds of flavonoids and four kinds of isoflavonoids were obtained by the proposed method. The adsorption mechanisms of flavonoids and isoflavonoids on Superose 12 were also discussed.