The effect of interleukin-15 on the expression of killer-cell immunoglobulin-like receptors on peripheral natural killer cells in human

Hepatocytes and IL-15: a favorable microenvironment for T cell survival and CD8+ T cell differentiation

Human intrahepatic lymphocytes are enriched in CD1d-unrestricted T cells coexpressing NKR. Although the origin of this population remains controversial, it is possible to speculate that the hepatic microenvironment, namely epithelial cells or the cytokine milieu, may play a role in its shaping. IL-15 is constitutively expressed in the liver and has a key role in activation and survival of innate and tissue-associated immune cells. In this in vitro study, we examined whether hepatocyte cell lines and/or IL-15 could play a role in the generation of NK-like T cells. The results show that both HepG2 cells and a human immortalized hepatocyte cell line increase survival and drive basal proliferation of T cells. In addition, IL-15 was capable of inducing Ag-independent up-regulation of NKR, including NKG2A, Ig-like receptors, and de novo expression of CD56 and NKp46 in CD8(+)CD56(-) T cells. In conclusion, our study suggests that hepatocytes and IL-15 create a favorable microenvironment for T cells to growth and survive. It can be proposed that the increased percentage of intrahepatic nonclassical NKT cells could be in part due to a local CD8(+) T cell differentiation.

Patient survival by Hsp70 membrane phenotype: association with different routes of metastasis

BACKGROUND

Heat shock proteins (HSPs) play important roles in tumor immunity. The authors prospectively investigated the correlation between the tumor-specific Hsp70 membrane expression as an independent clinicopathological marker and overall survival in tumor entities that differ in their route of metastasis.

METHODS

Hsp70 membrane expression was examined by flow cytometry in 58 colon, 19 gastric, 54 lower rectal carcinoma, and 19 squamous cell carcinoma specimens and the corresponding normal tissues at time of first diagnosis. Kaplan-Meier survival curves were analyzed to determine the relation of Hsp70 expression to the patients' prognosis.

RESULTS

An Hsp70 membrane-positive phenotype was found in 40% (colon), 37% (gastric), 43% (lower rectal), and 42% (squamous cell) of the analyzed tumor specimens. None of the corresponding normal tissues was found to be Hsp70 membrane-positive. In patients with colon (P = .032) and gastric (P = .045) carcinomas, an Hsp70 membrane expression correlated significantly with an improved overall survival; a negative association was seen in lower rectal (P = .085) and squamous cell carcinoma (P = .048).

CONCLUSIONS

The authors hypothesized that differing relations between surface expression of Hsp70 on tumor cells and clinical outcomes may reflect differences in the route of metastases. Colon and gastric carcinomas metastasize into the liver where hepatic natural killer cells may have the capacity to recognize and kill Hsp70 membrane-positive tumor cells and thus account for a better overall survival.

Low expression of CD161 and NKG2D activating NK receptor is associated with impaired NK cell cytotoxicity in metastatic melanoma patients

Natural killer (NK) cells play a role in the innate and adaptive antitumor immune responses. The activity of NK cells is regulated by functionally opposing, activating and inhibitory receptors whose balance ultimately determines whether target cells will be susceptible to NK cell mediated lysis. As melanoma is an immunogenic tumor, the effect of immunomodulating agents is consistently investigated. In this study in 79 metastatic melanoma (MM) patients and 52 controls NK activity, expression of activating NKG2D and CD161 receptors and KIR receptors, CD158a and CD158b, on freshly isolated PBL and NK cells were evaluated. Native NK cell activity of melanoma patients in clinical stage I-III and MM patients was determined against NK sensitive K562, NK resistant Daudi, human melanoma FemX, HeLa and HL 60 target tumor cell lines. In addition, predictive pretherapy immunomodulating effect after 18 h in vitro treatments of PBL of MM patients with rh IL-2, IFN-alpha (IFN), 13-cis retinoic acid (RA) and combination IFN-alpha and RA was evaluated with respect to NK cell lyses against K562 and FemX cell lines. In this study we show for the first time that low expression of CD161 and activating NKG2D receptors, without increased expression of KIR receptors CD158a and CD158b, as well as a decrease in the cytotoxic, CD16(bright) NK cell subset, is associated with a significant impairment in NK cell activity in MM patients. Furthermore, the predictive pretherapy finding that IL-2, IFN, IFN and RA, unlike RA alone, can enhance NK cell activity of MM patients against FemX melanoma tumor cell line can be of help in the design and development of therapeutic regimens, considering that it has recently been shown that low-dose combination of different immunomodulators represents the most promising approach in the therapy of MM.

Natural killer cells: primary target for hepatitis C virus immune evasion strategies?

Liver cirrhosis and hepatocellular carcinoma secondary to chronic hepatitis C virus (HCV) infection requiring transplantation represents a significant public health problem. The most remarkable feature of hepatitis C virus is the ability to establish chronic infection in the vast majority of cases. Efforts to define clinical correlates of HCV persistence have focused primarily on CD4 and CD8 T cell responses. Until recently, the role of innate immunity in determining the outcome of HCV infection had received relatively little attention. Natural killer (NK) cells are an important antiviral effector population eliminating virus through direct killing and cytokine production. Recent studies highlighting the cross-talk between NK cells, dendritic cells (DCs) and T cells have prompted reevaluation of the important role NK cells play in regulating and maintaining specific immune responses. Like many other viruses, HCV has evolved strategies to evade detection and elimination by NK cells. T cell defects observed in HCV infection may be a consequence of inhibition of NK:DC interactions. We propose a theoretical model for HCV persistence that places the NK cell at the center of HCV immune evasion strategies. While this model is only theoretical, it provides a plausible interpretation of many published observations and a useful working model to test the role of NK cells in HCV persistence. In conclusion, the role of innate immune cells and their regulation of antigen-specific responses by the initial innate response to the virus, in particular NK cells, may prove to be an informative and clinically relevant avenue of investigation.

The effect of Juzen-taiho-to/TJ-48 on the expression of killer-cell immunoglobulin-like receptors (CD158a/b) on peripheral lymphocytes in vitro experiment

Juzen-taiho-to (TJ-48), a mixture of extracts from 10 medicinal herbs, has been used traditionally to treat patients with anemia, anorexia or fatigue. It is well known that the treatment of TJ-48 result in the decrease of patient's complaints, as well as the increase of NK cytolytic activity (NK activity) although its augmentation is not clear in the other kampo formula from the clinical viewpoint. To investigate its biological activities, such as the augmentation of NK activity, we analyzed the effects of TJ-48 on the expression of killer-cell immunoglobulin-like receptors (KIRs) in vitro experiment. The peripheral lymphocytes were incubated in medium alone, or medium containing TJ-48 or interleukin-2 (IL-2) plus TJ-48 at several concentrations for 48 h. After each incubation, cells were collected and their KIRs were detected by flow cytometry using monoclonal antibodies CD158a and CD158b. TJ-48 increased the populations of CD16+CD158a+ and CD16+CD158b+ cells in a dose-dependent manner. In contrast, CD16-CD158a/b+ cells did not increase. Additionally, the extract of TJ-48 enhanced the increase of KIRs expression induced by IL-2. These actions contribute to the augmentation of NK cytolytic activity by TJ-48, and might explain, in part, its antitumor effects which has been observed in vivo.

Hepatic interleuklin 15 (IL-15) expression: implications for local NK/NKT cell homeostasis and development

Interleukin 15 (IL-15) is critical for the development of human and murine natural killer (NK) cells and hepatic-derived NK T cells (NKT) in mice, and for the homeostatic maintenance of NK/NKT and CD8(+) memory T cells. The lymphocyte repertoire of an adult human liver includes significant populations of NK and NKT-like cells, which may arise locally from hepatic haematopoietic stem cells (HSCs). We investigated hepatic IL-15 levels and the expression of IL-2/IL-15-receptor beta-chain (IL-2/IL-15Rbeta; CD122) on mature hepatic lymphocytes and HSCs. Reverse transcription-polymerase chain reaction (RT-PCR) was used to detect secreted/intracellular IL-15 transcripts. IL-15 protein was localized using immunohistochemistry; levels were measured by enzyme-linked immunosorbent assay IL-2/IL-15Rbeta expression by flow-cytometry. Normal hepatic IL-15 protein was detected at 0.43 ng/100 mg total protein (n = 11, range 0.10 ng-0.9 ng). There was a significant increase in HCV-infected tissue (1.78 ng, P < 0.005, n = 11, range 0.18-2.43 ng). The staining pattern suggests that infiltrating monocytes and tissue resident Kupffer cells are the main producers. IL-15 protein was detected in supernatants from cultured liver biopsy specimens in the absence of stimulation (mean 175.8 pg/100 mg wet tissue, n = 3), which increased significantly upon stimulation (P < 0.05, mean 231.21 pg). On average, 61% of hepatic HSCs expressed IL-2/IL-15Rbeta suggesting a local lymphopoietic role. Eighty per cent of NK and 45.8% of CD56(+) T cells expressed IL-2/IL-15Rbeta, suggesting involvement in local CD56(+) cell activation and expansion. Constitutive expression of IL-15 protein and IL-2/IL-15Rbeta on hepatic lymphocytes suggests a key role in the generation and maintenance of the unique hepatic lymphoid repertoire. The significant increase observed in HCV-infected liver suggests a role for IL-15 in host antiviral responses in the liver.