Gaye Erten

Relationship between CD107a expression and cytotoxic activity

NK cells play important roles in innate immunity against tumors and infections of the host. Studies show that CD107a (LAMP-1) may be a marker for degranulation of NK and activated CD8+ T cells. In our study, the relationship between the expression of CD107a, cytokine secretion and cytotoxic activity in CD56+ NK, CD8+ T cells and lymphocytes has been determined after various stimuli. Effector cells from PBMCs of healthy subjects were isolated and K562 cell line was used as target of cytotoxicity. IL-2 stimulation resulted in a significant increase of CD107a expression in CD56+ NK, CD8+ T cells and lymphocytes. Increased expression of CD107a after IL-2 stimulation of NK cells was parallel to the increase of cytotoxicity. Our results suggest that CD107a expression may be a sensitive marker for the cytotoxic activity determination.

Regulatory NK Cells Suppress Antigen-Specific T Cell Responses

The immune system has a variety of regulatory/suppressive processes, which are decisive for the development of a healthy or an allergic immune response to allergens. NK1 and NK2 subsets have been demonstrated to display counterregulatory and provocative roles in immune responses, similar to Th1 and Th2 cells. T regulatory cells suppressing both Th1 and Th2 responses have been the focus of intensive research during the last decade. In this study, we aimed to investigate regulatory NK cells in humans, by characterization of NK cell subsets according to their IL-10 secretion property. Freshly purified IL-10-secreting NK cells expressed up to 40-fold increase in IL-10, but not in the FoxP3 and TGF-β mRNAs. PHA and IL-2 stimulation as well as vitamin D3/dexamethasone and anti-CD2/CD16 mAbs are demonstrated to induce IL-10 expression in NK cells. The effect of IL-10+ NK cells on Ag-specific T cell proliferation has been examined in bee venom major allergen, phospholipase A2- and purified protein derivative of Mycobecterium bovis-induced T cell proliferation. IL-10+ NK cells significantly suppressed both allergen/Ag-induced T cell proliferation and secretion of IL-13 and IFN-γ, particularly due to secreted IL-10 as demonstrated by blocking of the IL-10 receptor. These results demonstrate that a distinct small fraction of NK cells display regulatory functions in humans.

Osteoprotegerin/RANKL Axis and Progression of Coronary Artery Calcification in Hemodialysis Patients

BACKGROUND AND OBJECTIVES Vascular calcification is associated with increased cardiovascular mortality in chronic hemodialysis patients. This prospective study investigated the relationship between serum osteoprotegerin, receptor activator of NF-κB ligand, inflammatory markers, and progression of coronary artery calcification score. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS Seventy-eight hemodialysis patients were enrolled. Serum IL-1β, IL-6, TNF-α, osteoprotegerin, receptor activator of NF-κB, fetuin A, and bone alkaline phosphatase were measured by ELISA. Coronary artery calcification score was measured two times with 1-year intervals, and patients were classified as progressive or nonprogressive. RESULTS Baseline and first-year serum osteoprotegerin levels were significantly higher in the progressive than nonprogressive group (17.39±9.67 versus 12.90±6.59 pmol/L, P=0.02; 35.17±18.35 versus 24±11.65 pmol/L, P=0.002, respectively). The ratio of serum osteoprotegerin to receptor activator of NF-κB ligand at 1 year was significantly higher in the progressive group (0.26 [0.15-0.46] versus 0.18 [0.12-0.28], P=0.004). Serum osteoprotegerin levels were significantly correlated with coronary artery calcification score at both baseline (r=0.36, P=0.001) and 1 year (r=0.36, P=0.001). Importantly, progression in coronary artery calcification score significantly correlated with change in serum osteoprotegerin levels (r=0.39, P=0.001). In addition, serum receptor activator of NF-κB ligand levels were significantly inversely correlated with coronary artery calcification scores at both baseline (r=-0.29, P=0.01) and 1 year (r=-0.29, P=0.001). In linear regression analysis for predicting coronary artery calcification score progression, only baseline coronary artery calcification score and change in osteoprotegerin were retained as significant factors in the model. CONCLUSIONS Baseline coronary artery calcification score and serum osteoprotegerin levels were significantly associated with progression of coronary artery calcification score in hemodialysis patients.

Natural Killer Cells in Allergic Inflammation

Natural killer (NK) cells are large granular lymphocytes of the innate immune system that exert a potent function against infected and tumor cells. Although NK cells were originally defined by their capacity to lyse target cells and produce interferon-gamma without prior activation, recent studies showed that NK cells also display a potent regulatory function. They are activated or inhibited through the ligation of germline-encoded receptors and are involved in mediating cytotoxicity, producing cytokines and providing costimulation to cells of the adaptive immune system. NK cells play important roles in viral infections, autoimmunity, pregnancy, cancer and bone marrow transplantation, but little is known about the role of NK cells in allergy. Recent developments in the understanding of the role of human NK cells in allergy are overviewed.

Natural killer cells: versatile roles in autoimmune and infectious diseases

Natural killer (NK) cells are essential members of innate immunity and they rapidly respond to a variety of insults via cytokine secretion and cytolytic activity. Effector functions of NK cells form an important first line of innate immunity against viral, bacterial and parasitic infections, as well as an important bridge for the activation of adaptive immune responses. The control of NK-cell activation and killing is now understood to be a highly complex system of diverse inhibitory and activatory receptor–ligand interactions, sensing changes in MHC expression. NK cells have a functional role in innate immunity as the primary source of NK-cell-derived immunoregulatory cytokines, which have been identified in target organs of patients suffering from autoimmune diseases, and play a critical role in early defense against infectious agents. This review focuses on recent research of NK cells, summarizing their potential immunoregulatory role in modulating autoimmunity and infectious diseases.

Synergistic growth inhibitory effect of deracoxib with doxorubicin against a canine mammary tumor cell line, CMT-U27.

Cyclooxygenase (COX) inhibitors have been shown to exert anti-angiogenic and anti-tumor activities on many types of malignant tumors. These anticancer properties make it worthwhile to examine the possible benefit of combining COX inhibitors with other anti-cancer agents. In the present study, we evaluated the potential of deracoxib (DER) in potentiating antitumor activity of doxorubicin (DOX) in canine mammary carcinoma cells (CMT-U27). DER (50–250 µM) enhanced the antiproliferative activity of DOX by reducing the IC50 (approximately 3- to 3.5 fold). Interaction analysis of the data showed that combinations of DOX at 0.9 µM with DER (100–250 µM) produced synergism in the CMT-U27 cell line, with a ratio index ranging from 1.98 to 2.33. In additional studies identifying the mechanism of observed synergistic effect, we found that DER strongly potentiated DOX-caused G0/G1 arrest in cell cycle progression. Also, DER (100–250 µM) augmented apoptosis induction with approximately 1.35- and 1.37- fold increases in apoptotic response caused by DOX in the cells. DER enhanced the antiproliferative effect of DOX in conjunction with induction of apoptosis by modulation of Bcl-2 expression and changes in the cell cycle of the CMT-U27 cell line. Although the exact molecular mechanism of the alterations in the cell cycle and apoptosis observed with DER and DOX combinations require further investigations, the results suggest that the synergistic effect of DOX and DER combinations in CMT therapy may be achieved at relatively lower doses of DOX with lesser side effects. Therefore, combining DER with DOX may prove beneficial in the clinical treatment of canine mammary cancer.

The Effects of Piroxicam and Deracoxib on Canine Mammary Tumour Cell Line

Cyclooxygenase (COX) inhibitors, already widely used for the treatment of pain and inflammation, are considered as promising compounds for the prevention and treatment of neoplasia. The aim of our study was to determine the direct antiproliferative effects of nonsteroidal anti-inflammatory drugs (NSAIDs), piroxicam and deracoxib, at a variety of concentrations as both single and combined treatments on canine mammary carcinoma cell line CMT-U27 and to understand the mechanisms of cell death. MTT assay was performed to determine cell viability, and flow cytometric analyses were performed to evaluate apoptosis and cell cycle alterations. Significant decrease in cell viability was observed at high concentrations of piroxicam and deracoxib in both single and combined treatments after 72 h incubation. Combined treatment produced a significantly greater inhibition than that caused by either agent alone. Also apoptotic cell number was increased by both drugs at the cytotoxic concentrations. However, concomitant treatment of cells with piroxicam and deracoxib resulted in significant induction of apoptosis at lower concentrations and accumulation of cells in the G0/G1 phase. Significant cytotoxic effects exhibited by the combination of piroxicam and deracoxib against canine mammary carcinoma cells in vitro suggest an attractive approach for the treatment of canine mammary carcinoma.

Differences in lymphocyte subpopulation count and function in cord, maternal and adult blood.

OBJECTIVE Phenotypical characterization and functional activity of lymphocytes and natural killer (NK) cells in cord blood (CB) were investigated, and maternal peripheral blood (MPB) values were compared to those of adult peripheral blood (APB) (control). METHODS To determine cytotoxic activity target cells (K562) were labeled with carboxyfluorescein diacetate (CFDA) or fluorescein isothiocyanate (FITC), and propidium iodide (PI) was used to label dead cells. Cell surface expression in CB, APB, and MPB cells were analyzed using flow cytometry. RESULTS CB and MPB mononuclear cells had similar CD45, CD34, CD4, and surface molecule for T helper cell expression, but had low-level expression of total T-lymphocyte surface molecules CD3 and CD8. CD19 and HLA-DR expression was higher in CB than in MPB. The same high-level of expression for CD19 and HLA-DR was observed in APB, as compared to MPB. All other cell surface expressions were similar in APB and MPB samples. NK (CD16+ and CD56+) cells in CB was similar to that in MPB and APB, and the level of inhibitory KIR receptors in NK cells was higher in venous CB than in MPB and APB. The only difference between MPB and APB was that the CD158a level was higher in MPB. No difference was observed in NK cells in CB and MPB, in terms of cytotoxicity. CONCLUSION The present results show that there was numerical and proportional variability of lymphocytes and their subgroups in CB and APB, but no cytological difference.