Suppression Of Natural Killer Activity Research Articles

Acute portal hypertension using portal vein ligation abrogates TRAIL expression of liver-resident NK cells.

The effects of acute portal hypertension (PHT), which is reported as poor prognostic factors in patients with hepatocellular carcinoma, are not well known on the liver immune system, including natural killer (NK) cells. The aim of this study, therefore, was to investigate how acute PHT influences the functions and characteristics of liver‐resident NK (lr‐NK) cells using an acute PHT mouse model. Acute PHT decreased the number of tumor necrosis factor–related apoptosis‐inducing ligand (TRAIL+) lr‐NK cells by about 20% and attenuated cytotoxic activity against the Hepa1‐6 cell line by about 40%. Among various cytokine, only interleukin‐33 (IL‐33), which inhibits NK activity, significantly increased after portal vein ligation (PVL). Because lr‐NK cells highly expressed ST2/IL‐33R, IL‐33 co‐culture significantly suppressed TRAIL expression on lr‐NK cells by about 50%, and IL‐33 administration markedly decreased TRAIL expression and cytotoxic activity of lr‐NK cells. Furthermore, the TRAIL+ NK cells population was maintained by anti‐IL33 antibody or following portosystemic shunt procedure even after PVL. Finally, we demonstrated that IL‐33 decreased TRAIL expression in lr‐NK cells via AKT–forkhead box O (FoxO) and mitogen‐activated protein kinase (MAPK) signaling. Conclusion: This work demonstrates that PHT suppresses the TRAIL+ lr‐NK cell population and antitumor activities in the liver. Additionally, Akt‐FoxO and MAPK signaling pathways attenuate the TRAIL expression in lt‐NK cells via IL‐33 receptor in mice.

Monocytes inhibit NK activity via TGF-β in patients with obstructive sleep apnoea.

Obstructive sleep apnoea (OSA) is associated with cancer incidence and mortality. The contribution of the immune system appears to be crucial; however, the potential role of monocytes and natural killer (NK) cells remains unclear.Quantitative reverse transcriptase PCR, flow cytometry and in vitro assays were used to analyse the phenotype and immune response activity in 92 patients with OSA (60 recently diagnosed untreated patients and 32 patients after 6 months of treatment with continuous positive airway pressure (CPAP)) and 29 healthy volunteers (HV).We determined that monocytes in patients with OSA exhibit an immunosuppressive phenotype, including surface expression of glycoprotein-A repetitions predominant protein (GARP) and transforming growth factor-β (TGF-β), in contrast to those from the HV and CPAP groups. High levels of TGF-β were detected in OSA sera. TGF-β release by GARP+ monocytes impaired NK cytotoxicity and maturation. This altered phenotype correlated with the hypoxic severity clinical score (CT90). Reoxygenation eventually restored the altered phenotypes and cytotoxicity.This study demonstrates that GARP+ monocytes from untreated patients with OSA have an NK-suppressing role through their release of TGF-β. Our findings show that monocyte plasticity immunomodulates NK activity in this pathology, suggesting a potential role in cancer incidence.

The Breast Cancer-Associated Glycoforms of MUC1, MUC1-Tn and sialyl-Tn, Are Expressed in COSMC Wild-Type Cells and Bind the C-Type Lectin MGL.

Aberrant glycosylation occurs in the majority of human cancers and changes in mucin-type O-glycosylation are key events that play a role in the induction of invasion and metastases. These changes generate novel cancer-specific glyco-antigens that can interact with cells of the immune system through carbohydrate binding lectins. Two glyco-epitopes that are found expressed by many carcinomas are Tn (GalNAc-Ser/Thr) and STn (NeuAcα2,6GalNAc-Ser/Thr). These glycans can be carried on many mucin-type glycoproteins including MUC1. We show that the majority of breast cancers carry Tn within the same cell and in close proximity to extended glycan T (Galβ1,3GalNAc) the addition of Gal to the GalNAc being catalysed by the T synthase. The presence of active T synthase suggests that loss of the private chaperone for T synthase, COSMC, does not explain the expression of Tn and STn in breast cancer cells. We show that MUC1 carrying both Tn or STn can bind to the C-type lectin MGL and using atomic force microscopy show that they bind to MGL with a similar deadadhesion force. Tumour associated STn is associated with poor prognosis and resistance to chemotherapy in breast carcinomas, inhibition of DC maturation, DC apoptosis and inhibition of NK activity. As engagement of MGL in the absence of TLR triggering may lead to anergy, the binding of MUC1-STn to MGL may be in part responsible for some of the characteristics of STn expressing tumours.

Abstract 1670: Collagen matrix deposition by hepatic stellate cells protects hepatocellular carcinoma from NK-mediated cytotoxicity

Abstract Up to 90% of hepatocellular carcinoma (HCC) cases are preceded by chronic liver disease and cirrhosis in which the major histopathologic feature is hepatic fibrosis (HF), or the excessive accumulation collagen fibers in the liver stroma. These fibers are deposited by activated hepatic stellate cells (hSTEL) in response to hepatitis infection, and alcohol liver disease (ALD). Both HF and subsequent HCC are associated with local and systemic suppression of natural killer (NK) cells, which normally serve to clear over-activated hSTELL and de novo HCC. While NK dysfunction has been studied independently in HF and HCC, neither field has considered a common mechanism caused by changes in the local microenvironment. Cells interact with collagen through a subset of integrins, or one of four known receptors that possess either activating or inhibitory function. One of these receptors, known as leukocyte-associated immunoglobulin-like receptor 1 (LAIR-1), contains an immunotyrosine-based inhibitory motif (ITIM), elicits inhibitory signaling in lymphocytes, and is highly expressed on NK cells. We observed increased expression of LAIR-1 on dividing primary human NK cells, and found that bioartifical collagen matrix significantly inhibits NK proliferation in a dose-dependent manner in response to IL-2. In contrast, NK cells isolated from LAIR-1 germline knockout mice displayed near complete resistance to collagen-induced suppression in similar proliferation assays. This led us to hypothesize that the accumulation of hSTEL-derived collagen directly inhibits NK activity and protects both hSTEL and HCC from innate clearance. We demonstrate that the deposition of native collagen matrix by hSTELs imparts a significant protective effect from subsequent NK lysis in standard 51Cr-release cytotoxicity assays. A HCC cell line (HEPG2), which produces no collagen in the absence of hSTELs, is susceptible to activated NK killing and is unaffected by collagenase. To test if hSTEL-derived collagen cross-protects bystander HEPG2 cells, we developed a novel flow cytometry-based duel-target cytotoxicity assay capable of measuring the simultaneous killing of multiple targets. Primary hSTEL and HEPG2 cells were pre-labeled with different lipophilic dyes and co-cultured for 72h, resulting in an accurate analogue of the HCC microenvironment including HEPG2 nodules, interstitial hSTEL, and a complex intersecting network of fibrillar collagen. Using this co-culture system, we show that hSTEL-derive collagen matrix protects both hSTEL and HEPG2 targets from NK cytotoxicity. Pretreatment of the co-culture system with collagenase removes the protective collagen matrix and restores NK cytotoxicity. These results suggest that hSTEL-derived collagen may contribute to NK dysfunction in LF and HCC, and identifies LAIR-1 as a potential mediator of collagen-induced immune suppression. Citation Format: Adam W. Mailloux, Pearlie K Epling-Burnette. Collagen matrix deposition by hepatic stellate cells protects hepatocellular carcinoma from NK-mediated cytotoxicity. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1670. doi:10.1158/1538-7445.AM2014-1670

Suppression of NK cell-mediated cytotoxicity against PRRSV-infected porcine alveolar macrophages in vitro

The adaptive immunity against PRRSV has already been studied in depth, but only limited data are available on the innate immune responses against this pathogen. In the present study, we analyzed the interaction between porcine natural killer (NK) cells and PRRSV-infected primary porcine alveolar macrophages (PAMs), since NK cells are one of the most important components of innate immunity and PAMs are primary target cells of PRRSV infection. NK cytotoxicity assays were performed using enriched NK cells as effector cells and virus-infected or mock-inoculated PAMs as target cells. The NK cytotoxicity against PRRSV-infected PAMs was decreased starting from 6h post inoculation (hpi) till the end of the experiment (12 hpi) and was significantly lower than that against pseudorabies virus (PrV)-infected PAMs. UV-inactivated PRRSV also suppressed NK activity, but much less than infectious PRRSV. Furthermore, co-incubation with PRRSV-infected PAMs inhibited degranulation of NK cells. Finally, using the supernatant of PRRSV-infected PAMs collected at 12 hpi showed that the suppressive effect of PRRSV on NK cytotoxicity was not mediated by soluble factors. In conclusion, PRRSV-infected PAMs showed a reduced susceptibility toward NK cytotoxicity, which may represent one of the multiple evasion strategies of PRRSV.

Second thoughts on the role of glucocorticoids in the in vivo suppression of NK activity following stress

Second thoughts on the role of glucocorticoids in the in vivo suppression of NK activity following stress

CD39/ENTPD1 Expression by CD4 +Foxp3 + Regulatory T Cells Promotes Hepatic Metastatic Tumor Growth in Mice

Adenosine mediates immune suppression and is generated by the ectonucleotidases CD39 (ENTPD1) and CD73 that are expressed on vascular endothelial cells and regulatory T cells (Tregs). Although tumor-infiltrating immune cells include Foxp3(+) Tregs, it is not clear whether local adenosine generation by Tregs promotes tumor growth in a CD39-dependent manner. In this study, we have examined the effect of CD39 expression by Tregs on effector immune cell responses to hepatic metastases in vivo. A model of hepatic metastatic cancer was developed with portal vein infusion of luciferase-expressing melanoma B16/F10 cells and MCA38 colon cancer cells in wild-type (wt) and mutant mice null for Cd39. Chimeric mice were generated by bone marrow transplantation (BMT) using Cd39 null or wt C57BL6 donors and irradiated recipient mice. We demonstrate that hepatic growth of melanoma metastatic tumors was strongly inhibited in mice with Cd39 null vasculature or in wt mice with circulating Cd39 null bone marrow-derived cells. We show functional CD39 expression on CD4(+)Foxp3(+) Tregs suppressed antitumor immunity mediated by natural killer (NK) cells in vitro and in vivo. Finally, inhibition of CD39 activity by polyoxometalate-1, a pharmacologic inhibitor of nucleoside triphosphate diphosphohydrolase activity, significantly inhibited tumor growth (P < .001). CD39 expression on Tregs inhibits NK activity and is permissive for metastatic growth. Pharmacologic or targeted inhibition of CD39 enzymatic activity may find utility as an adjunct therapy for secondary hepatic malignancies.

Enhancement of natural killer cell activity of aged mice by modified arabinoxylan rice bran (MGN-3/Biobran)

The present study is aimed to examine the possibility of enhancement of natural killer (NK) cell activity in aged C57BL/6 and C3H mice using MGN-3, a modified arabinoxylan from rice bran. Intraperitoneal injection of MGN-3 (10 mg kg(-1) per day) caused a remarkable increase in the peritoneal NK activity as early as 2 days (35.2 lytic units), and the level remained elevated through day 14. The control aged mice had a level of 5.8 lytic units. Enhancement in NK activity was associated with an increase in both the binding capacity of NK cells to tumour targets and in the granular content as measured by BLT-esterase activity. Treatment did not alter the percentage of peritoneal NK cells. Data showed that peritoneal macrophages inhibit NK activity. In conclusion, MGN-3 enhances murine NK activity of aged mice and may be useful for enhancing NK function in aged humans.

Improvement of deficient natural killer activity and delayed bactericidal activity by a thiol proteinase inhibitor, E-64-d, in leukocytes from Chediak–Higashi syndrome patients in vitro

We previously reported that administration of a potent calpain inhibitor, E-64-d, which protects protein kinase C (PKC) from proteolysis, in a mouse model of Chediak–Higashi syndrome (CHS) (beige mice), decreases its susceptibility to Staphylococcus aureus infection. In the present study, we examined the in vitro effect of E-64-d on both deficient natural killer (NK) and delayed bactericidal activities of leukocytes from six CHS patients. Our results showed that pretreatment of peripheral blood mononuclear cells (PBMCs) obtained from CHS patients with E-64-d (1 μg/ml) significantly enhanced NK activity against K562 cells. The delayed bactericidal activity of polymorphonuclear cells (PMNs) against S. aureus also showed marked improvement. This was recovered to almost normal levels when PMNs were pretreated with E-64-d (1 μg/ml). On the other hand, the same concentration of E-64-d did not affect either the NK or bactericidal activity of normal controls. In addition, we confirmed that following E-64-d treatment, the abnormal down-regulation of PKC activity after concanavalin A (Con A) stimulation was eliminated in PBMCs obtained from CHS patients. To examine whether PKC is involved in the NK cell-mediated cytolysis and bactericidal activity of PMNs, two potent PKC inhibitors, chelerythrin and GÖ6976, were used. We found that chelerythrin inhibits NK activity of normal PBMCs in a dose-dependent manner, and GÖ6976 inhibits NK activity at doses that inhibit Ca 2+-dependent PKC isozymes. These inhibitors also suppressed the bactericidal activity of PMNs against S. aureus. Taken together, our findings suggested that E-64-d improved the compromised NK and bactericidal activity of leukocytes from CHS patients by reversing the down-regulation of PKC activity.

DDVP markedly decreases the expression of granzyme B and granzyme 3/K in human NK cells

Natural killer (NK), lymphokine-activated killer (LAK), and cytotoxic T lymphocyte (CTL) cells kill target cells by the directed release of cytolytic granules that contain perforin, granzymes, and granulysin. We have found previously that dimethyl 2,2-dichlorovinyl phosphate (DDVP, dichlorvos), an organophosphorus pesticide, significantly decreased the expression of perforin, granzyme A (GrA), and granulysin and inhibited NK, LAK, and CTL activities. To further explore the mechanism of organophosphorus pesticide-induced inhibition of cell-mediated cytolysis, we examined whether organophosphorus pesticides affect the expression of GrB and Gr3/K in NK cells. We used an interleukin-2 (IL-2) independent human NK cell line, NK-92CI. We confirmed that NK-92CI cells express intracellular GrB and Gr3/K by flow cytometry, that NK-92CI cells are highly cytotoxic to K562 cells with a chromium release assay, and that DDVP significantly inhibited cytolytic activity of NK-92CI cells in a dose- and time-dependent manner. We found that DDVP significantly decreased the expression of GrB and Gr3/K in NK-92CI cells in a dose- and time-dependent manner by flow cytometry. Immunocytochemical results showed that DDVP significantly decreases the level of GrB positive granules in NK-92CI cells, which may be due to degranulation. Taken together, DDVP significantly inhibits NK activity and reduces the intracellular GrB and Gr3/K levels in NK cells.

Is intravenous immunoglobulins (IVIG) efficacious in early pregnancy failure? A critical review and meta-analysis for patients who fail in vitro fertilization and embryo transfer (IVF)

Intravenous Immunoglobulins (IVIG) are widely used off label in the treatment of early reproductive failure. As IVIG is expensive, and may have side-effects, evidence of efficacy is needed. Previous results have suggested that the pre-conception treatment of primary recurrent abortion patients might be effective, but the data set has been too small for adequate statistical power. More recently it has been suggested that IVIG may improve the success rate of in vitro fertilization and embryo transfer (IVF) in patients with prior IVF failures, but clinical trials have given conflicting results that need explanation. Systematic reviews generating inconclusive results have focused on methodological rigor to the exclusion of biological plausibility. Review of current basic science of design, measurement, and evaluation of clinical trials and basic science mechanisms providing a rationale for treatment. Meta-analysis of published randomized controlled and cohort-controlled trials (updated with two unpublished data sets) evaluating IVIG treatment in IVF failure patients. Live birth rate was used as the most relevant endpoint. The ability of different sources of IVIG to suppress natural killer (NK) cell activity was determined using a standard (51)Cr-release assay in vitro. Meta-analysis of three published randomized controlled trials (RCTs) of IVIG in IVF failure patients shows a significant increase in the live birth rate per woman (p = 0.012; Number Needed to Treat for 1 additional live birth, NNT = 6.0 women). Using live birth rate per embryo transferred, and adding data from two cohort-controlled trials to the meta-analysis further supports this conclusion (overall p = 0.000015, NNT = 3.7 women). Relevant variables appear to include properties and scheduling of the IVIG, and selection of patients with abnormal immune test results. Different IVIG preparations vary significantly in their ability to suppress NK activity in vitro. A rationale for use of IVIG is provided by a review of mechanisms of IVIG action and mechanisms underlying failure of chromosomally normal embryos.

Prostaglandin e(2) suppresses NK activity in vivo and promotes postoperative tumor metastasis in rats.

Prostaglandins (PGs) were shown in vitro to suppress several functions of cellular immunity. It is unclear, however, whether physiological levels of PGs can suppress cellular immunity in vivo and whether such suppression would compromise postoperative host resistance to metastasis. Fischer 344 rats were administered PGE(2) in doses (18 to 300 micro g/kg subcutaneously) that increased the serum levels approximately 2- to 4-fold. We then assessed the number and activity of circulating natural killer (NK) cells, as well as rats' resistance to experimental metastasis of a syngeneic NK-sensitive tumor (MADB106). To study whether endogenously released PGs after surgery compromise these indices, we tested whether laparotomy adversely affects them and whether a cyclooxygenase-synthesis inhibitor, indomethacin (4 mg/kg), attenuates these effects. PGE(2) dose-dependently suppressed NK activity per NK cell and dose-dependently increased 4- and 24-hour MADB106 lung tumor retention (LTR); 240 micro g/kg of PGE(2) quadrupled the number of lung metastases counted 3 weeks later. Selective depletion of NK cells abrogated the promotion of LTR by PGE(2). Surgery significantly suppressed NK activity and increased MADB106 LTR, and indomethacin halved these effects without affecting nonoperated rats. PGE(2) is a potent in vivo suppressor of NK activity, and its postoperative release may promote tumor recurrence.

Indomethacin attenuates the immunosuppressive and tumor-promoting effects of surgery

Abstract: We have previously shown in rats that both intrathecal and systemic analgesia regimens attenuate surgery-induced increases in tumor susceptibility. The current study used indomethacin to assess the role of prostaglandins and inflammation-associated pain in mediating the deleterious effects of surgery on immunity and tumor susceptibility. Male and female Fischer 344 rats were anesthetized with halothane and were either subjected or not to experimental laparotomy, followed by the administration of indomethacin or vehicle. Tumor susceptibility was assessed by the lung retention assay using the syngeneic MADB106 mammary adenocarcinoma cell line, a natural killer (NK)-sensitive tumor that colonizes only in the lungs. Surgery resulted in a 2- to 3.5-fold increase in lung tumor retention, and indomethacin administration significantly reduced this effect in both sexes without affecting unoperated animals. Indomethacin also attenuated the reductions in rearing behavior evident after surgery, suggesting that it relieved abdominal discomfort. Surgery increased interleukin-6 levels and suppressed NK activity per milliliter blood. Indomethacin restored NK activity in both male and female rats but attenuated surgery-induced interleukin-6 increases only in the male rats. These findings further support our previous work implicating pain in mediating the tumor-enhancing effects of surgery and implicate prostaglandins in mediating this effect. If similar relationships occur in humans, controlling postoperative pain and inflammation must become a priority in the management of cancer patients undergoing surgery. © 2002 by the American Pain Society

Renal carcinoma cell lines inhibit natural killer activity via the CD94 receptor molecule.

MHC class I molecules protect normal and transformed cells from lysis by natural killer (NK) cells through recognition of receptors expressed on leucocytes. Defects in NK cell activity and lymphokine activated killer (LAK) cell generation have been previously demonstrated in patients with renal cell carcinoma (RCC). However, to date, the importance of NK receptor/MHC class I interactions for immune evasion by RCC cells has not been described. In this study, human RCC cell lines (HTB46, HTB47, ACHN, CRL 1933 and HTB44) were found to be susceptible to lysis by both NK cells and interleukin-15 (IL-15)-derived LAK cells from normal donors in vitro. However, when NK cells were co-cultured with RCC cells their expression of the CD94 NK receptor molecule was significantly increased and their cytolytic activity against RCC targets was reduced. The cytolytic activity of NK cells was restored by the addition of IL-15, which further augmented the expression of CD94 on CD56+ NK cells. Disruption of NK receptor-MHC class I interactions by the addition of blocking antibodies to CD94 had no effect on the lysis of K562 or HTB47 targets by NK cells. However, the sensitivity of HTB46 cells to NK-mediated lysis was increased by blocking the CD94 receptor molecule, but only when the NK cells had not been previously co-cultured with RCC cells. This was independent of the presence of IL-15. These results show that RCC cells can inhibit NK activity via CD94 and suggest that disruption of interactions between receptor and ligand on RCC cells in vivo may augment the immune response against tumours by innate effector cells.

Evidence that postoperative pain is a mediator of the tumor-promoting effects of surgery in rats

We have previously shown in rats that the provision of analgesic doses of morphine significantly reduces the tumor-promoting effects of undergoing and recovering from surgery. Because morphine had no effect in non-operated animals, and because a single preoperative dose given hours before tumor inoculation was effective, we have suggested that it is the pain-relieving effects of the drug that underlies its beneficial impact. To support and strengthen this suggestion, two different regimens of analgesia were employed, the systemic administration of the more selective μ-agonist, fentanyl, and the intrathecal (i.t.) administration of bupivacaine plus morphine. To assess host resistance against metastasis, we used a lung clearance assay of the MADB106 mammary adenocarcinoma, a natural killer (NK)-sensitive syngeneic cell line that metastasizes only to the lungs. Female and male Fischer 344 rats were randomly assigned to one of four groups using a 2×2 experimental design: experimental laparotomy under halothane anesthesia versus anesthesia alone, by drug treatment versus vehicle. In the first in vivo experiment, fentanyl was administered 20 min before surgery (40 μg/kg subcutaneously (s.c.)), and at the end of surgery in a slow-release suspension (20 μg/kg s.c.). In the second in vivo experiment, bupivacaine (10 μg) plus morphine (20 μg) in 50 μl was administered i.t. before surgery. Surgery resulted in a 3- to 4-fold increase in the lung retention of MADB106 cells in both males and females, and the observed surgery-induced increase in lung tumor retention was reduced by more than 65% in the fentanyl-treated animals and more than 45% in the animals receiving i.t. bupivacaine plus morphine. Neither drug regimen exerted effects in the anesthesia only animals. Surgery also resulted in a significant suppression of whole blood NK activity assessed at 5 h postoperatively, the same time point at which MADB106 tumor cells were inoculated in the in vivo studies. Unlike the in vivo study, fentanyl suppressed NK activity at this time point in non-operated rats, but had no effect in operated rats. Taken together, these findings strengthen the suggestion that the management of perioperative pain is a critical factor in preventing surgery-induced decreases in host resistance against metastasis. If similar relationships between pain and metastasis occur in humans, then pain control must become a priority in the postoperative care of individuals with cancer.

Stress, immune regulation, and immunity: applications for asthma.

The neuroendocrine mediators reach the cells of the immune system either through the peripheral circulation or through direct innervation of lymphoid organs. Primary and secondary lymphoid organs are innervated by sympathetic nerve fibers. Lymphocytes and monocytes express receptors for several stress hormones, including CRH, ACTH, cortisol, norepinephrine, and epinephrine. Therefore, it is reasonable to conclude that the neuroendocrine hormones released during a stressful event could alter immune function and subsequently alter the course of immune-based diseases. The impact of psychological stress on immune function has been the subject of extensive research efforts. Using a variety of models from largely healthy humans undergoing various forms of natural and experimental stress models, stress has been associated with suppression of NK activity, mitogen- and antigen-induced lymphocyte proliferation and in vitro production of IL-2 and IFN-gamma. Psychological stress is also associated with a higher rate of in vivo hypoergy to common recall-delayed type hypersensitivity antigens. These studies have suggested that psychological stress suppresses various components of CMI responses. Also, data suggest that chronic stress does not simply suppress the immune system, but induces a shift in the type-1/type-2 cytokine balance toward a predominant type-2 cytokine response. Such a change would favor the inflammatory milieu characteristic of asthma and allergic diseases. Recent studies using well-controlled teenage asthmatic subjects demonstrated immunological changes (decreased NK cell cytotoxicity and cytokine alterations) in response to exam stress. These immune alterations are consistent with a cytokine milieu that could potentially worsen asthma. However, there were no changes in peak flow rates, self-report asthma symptoms, or medication use. The lack of correlation between stress and asthma symptoms may have been related to the timing of the visits in relation to the stressor, the duration of the stressor, disease severity, or a lack of accurate self-report data. Alternatively, stress-mediated exacerbations of asthma may require multiple alterations by stress, including cytokine dysregulation or vagal-mediated airway hyperresponsiveness. The rationale for stress management in asthma is based upon the notion that stress causes a change in immune balance that would favor asthma activity in susceptible individuals. This immune imbalance can be found in TH1/TH2 cytokine changes that occur with stress. Although it has not yet been demonstrated that stress can cause or directly influence the development of asthma, it is interesting to note that both the incidence and prevalence of asthma continue to increase and are higher in urban than in rural areas. Among other differences is the well-appreciated higher chronic stress levels associated with urban living.

Relative involvement of cannabinoid CB 1 and CB 2 receptors in the Δ9-tetrahydrocannabinol-induced inhibition of natural killer activity

We demonstrated that in vivo administration of Δ 9-tetrahydrocannabinol in mice (15 mg/kg s.c.) significantly inhibited natural killer cell (NK) cytolytic activity without affecting Concanavalin A (ConA)-induced splenocyte proliferation. Moreover, we investigated the effect of in vivo pretreatment with cannabinoid receptor antagonists, namely, the selective cannabinoid CB 1 receptor antagonist SR 141716 [ N-piperidin-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-3-pyrazolecarboxamide] and the selective cannabinoid CB 2 receptor antagonist SR 144528 { N-[(1 S)-endo-1,3,3-trimethyl bicyclo [2.2.1] heptan-2-yl]-5-(4-chloro-3-methylphenyl)-1-(4-methylbenzyl)-pyrazole-3-carboxamide}, on Δ 9-tetrahydrocannabinol-induced inhibition of NK cytolytic activity. Both antagonists partially reversed the Δ 9-tetrahydrocannabinol inhibition of NK cytolytic activity, although the cannabinoid CB 1 receptor antagonist was more effective than the cannabinoid CB 2 receptor antagonist. The parallel measurement of interferon γ and interleukin 2 levels revealed that Δ 9-tetrahydrocannabinol significantly reduced (about 70%) the former cytokine without affecting the latter. Cannabinoid CB 1 and CB 2 receptor antagonists completely reversed the interferon γ reduction induced by Δ 9-tetrahydrocannabinol. Our results indicate that both types of cannabinoid receptors are involved in the complex network mediating NK cytolytic activity.

Progesterone-induced blocking factor inhibits degranulation of natural killer cells.

During the first trimester of pregnancy, nonclassical (CD3-, CD56+, CD16-, perforin [P]bright+) natural killer (NK) cells comprise the major decidual lymphocyte population. These cells, in spite of their high perforin content, exert a low cytolytic activity. Peripheral blood lymphocytes of healthy pregnant women produce progesterone-induced blocking factor (PIBF), which inhibits NK activity. PIBF-producing cells are likely to be present in decidua and might contribute to low decidual NK activity. Decidual cells obtained from elective pregnancy termination were double labeled for CD56 and PIBF. We tested the effect of PIBF on perforin liberation by activated peripheral blood NK cells. Sixty percent of decidual lymphocytes were CD56 + and expressed PIBF at the same time. PIBF-treated and untreated peripheral blood NK cells were incubated with K-562 cells, and perforin content of target conjugated NK cells was detected with immunocytochemistry. PIBF treatment of peripheral blood lymphocytes significantly reduced lysis of K-562 cells. Among target bound lymphocytes in PIBF-treated samples, we found a significantly (P < 0.01) higher rate of P+ cells than in untreated samples. These data suggest that PIBF inhibits cytotoxicity of NK cells via a block of degranulation, and since decidual NK cells are PIBF+, it cannot be ruled out that this effect of PIBF contributes to low decidual NK activity.

The role of gamma/delta T cells in progesterone-mediated immunomodulation during pregnancy: a review.

To determine if pregnancy is recognized by the immune system and if inadequate recognition of fetal antigens might result in failed pregnancy. Review of literature and current data. In the decidua gamma/delta TCR positive cells significantly increase in number. A subset of gamma/delta T cells reacts with nonpolymorphic Class I or Class I like molecules. Trophoblast recognition is mediated by the V gamma 1 subset which recognize a conserved mammalian sequence on the trophoblast. Almost all gamma/delta T cells in the decidua are activated and use the V delta 1 chain, whereas the majority of human peripheral gamma/delta lymphocytes expresses V gamma 9/V delta 2 TCR. Peripheral gamma/delta T cells of healthy pregnant women preferentially use V gamma V delta 1 chains, on the other hand, those of recurrent aborters use the V gamma 9V delta 2 combination. Signaling via the V gamma 1.4V delta 1 receptor induces a Th2 type response, whereas activation of the lymphocytes via the V gamma 9V delta 2 receptor results in increased IL-12 production and natural killer (NK) activity. In the presence of progesterone, activated lymphocytes synthesize the progesterone induced blocking factor (PIBF), which inhibits NK activity and exerts an anti abortive effect in vivo. Decidual CD56+ and gamma delta+ cells are to a high extent the same population. All decidual CD56+ cells express PIBF, thus it cannot be excluded that local production of this substance contributes to low decidual NK activity and thus to the success of the pregnancy.

N-acetylcysteine improves cytotoxic activity of cirrhotic rat liver-associated mononuclear cells.

Liver cirrhosis, which is associated with decreased plasma and hepatic glutathione (GSH), has been reported to cause the suppression of NK activity in peripheral blood mononuclear cells. Since low GSH levels in lymphocytes are known to alter lymphocyte function, we examined the correlation between intracellular GSH levels and the cytotoxic activity of liver-associated mononuclear cells (liver MNC). We show here that rat liver contains a highly active population of NK cells (CD3- NKR-P1 + cells) that kill Yac-1 in vitro and that the cytotoxic activity of this NK population is directly proportional to liver MNC GSH. This proportionality is independent of the methods used to alter GSH level. Thus, in vitro treatment of liver MNC with buthionine sulfoximine to lower GSH levels lowers the cytotoxic activity. MNC from cirrhotic liver, in which implanted tumor cells grow faster, have both low GSH levels and low cytotoxicity, and supplementation of cirrhotic liver MNC with N-acetylcysteine raises GSH levels and increases cytotoxicity. These findings suggest a physiologic mechanism, i.e. decreased GSH, may be causally associated with the increased incidence of hepatoma in cirrhotic individuals and the increased growth of hepatoma cells in cirrhotic animals. Thus, we suggest that the GSH is important to the optimal functioning of the hepatic immunity that protects against hepatoma development.