Decreased expression of CD69 in chronic fatigue syndrome in relation to inflammatory markers: evidence for a severe disorder in the early activation of T lymphocytes and natural killer cells

There is some evidence that patients with chronic fatigue syndrome (CFS) suffer from immune abnormalities, such as immune activation and decreased immune cell responsivity upon polyclonal stimili. This study was designed to evaluate lymphocyte activation in CFS by using a CD69 expression assay. CD69 acts as a costimulatory molecule for T- and natural killer (NK) cell activation. We collected whole blood from CFS patients, who met CDC criteria, and healthy volunteers. The blood samples were stimulated with mitogens during 18 h and the levels of activated T and NK cells expressing CD69 were measured on a Coulter Epics flow cytometer using a three color immunofluorescence staining protocol. The expression of the CD69 activation marker on T cells (CD3+, CD3+CD4+, and CD3+CD8+) and on NK cells (CD45+CD56+) was significantly lower in CFS patients than in healthy subjects. These differences were significant to the extent that a significant diagnostic performance was obtained, i.e. the area under the ROC curve was around 89%. No differences either in the number of leukocytes or in the number or percentage of lymphocytes, i.e. CD3, CD4, CD8 and CD19, could be found between CFS patients and the controls. Patients with CFS show defects in T- and NK cell activation. Since induction of CD69 surface expression is dependent on the activation of the protein kinase C (PKC) activation pathway, it is suggested that in CFS there is a disorder in the early activation of the immune system involving PKC.     

Different sensitivity to interleukin 4 of interleukin 2- and interferon alpha-induced CD69 antigen expression in human resting NK cells and CD3+, CD4-, CD8- lymphocytes.

The effect of rIL-4 on CD69 antigen expression induced by rIL-2 or by rINF-alpha on human resting NK cells and CD3+, CD4-, CD8- T lymphocytes has been investigated. rIL-4 drastically inhibited CD69 antigen expression induced by rIL-2 in both cell types. In contrast, rIL-4 did not alter rINF-alpha-induced CD69 antigen expression. Consistent results were obtained evaluating the cytolytic activity of NK cells against the Raji target cell line: rINF-alpha-induced lytic activity was not inhibited by rIL-4, while rIL-2-induced lytic activity was drastically inhibited. Proliferative activity of NK cells induced by rIL-2, in contrast, was only slightly reduced by rIL-4. rIL-4 did not alter the expression of the beta chain of IL-2 receptor, evaluated in NK cells by indirect immunofluorescence. Expression of the alpha chain of IL-2 receptor could not be detected in NK cells by indirect immunofluorescence. It can therefore be suggested that the selective inhibitory effect of rIL-4 on rIL-2-induced activation of NK cells is not mediated by downregulation of alpha and beta chains of IL-2 receptor.     

Effects of leptin and ghrelin on the expression of membrane molecules and cytokine production by NK cells from the peripheral blood

The influence of leptin and ghrelin, as well as their combined effects, on the expression of membrane molecules and cytokine production by NK cells from peripheral blood was studied in vitro. The effects of hormones were assayed at the concentrations corresponding to their peripheral blood levels in the course of physiological pregnancy. It was established that the investigated hormones exerted significant effects only at the concentrations typical of the II–III trimester of pregnancy. In particular, leptin and ghrelin and their combination increased the number of CD56^brightNKp46⁺NK cells in the suspension of mononuclear cells and inhibited the expression of homing molecules CCR7 and inhibitor molecules LILRB in NKp46⁺NK cells. Leptin and its combination with ghrelin increased the expression of L-selectin in CD56^brightNKp46⁺NK cells but inhibited the secretion of IL-10 by NKp46⁺NK cells. Leptin reduced the production of IL-4 by NKp46⁺ cells, while ghrelin eliminated this effect. The hormones did not influence the expression of inhibitory molecules NKG2A in NKp46⁺ cells and the production of TGF-β1, IL-17A, and IFN-γ by these cells. Thus, the investigated hormones at the concentrations typical of the II–III trimester of pregnancy effectively regulate the expression of membrane molecules and cytokine production by NK cells of the peripheral blood.     

Monocyte-independent T-cell activation by polyclonal antithymocyte globulins.

The in vitro mitogenic properties of polyclonal antithymocyte and antilymphocyte globulins (ATG) on peripheral blood mononuclear cells were investigated. The ATG were mitogenic in a dose-dependent manner with maximal proliferation observed at 250 or 500 micrograms/ml. ATG activated blastogenesis of CD4+, CD8+, and CD57+ (NK cells) lymphocytes. The ATG induced interleukin-2 (IL-2) and interferon-gamma (IFN-gamma) gene expression and lymphokine secretion in cell culture supernatant and IL-2 receptor (CD25) expression. At submitogenic concentrations ATG potentialized the effect of phorbol esters on T cell proliferation, but not that of calcium ionophore. The mitogenic effect of ATG was not abrogated by monocyte depletion indicating that like CD2 monoclonal antibodies (mAbs) ATG activate T cells via a monocyte-independent pathway. CD3 and CD2 mAbs which activate T cells without binding to B surface determinants stimulated the proliferation of B cells and their differentiation into immunoglobulin (Ig)-secreting cells. In contrast, ATG induced only a transient B cell activation, but failed to support B cell differentiation into Ig-secreting cells despite the secretion of IL-2. These properties shared by ATG obtained in horses or rabbits by immunization with different cell types appear to differ from those of other T cell mitogens.     

Short-term and long-term leptin exposure differentially affect human natural killer cell immune functions

Epidemiological studies have indicated that obesity is associated with a higher risk for certain cancers caused by elevated levels of adipocyte-derived hormones. Leptin, one such hormone produced by adipocytes, is a major regulator of metabolism and has also been shown to modulate immunity. However, its role in regulating human natural killer (NK) cell functions is largely unknown. Here, we show that the leptin receptor (Ob-R) is expressed on 5% of NK cells isolated from blood donors, as measured with flow cytometry, and expression of the signal-transducing long form of the leptin receptor Ob-Rb was confirmed with quantitative PCR. The Ob-R+ subpopulation displayed a lower expression of CD16, a cell surface receptor mediating antibody-dependent activation. Short-term stimulation with leptin increased IFNγ secretion, CD69 activation marker expression, and cytotoxic lysis of tumor cells; this was mediated by an improved conjugate forming between NK cells and tumor cells as well as higher expression of tumor necrosis factor-related apoptosis-inducing ligand. On the contrary, long-term incubation with leptin significantly impaired these NK cell immune functions and decreased cell proliferation. In addition, phosphorylation of Jak-2 after leptin stimulation was reduced in peripheral mononuclear blood cells from obese humans compared with normal-weight controls. NK cells represent an immune cell population that is crucial for an effective antitumor response. Here, we show that long-term exposure to leptin, similarly to the situation in obese individuals with elevated serum leptin levels, significantly impairs integral parts of NK cell immune functions, possibly linking leptin to increased cancer susceptibility in obesity.     

Exercise-induced stress enhances mammary tumor growth in rats: beneficial effect of the hormone melatonin

We hypothesized that intense exercise training (forced swimming for 30 min, 5 days/week) may enhance the progression of mammary carcinogenesis through the involvement of stress hormones, such as catecholamines and prolactin, which can promote breast cancer. After the appearance of the DMBA-induced tumors in Sprague-Dawley rats, the effect was evaluated of exercise-induced stress (with or without administration of the hormone melatonin) on the survival time, tumor multiplicity, and tumor growth until the death of the animals. In a second set of experiments, after one month of exercise, the NK cells count in blood, and the plasma concentrations of catecholamines and prolactin were determined. Although no significant change was found in either the survival time of the rats or the tumor multiplicity, exercise significantly increased the tumor growth rate. Stress was confirmed by the enhanced adrenaline and prolactin concentrations in the blood of the exercised rats. Exercise-induced stress did not change the percentage of NK cells in the tumor-bearing rats. Melatonin counteracted the increased tumor growth, returning the prolactin and adrenaline concentrations to their optimal physiological levels in the exercised tumor-bearing rats, thus confirming an “anti-stress” role of this hormone. In conclusion, intense exercise-induced stress enhances mammary carcinogenesis through the involvement of adrenaline and prolactin. The results also confirmed a role of melatonin as a therapeutic aid against breast cancer in general, and in particular during situations of stress.     

Primary immune responses by cord blood CD4(+) T cells and NK cells inhibit Epstein-Barr virus B-cell transformation in vitro

Epstein-Barr virus (EBV) transformation of B cells from fetal cord blood in vitro varies depending on the individual sample. When a single preparation of EBV was simultaneously used to transform fetal cord blood samples from six different individuals, the virus transformation titer varied from less than zero to 10(5.9). We show that this variation in EBV transformation is associated with a marked primary immune response in cord blood samples predominately involving CD4(+) T cells and CD16(+) CD56(+) NK cells. After virus challenge both CD4(+) T cells and NK cells in fetal cord blood cultures expressed the lymphocyte activation marker CD69. The cytotoxic response against autologous EBV-infected lymphoblastoid cell line (LCL) targets correlated with the number of CD16(+) CD69(+) cells and was inversely correlated with the virus transformation titer. Although NK activity was detected in fresh cord blood and increased following activation by the virus, killing of autologous LCLs was detected only following activation by exposure to the virus. Both activated CD4(+) T cells and CD16(+) NK cells were independently able to kill autologous LCLs. Both interleukin-2 and gamma interferon were produced by CD4(+) T cells after virus challenge. The titer of EBV was lower when purified B cells were used than when whole cord blood was used. Addition of monocytes restored the virus titer, while addition of resting T cells or EBV-activated CD4(+) T-cell blasts reduced the virus titer. We conclude that there are primary NK-cell and Th1-type CD4(+) T-cell responses to EBV in fetal cord blood that limit the expansion of EBV-infected cells and in some cases eliminate virus infection in vitro.     

CD16 cross-linking induces increased expression of CD56 and production of IL-12 in peripheral NK cells

Human NK cells are classified into two populations according to the intensity of CD56 surface expression, as well as possession of CD16, FcRIII. CD56^dimCD16^bright make up 90% circulating NK cells, whereas CD56^brightCD16^-/dim comprises the remaining 10%. Here we report that peripheral NK cells upon CD16 cross-linking up-regulates the expression of activating markers and receptors such as CD25, CD69, NKp44, NKp30, CD40L and the intensity of CD56 expression. Additionally, co-culturing immature DCs with CD16 activated NK cells was found to significantly increase the expression of maturation markers on DCs. These results suggest that CD16 cross-linking on resting peripheral blood NK cells triggers the activation of these cells and induces the appearance of CD56^bright NK cells. The latter were found capable of producing pro-inflammatory cytokines, IFN-γ and TNF-α and notably IL-12.     

The CD16-/CD56bright subset of NK cells is resistant to oxidant-induced cell death

Phagocyte-derived reactive oxygen species ("oxygen radicals") have been ascribed a suppressive role in immunoregulation by inducing dysfunction and apoptotic cell death in lymphocytes. Earlier studies show that human NK cells are exceptionally sensitive to oxygen radical-induced apoptosis and functional inhibition. Two subsets of human CD56(+) NK cells have been identified: the highly cytotoxic CD56(dim) cells which constitute >90% of NK cells in peripheral blood, and the less cytotoxic but efficiently cytokine-producing CD56(bright) cells. In this study, we demonstrate that the CD56(bright) subset of NK cells, in contrast to CD56(dim) cells, remains viable and functionally intact after exposure to phagocyte-derived or exogenously added oxygen radicals. The resistance of CD56(bright) cells to oxidative stress was accompanied by a high capacity of neutralizing exogenous hydrogen peroxide, and by a high cell-surface expression of antioxidative thiols. Our results imply that CD56(bright) NK cells are endowed with an efficient antioxidative defense system that protects them from oxygen radical-induced inactivation.     

Recruitment of uterine NK cells: induction of CXC chemokine ligands 10 and 11 in human endometrium by estradiol and progesterone

Uterine NK (uNK) cells express a unique set of markers compared with blood NK cells. However, recent studies suggest that uNK cells may be derived from the recruitment of blood NK cells into the endometrium. In this study, we used an in vitro organ culture system to demonstrate that estradiol induces expression of chemokines CXCL10 and/or CXCL11 within human endometrium in 85% of patient samples tested. The average increase in gene expression after 10(-9) M estradiol treatment was 8.5-fold for CXCL10 and 7.7-fold for CXCL11 compared with medium alone. We observed that a specific estrogen receptor antagonist (ICI182780) was able to prevent chemokine gene induction, indicating that the effect of estradiol was receptor mediated. Moreover, our study showed that progesterone induced CXCL10 and CXCL11 expression in 83% of endometrial samples tested. We have also found that uNK cells and blood NK cells express the receptor for CXCL10 and CXCL11, CXCR3, with the highest expression found on uNK cells and CD56(bright) blood NK cells. These data indicate that sex hormones induce specific chemokines in nonpregnant human endometrium that can activate NK cell migration, and suggest that this mechanism may account for the increased NK cell numbers in endometrium during the menstrual cycle.     

Increased susceptibility to apoptosis of CD56dimCD16+ NK cells induces the enrichment of IFN-gamma-producing CD56bright cells in tuberculous pleurisy

Tuberculous pleuritis is a good model for the study of specific cells at the site of active Mycobacterium tuberculosis (Mtb) infection. We investigated the frequency and phenotype of NK cells in paired samples of peripheral blood and pleural fluid (PF) from patients with tuberculosis (TB) or parapneumonic infection. We demonstrated for the first time a reduction of NK cells in PF from TB with an enrichment in the CD56brightCD16- subset. In agreement, in PF NK cells we observed an increased expression of CD94, NKG2A, CD62L, and CCR7 molecules and lower expression of Bcl-2 and perforin. The activation markers CD69 and HLA-DR were also increased. The enrichment in the CD56bright subset was due to an increased susceptibility to apoptosis of CD56+CD16+ NK cells mediated by heat-labile and stable soluble factors present in tuberculous effusions and not in PF from other etiologies. Furthermore, in TB patients, Mtb-induced IFN-gamma production by PF NK cells was not dependent on the presence of CD3+, CD19+, and CD14+ cells, suggesting a direct interaction of CD56bright cells with Mtb and/or the involvement of other accessory cells present at the site of Mtb infection.     

Expansion of NK cells by engineered K562 cells co-expressing 4-1BBL and mMICA,combined with soluble IL-21

NK cells hold promise for protecting hosts from cancer and pathogen infection through direct killing and expressing immune-regulatory cytokines. In our study, a genetically modified K562 cell line with surface expression of 4-1BBL and MICA was constructed to expand functional NK cells in vitro for further adoptive immunotherapy against cancer. After a long-term up to 21 day co-culture with newly isolated peripheral blood mononuclear cells (PBMCs) in the presence of soluble IL-21 (sIL-21), notable increase in proportion of expanded NK cells was observed, especially the CD56^brightCD16⁺ subset. Apparent up-regulation of activating receptors CD38, CD69 and NKG2D was detected on expanded NK cells, so did inhibitory receptor CD94; the cytotoxicity of expanded NK cells against target tumor cells exceeded that of NK cells within fresh PBMCs. The intracellular staining showed expanded NK cells produced immune-regulatory IFN-γ. Taken together, we expanded NK cells with significant up-regulation of activating NKG2D and moderate enhancement of cytotoxicity, with IFN-γ producing ability and a more heterogeneous population of NK cells. These findings provide a novel perspective on expanding NK cells in vitro for further biology study and adoptive immunotherapy of NK cells against cancer.     

Lipoprotein lipase protects bovine endothelial cells from human NK cytotoxic activity

Human lipoprotein lipase (LPL), in a dose dependent fashion, significantly inhibited spontaneous human natural killer (NK) cells, but not lymphokine-activated killer (LAK) cytotoxic activity against bovine pulmonary endothelial cells. The effect was dependent on endothelial heparan sulfate (HS) sites, since heparitinase reverted it. When HS is added before LPL, NK and LAK cytotoxicity are markedly reduced. Endothelial and NK cell priming, with LPL and HS+LPL, significantly induced CD40 and CD154 expression, respectively. Furthermore, CD40 expression was inversely proportional to lytic units (R2 = 0.9, P < 0.001). Treating endothelial cells simultaneously with indomethacin, CD154 fusion protein, and Wortmanin prevented the CD40 effect increasing xenograft rejection. LPL and HS+LPL protect bovine endothelial cells from NK cytotoxicity by inducing CD40, CD154 expression, and secretion of soluble factors. The high, non-modulated expression of adhesion receptors and the low number of HS sites account for the minor effect of CD40 in LAK cytotoxic responses against bovine endothelial cells.     

Experimental studies on bacterial product cantastim derived from Pseudomonas aeruginosa. VII. Activation of immune cells of healthy controls and cancer patients

CANTASTIM (CS) is a purified extract of Pseudomonas aeruginosa with beneficial effects related to enhancing the immune responses in conditions such as chronic viral and bacterial infections, immunodeficiencies and cancer immunosuppression. The aim of this study was to determine the capacity of this biological product to stimulate in vitro human leukocytes in whole blood. Blood samples from healthy donors and cancer patients were incubated with CS for 24 h and leukocytes were assessed for induction of inflammatory cytokines (TNF-alpha and IL-1beta) by ELISA and expression of early activation marker CD69 by flow-cytometry. For both groups of investigated subjects, the levels of TNF-alpha and IL-1beta in the supernatants of whole blood culture stimulated with CS were significantly higher than in unstimulated cultures, although lower than in LPS-stimulated samples. Stimulation of whole blood cultures with CS increased both the frequency and the expression of CD69 on the surface of T lymphocytes and NK cells. Importantly, this was noticed not only for healthy controls, but also for cancer patients. These data demonstrate the capacity of bacterial immunomodulator CS to activate human leukocytes of healthy subjects and cancer patients.     

Rapid and potent induction of cell death and loss of NK cell cytotoxicity against oral tumors by F(ab′)2 fragment of anti-CD16 antibody

Freshly isolated untreated NK cells undergo rapid apoptosis and lose their cytotoxic function upon the addition of F(ab′)₂ fragment of anti-CD16 antibodies. Loss of NK cell cytotoxic function after treatment with F(ab′)₂ fragment of anti-CD16 antibody can be seen against K562 and UCLA-2 oral tumor cells when either added immediately in the co-cultures of NK cells with the tumor cells or after pre-treatment of NK cells with the antibody before their addition to the tumor cells. Addition of Interleukin-2 (IL-2) in combination with anti-CD16 antibody to NK cells delayed the induction of DNA fragmentation in NK cells, and even though decreased cytotoxicity could still be observed against K562 and UCLA-2 oral tumors when compared to IL-2 alone treated NK cells, the cytotoxicity levels remained relatively higher and approached those obtained by untreated NK cells in the absence of antibody treatment. No increases in IFN-γ, Granzymes A and B, Perforin and TRAIL genes could be seen in NK cells treated with anti-CD16 antibody. Neither secretion of IFN-γ nor increased expression of CD69 activation antigen could be observed after the treatment of NK cells with anti-CD16 antibody. Furthermore, IL-2 mediated increase in CD69 surface antigens was down-modulated by anti-CD16 antibody. Finally, the addition of anti-CD16 antibody to co-cultures of NK cells with tumor target cells was not inhibitory for the secretion of VEGF by oral tumor cells, unlike those co-cultured with untreated or IL-2 treated NK cells. Thus, binding and triggering of CD16 receptor on NK cells may enhance oral tumor survival and growth by decreased ability of NK cells to suppress VEGF secretion or induce tumor cell death during the interaction of NK cells with oral tumor cells. This work was supported by RO1-DE18830 from NIH.     

Influence of Naloxone on the cellular immune response to head-up tilt in humans

To evaluate a possible role for β-endorphin in the stress-induced modulation of natural killer (NK) cells, immunologically competent blood cells were followed in eight male volunteers administered either Naloxone or saline (control) during head-up tilt maintained until the appearance of presyncopal symptoms (PS). The PS appeared more rapidly with Naloxone compared to control [5.7 (SEM 1.1) vs 22.3 (SEM 5.1) min; P = 0.01]. The NK cell activity increased threefold during PS partly due to an increase in CD16⁺ and CD56⁺ NK cells in blood. In support, NK cell activity boosted with interferon-α and interleukin 2 rose in parallel with unboosted NK cell activity and NK cell concentration and activities returned to the baseline level after 105 min. The total lymphocyte count and the concentrations of CD3⁺, CD4⁺, CD8⁺, CD16⁺, and CD56⁺ cells increased during PS. Head-up tilt also induced an increase in plasma adrenaline concentration during control PS and a rise in plasma cortisol and adrenocorticotropic hormone concentrations up to 30 min thereafter, whereas no significant changes were found in plasma concentrations of noradrenaline, growth hormone, or β-endorphin. The results would indicate an influence of endorphin on the increase in plasma adrenaline concentration during head-up tilt and at the same time contra-indicate a significant role for adrenaline in the provocation of PS. The influence of head-up tilt on plasma β-endorphin was too small to influence the modulation of the cellular immune system. Accepted: 22 May 1997     

Influence of <Emphasis Type="Italic">Moringa oleifera</Emphasis> extract,vitamin C,and sodium bicarbonate on heat stress-induced HSP70 expression and cellular immune response in rabbits

The current study aimed to test the effect of Moringa oleifera extract (MOE), vitamin (Vit) C, and sodium bicarbonate (NaHCO₃) on heat stress (HS)-induced alterations in rabbits. Five groups of rabbits were designed as control, HS, HS?+?MOE, HS?+?Vit C, and HS?+?NaHCO₃. HS groups were exposed to high temperatures, while treatments were given in drinking water for 6 weeks. Levels of blood cortisol, leptin, IFN-γ, TNF-α, and IL-10 were assayed using ELISA, while adrenaline was assayed calorimetrically. Expression of HSP70, FOXP3, T cell receptor (TCR) γ, and δ mRNA was tested using real-time (RT)-PCR, while HSP70 protein expression was tested using western blotting in liver and kidney tissues. Infiltration of regulatory T cells (Treg; CD25⁺) and NK (CD56⁺) cells were tested using immunohistochemistry (IHC). The levels of liver enzymes (ALT & AST), urea, and creatinine were assayed calorimetrically, while body weight gain (BWG) and feed conversion ratio (FCR) were calculated. The results showed increased levels of cortisol, adrenaline, leptin, IFN-γ, TNF-α, ALT, AST, urea, and creatinine but decreased IL-10 in the HS group. Increased expression of HSP70 on both mRNA and protein levels was associated with increased NK and γδ T cells versus decreased Treg cell infiltration in liver and kidney tissues of the HS group. In the same group, BWG was decreased, while FCR was increased with respect to the control group. All treatments used in this study reversed the effects of HS significantly. In conclusion, MOE, Vit C, and NaHCO₃ can be added to rabbit diets for the amelioration of HS-induced symptoms.     

Gender effect on in vitro lymphocyte subset levels of healthy individuals

Differences in gender immune response have resulted in differences in immune protection and susceptibility to inflammatory diseases. Cultured peripheral blood mononuclear cells (PBMC) are widely used in immunomodulation studies, yet the influence of gender is usually not considered. We examined the effect of in vitro culture and phytohaemagglutinin (PHA) stimulation on PBMC lymphocyte subsets using flowcytometry. Full blood counts of whole blood showed higher levels of lymphocyte in male subjects. Lymphocyte subsets enumeration revealed higher NK cell counts in males and higher B cells in females. Cultured PBMC resulted in significant increases in B and total T cell percentages among females and NK cells among males. PHA stimulated significantly increased percentages of NK and total T cells in males and total activated T cells (CD69+) in females. Our results showed significant gender differences in lymphocyte subsets in cultured conditions. This may affect experimental outcome.     

Heterogeneous human NK cell responses to Plasmodium falciparum-infected erythrocytes

Human NK cells can respond rapidly to Plasmodium falciparum-infected RBC (iRBC) to produce IFN-gamma. In this study, we have examined the heterogeneity of this response among malaria-naive blood donors. Cells from all donors become partially activated (up-regulating CD69, perforin, and granzyme) upon exposure to iRBC but cells from only a subset of donors become fully activated (additionally up-regulating CD25, IFN-gamma, and surface expression of lysosomal-associated membrane protein 1 (LAMP-1)). Although both CD56dim and CD56bright NK cell populations can express IFN-gamma in response to iRBC, CD25 and LAMP-1 are up-regulated only by CD56dim NK cells and CD69 is up-regulated to a greater extent in this subset; by contrast, perforin and granzyme A are preferentially up-regulated by CD56bright NK cells. NK cells expressing IFN-gamma in response to iRBC always coexpress CD69 and CD25 but rarely LAMP-1, suggesting that individual NK cells respond to iRBC either by IFN-gamma production or cytotoxicity. Furthermore, physical contact with iRBC can, in a proportion of donors, lead to NK cell cytoskeletal reorganization suggestive of functional interactions between the cells. These observations imply that individuals may vary in their ability to mount an innate immune response to malaria infection with obvious implications for disease resistance or susceptibility.     

Differential upregulation of chemokine receptors on CD56+ NK cells and their transmigration to the site of infection in tuberculous pleurisy

Chemokines and their receptors orchestrate leukocyte recruitment and confer immunity during Mycobacterium tuberculosis infection. The immunoregulatory and cytotoxic activities of natural killer (NK) cells are essential at the site of infection during tuberculous pleurisy. The frequency, subtypes, and expression of phenotype markers and chemokine receptors on NK cells were assessed by flow cytometry in tuberculous (TB) and nontuberculous (NTB) pleural fluid (PF). Chemotaxis was also shown in response to chemokines. A significant decrease in CD56^dim with no change in CD56^bright NK cells was observed, while a significant increase in activation markers and Toll-like receptors (TLRs) was observed on TB-PF CD56^bright NK cells. Significantly increased expression of chemokine receptors CCR1, CCR2 and CCR7 on CD56^bright and CCR5 on CD56^dim NK cells was observed in the TB group. Transmigration of TB-PF NK cells was significantly high in response to IL-8, IP-10, MCP-1 and SLC. Transmigrated TB-NK cells showed a significant increase in CXCR2, CCR2 and CCR7 expression. The study suggests that CD56^bright NK cells may recognize M. tuberculosis directly using TLRs, HLA-DR and express CD69 as an early activation marker. In addition, CC chemokines induce activation signals in chemokine receptors mediating differential NK cell migration to the site. Thus, NK cells act as first direct sensors and effectors in mycobacterial infection.