Chemokines activate natural killer cells through heterotrimeric G-proteins: implications for the treatment of AIDS and cancer

CXCL10 Chemokine: A Critical Player in RNA and DNA Viral Infections

Chemokines constitute a group of small, secreted proteins that regulate leukocyte migration and contribute to their activation. Chemokines are crucial inflammatory mediators that play a key role in managing viral infections, during which the profile of chemokine expression helps shape the immune response and regulate viral clearance, improving clinical outcome. In particular, the chemokine ligand CXCL10 and its receptor CXCR3 were explored in a plethora of RNA and DNA viral infections. In this review, we highlight the expression profile and role of the CXCL10/CXCR3 axis in the host defense against a variety of RNA and DNA viral infections. We also discuss the interactions among viruses and host cells that trigger CXCL10 expression, as well as the signaling cascades induced in CXCR3 positive cells.

Clinical Characteristics and Immune Status of Patients with Severe Fever with Thrombocytopenia Syndrome

Severe fever with thrombocytopenia syndrome (SFTS) is a novel infectious disease caused by bunya virus. The purpose of this study was to investigate the clinical characteristics of SFTS patients and their virus-related immune disorders in vivo. Patients with SFTS admitted to Nanjing Drum Tower Hospital from 2017 to 2020 were retrospectively analyzed, and divided into survival group and death group according to the 28-day survival. Clinical characteristics and laboratory examination results of SFTS patients were recorded, and dynamic changes of immune function and inflammatory factors were statistically analyzed. Prolonged activated prothrombin time (APTT) (p = 0.001), high viral load (p = 0.001), and elevated human leukocyte antigen DR (HLA-DR) level (p = 0.002) were independent prognostic risk factors for SFTS patients. Compared to the survival group, the nonsurvival group was more prone to hemorrhagic and neurological symptoms (p < 0.05). Natural kill (NK) cell count, interleukin-10, interferon-α, and tumor necrosis factor-α scores in the nonsurvival group continued to increase after admission, while CD3+ T, CD4+ T, and CD8+ T cell counts continued to decrease. CD3+ T lymphocyte count was negatively correlated with viral load (R = 0.3883, p < 0.001), CD4+ T lymphocyte count was negatively correlated with viral load (R = 0.28933, p < 0.001), CD8+ T lymphocyte count was negatively correlated with viral load (R = 0.781, p < 0.001), and HLA-DR was positively correlated with viral load (R = 0.489, p < 0.001). High viral load, prolonged APTT time, and elevated HLA-DR level are independent prognostic risk factors for SFTS patients. The T lymphocyte subsets of SFTS patients continue to decrease after infection, and the number of T lymphocyte subsets can reflect the severity of the disease.

Innate Lymphoid Cells and Natural Killer Cells in Bacterial Infections: Function, Dysregulation, and Therapeutic Targets

Infectious diseases represent one of the largest medical challenges worldwide. Bacterial infections, in particular, remain a pertinent health challenge and burden. Moreover, such infections increase over time due to the continuous use of various antibiotics without medical need, thus leading to several side effects and bacterial resistance. Our innate immune system represents our first line of defense against any foreign pathogens. This system comprises the innate lymphoid cells (ILCs), including natural killer (NK) cells that are critical players in establishing homeostasis and immunity against infections. ILCs are a group of functionally heterogenous but potent innate immune effector cells that constitute tissue-resident sentinels against intracellular and extracellular bacterial infections. Being a nascent subset of innate lymphocytes, their role in bacterial infections is not clearly understood. Furthermore, these pathogens have developed methods to evade the host immune system, and hence permit infection spread and tissue damage. In this review, we highlight the role of the different ILC populations in various bacterial infections and the possible ways of immune evasion. Additionally, potential immunotherapies to manipulate ILC responses will be briefly discussed.

Molecular Examination of Differentially Expressed Genes in the Brains of Experimental Autoimmune Encephalomyelitis Mice Post Herceptin Treatment

Objective

Herceptin (trastuzumab) is an approved drug for treating HER2⁺ breast cancer patients, but its use for other diseases is not established. We sought to investigate the effects of Herceptin on ameliorating experimental autoimmune encephalomyelitis (EAE) and to examine its effects on the expression of various genes.

Methods

We used in-silico analysis of publicly available data, qRT-PCR, and immunohistochemistry (IHC) to determine the expression of HER2⁺ cells in the brains of EAE mice. IHC was also utilized to determine the anti-inflammatory effects of Herceptin. The ability of Herceptin to alleviate the EAE clinical score was measured in these mice. Bioinformatics analysis of publicly available data and qRT-PCR were performed to investigate the differentially expressed genes that were either up-regulated or down-regulated during the high clinical score (HCS) of the disease.

Results

We observed that HER2/Erbb2, the receptor for Herceptin is upregulated in the brains of EAE mice when the brains were examined at the HCS stage. Further, we demonstrated that Herceptin ameliorates the EAE disease, increasing re-myelination, reducing brain inflammation, CD3⁺ T cell accumulation, and HER2⁺ cells in the brains of these mice. Molecular analysis demonstrated the expression of different genes that were either up-regulated or down-regulated during the HCS of the disease. Our combined bioinformatics and qRT-PCR analyses show increased mRNA expression of Atp6v0d2, C3, C3ar1, Ccl3, Ccl6, Cd74, Clec7a, Cybb, H2-Aa, Hspb1, Lilr4b, Lilrb4a, Mpeg1, Ms4a4a, Ms4a6c, Saa3, Serpina3n and Timp1, at HCS. Except for the mRNA levels of Cd74 and Clec7a which were increased at HCS when Herceptin was used in both prophylactic and therapeutic regimens, the levels of other described mRNAs were reduced.

Conclusion

These novel findings show that Herceptin ameliorates the clinical score in EAE mice and are the first to investigate in detail the differential gene expression post-treatment with the drug.

Persons who inject drugs (PWID) retain functional NK cells, dendritic cell stimulation, and adaptive immune recall responses despite prolonged opioid use

Previous literature suggests that acute opioid use results in the functional impairment of the immune response, thereby decreasing resistance to viral infection. Here, we assessed if innate and adaptive immune responses are compromised ex vivo in persons who inject drugs (PWID) and whether long-term injection drug use may impact host susceptibility to in vitro HIV infection. We measured the frequency, activation state, and functional profile of NK cells, dendritic cells, and CD4+ and CD8+ T cells in low-risk PWID who do not share needles, high-risk needle-sharing PWID, and control donors who did not inject drugs. We also assessed plasma levels of inflammatory markers and CD4+ T cell susceptibility to HIV infection. We observed a significant increase in the amount of sCD14 (P = 0.0023, n = 16) and sCD163 (P = 0.0001, n = 16) in the plasma of PWID compared to controls. Evidence of constitutive activation was noted in PWID as compared to controls with increased CD69 expression in CD56dim NK cells (P = 0.0103, n = 26) and increased CD38 and HLA-DR expression in CD4+ T cells (P = 0.0355, n = 23). However, no innate or adaptive functional differences were detected between PWID and controls, including: NK cell direct or antibody-dependent cellular cytotoxicity poly-functional response, TLR-stimulated dendritic cell/NK crosstalk, CD8+ T cell response to Staphylococcal enterotoxin B or CMV/EBV/FLU peptides, or constitutive or anti-CD3/CD28-stimulated CD4+ T cell infectivity with CCR5-tropic or CXCR4-tropic HIV-1 isolates. Our data indicate that PWID who utilize opioids over as prolonged time frame can retain a functional ex vivo immune response without a measurable increase in CD4+ T cell infectivity suggesting that leukocytes from PWID are not intrinsically more susceptibility to infection with HIV than non-PWID controls.

Drugs for Multiple Sclerosis Activate Natural Killer Cells: Do They Protect Against COVID-19 Infection?

COVID-19 infection caused by the newly discovered coronavirus severe acute respiratory distress syndrome virus-19 (SARS-CoV-2) has become a pandemic issue across the globe. There are currently many investigations taking place to look for specific, safe and potent anti-viral agents. Upon transmission and entry into the human body, SARS-CoV-2 triggers multiple immune players to be involved in the fight against the viral infection. Amongst these immune cells are NK cells that possess robust antiviral activity, and which do not require prior sensitization. However, NK cell count and activity were found to be impaired in COVID-19 patients and hence, could become a potential therapeutic target for COVID-19. Several drugs, including glatiramer acetate (GA), vitamin D₃, dimethyl fumarate (DMF), monomethyl fumarate (MMF), natalizumab, ocrelizumab, and IFN-β, among others have been previously described to increase the biological activities of NK cells especially their cytolytic potential as reported by upregulation of CD107a, and the release of perforin and granzymes. In this review, we propose that such drugs could potentially restore NK cell activity allowing individuals to be more protective against COVID-19 infection and its complications.

The Inhibitory G Protein α-Subunit, Gαz, Promotes Type 1 Diabetes-Like Pathophysiology in NOD Mice

The α-subunit of the heterotrimeric Gz protein, Gαz, promotes β-cell death and inhibits β-cell replication when pancreatic islets are challenged by stressors. Thus, we hypothesized that loss of Gαz protein would preserve functional β-cell mass in the nonobese diabetic (NOD) model, protecting from overt diabetes. We saw that protection from diabetes was robust and durable up to 35 weeks of age in Gαz knockout mice. By 17 weeks of age, Gαz-null NOD mice had significantly higher diabetes-free survival than wild-type littermates. Islets from these mice had reduced markers of proinflammatory immune cell infiltration on both the histological and transcript levels and secreted more insulin in response to glucose. Further analyses of pancreas sections revealed significantly fewer terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling (TUNEL)-positive β-cells in Gαz-null islets despite similar immune infiltration in control mice. Islets from Gαz-null mice also exhibited a higher percentage of Ki-67-positive β-cells, a measure of proliferation, even in the presence of immune infiltration. Finally, β-cell-specific Gαz-null mice phenocopy whole-body Gαz-null mice in their protection from developing hyperglycemia after streptozotocin administration, supporting a β-cell-centric role for Gαz in diabetes pathophysiology. We propose that Gαz plays a key role in β-cell signaling that becomes dysfunctional in the type 1 diabetes setting, accelerating the death of β-cells, which promotes further accumulation of immune cells in the pancreatic islets, and inhibiting a restorative proliferative response.

Rat embryonic fibroblasts immortalized by MRPS18-2 protein are target for NK-cells

Overexpression of the human mitochondrial ribosomal protein MRPS18-2 (S18-2) led to immortalization of primary rat embryonic fibroblasts (REFs). The derived cells (18IM) expressed embryonic stem cell markers. Noteworthy, genes encoding the COX family proteins were up-regulated significantly. It is known that the COX family proteins are involved in the regulation of immune response. In the present work we demonstrate that 18IM cells behave like stem cells when subjected to directed differentiation in vitro. However, unlike stem cells, 18IM cells do not develop tumors in vivo, in SCID mice. This phenomenon is observed due to the strong natural killer (NK) cell immunogenicity. 18IM cells were better recognized by NK cells, compared with primary REFs, as was shown by a standard NK killing assay. Our data explain asymmetry in behavior of stem-like cells in vivo and in vitro, and this support the notion that stem and/or cancer-initiating cells are preferred targets for NK-cells. Concluding, the S18-2 protein is a putative target for cancer vaccines.

Glatiramer Acetate, Dimethyl Fumarate, and Monomethyl Fumarate Upregulate the Expression of CCR10 on the Surface of Natural Killer Cells and Enhance Their Chemotaxis and Cytotoxicity

In vitro harnessing of immune cells is the most important advance in the field of cancer immunotherapy. Results shown in the current paper may be used to harness natural killer (NK) cells in vitro. It is observed that drugs used to treat multiple sclerosis such as glatiramer acetate, dimethyl fumarate, and monomethyl fumarate upregulate the expression of chemokines receptor 10 (CCR10) on the surface of human IL-2-activated NK cells. This is corroborated with increased chemotaxis of these cells toward the concentration gradients of the ligands for CCR10, namely CCL27 and CCL28. It is also demonstrated that these three drugs enhance NK cell cytotoxicity against tumor target cells, an activity that is abrogated by prior incubation of the cells with anti-CCR10 antibody. Because CCL27 and CCL28 are secreted by selective tumor types such as malignant melanoma, squamous cell carcinomas, and colorectal cancer, respectively, it is hypothesized that activated NK cells may be harnessed in vitro with any of these drugs before utilizing them as a therapeutic modality for cancer.

The TLR-2/TLR-6 agonist macrophage-activating lipopeptide-2 augments human NK cell cytotoxicity when PGE2 production by monocytes is inhibited by a COX-2 blocker

Macrophage-activating lipopeptide-2 (MALP-2) is a potent inducer of proinflammatory cytokine secretion by macrophages, monocytes, and dendritic cells. MALP-2 was reported to be involved in natural killer (NK) cell activation and ensuing tumor rejection. However, the mechanism of MALP-2-mediated NK cell activation remained unclear. Therefore, we studied the effects of MALP-2 on cultured human NK cells. We found that MALP-2 had no direct effect on NK cells. Instead, MALP-2 acted on monocytes and triggered the release of different molecules such as interleukin (IL)-1β, IL-6, IL-10, IL-12, IL-15, interferon gamma-induced protein (IP-10), and prostaglandin (PG)-E2. Our data show that monocyte-derived IP-10 could significantly induce NK cell cytotoxicity as long as the immunosuppression by PGE2 is specifically inhibited by cyclooxygenase (COX)-2 blockade. In summary, our results show that MALP-2-mediated stimulation of monocytes results in the production of several mediators which, depending on the prevailing conditions, affect the activity of NK cells in various ways. Hence, MALP-2 administration with concurrent blocking of COX-2 can be considered as a promising approach in MALP-2-based adjuvant tumor therapies.

Monomethyl fumarate augments NK cell lysis of tumor cells through degranulation and the upregulation of NKp46 and CD107a

Dimethyl fumarate (DMF) is a new drug used to treat multiple sclerosis (MS) patients. Here, we examined the effects of DMF and the DMF metabolite monomethyl fumarate (MMF) on various activities of natural killer (NK) cells. We demonstrated that MMF augments the primary CD56(+), but not CD56(-), NK cell lysis of K562 and RAJI tumor cells. MMF induced NKp46 expression on the surface of CD56(+), but not CD56(-), NK cells after incubation for 24 h. This effect was closely correlated with the upregulation of CD107a expression on the surface of CD56(+) NK cells and the induction of Granzyme B release from these cells through this metabolite. An anti-NKp46 antibody inhibited the MMF-induced upregulation of CD107a and the lysis of tumor cells through CD56(+) NK cells. Thus, these results are the first to show that MMF augments CD56(+) NK cell lysis of tumor target cells, an effect mediated through NKp46. This novel effect suggests the use of MMF for therapeutic and/or preventive protocols in cancer.

Detection and evaluation of immunofunction of patients with severe fever with thrombocytopenia syndrome

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging infectious disease caused by SFTS virus (SFTSV) with a high fatality rate. But the immunofunction was still unclear. The objective of our study was to assess the immunofunction in SFTS patients. Immunofunction test with flow cytometry which contains CD3+, CD4+ and CD8+ T lymphocytes, B cells and NK cells would be used for detecting serum samples collected from 34 SFTS cases and 20 healthy donors. We found that CD3+ and CD4+ T lymphocytes were significantly diminished in SFTS compared to normal control. In contrast, the percentage of NK cells was elevated. Further analysis revealed that the number of CD3+ and CD4+ T lymphocytes showed that there was a more robust pattern of depression in acute phase and severe SFTS infection compared to the patients in recovery phase and mild SFTS infection. But NK cells were significantly increased in acute phase and severe SFTS. They reverted to the near normal levels in convalescent phase. Additionally, the levels of CD3+ and CD4+ T lymphocytes progressively decreased in death group when compared with the survival group, but the level of B cells was higher. The damages of immune system were obvious, and the immune dysfunction might be partly responsible for disease progression of patients with SFTSV infection.

A one year follow-up study of natural killer and dendritic cells activities in multiple sclerosis patients receiving glatiramer acetate (GA)

Background

Multiple sclerosis (MS) is a chronic inflammatory, demyelinating and neurodegenerative disease. It is thought to be mediated by CD4⁺ Th1/Th17 cells. More recently, cells of the innate immune system such as dendritic cells (DCs) and natural killer (NK) cells have been in focus. Glatiramer acetate (GA) is an approved drug for treating MS patients.

Methodology/Principal Findings

In the current study we examined the activities of NK and DCs in nine relapsing remitting MS patients for up to one year after initiation of GA treatment. We observed that NK cells isolated from most of these patients have increased cytotoxic activity against K562 cells. Further analysis showed that the same NK cells lysed both autologous immature (i) and mature (m) DCs. In most patients this increased activity was correlated with increased NK cell activating cytotoxicity receptors such as NKp30, NKp44, NKp46 and NKG2D, and reduced expression of the inhibitory molecule CD158 on the surface of these NK cells. The expression of HLA-DR was increased on iDCs and mDCs in the majority of the patients, but no consistency was observed for the expression of HLA-I or HLA-E. Also, the co-stimulatory receptors CD80, CD83 or CD86 expression was down-regulated on iDCs and mDCs in most cases. Further, the expression of CCR6 was increased on mDCs at later time points of therapy (between 32–48 weeks).

Conclusions/Significance

Our results are the first showing the effects of GA treatment on NK cells in MS patients, which may impact future use of this and other drugs to treat this disease.

On the role of natural killer cells in neurodegenerative diseases

Natural killer (NK) cells exert important immunoregulatory functions by releasing several inflammatory molecules, such as IFN-γ and members of chemokines, which include CCL3/MIP-1α and CCL4/MIP-1β. These cells also express heptahelical receptors, which are coupled to heterotrimeric G proteins that guide them into inflamed and injured tissues. NK cells have been shown to recognize and destroy transformed cells and virally-infected cells, but their roles in neurodegenerative diseases have not been examined in detail. In this review, I will summarize the effects of NK cells in two neurodegenerative diseases, namely multiple sclerosis and globoid cell leukodystrophy. It is hoped that the knowledge obtained from these diseases may facilitate building rational protocols for treating these and other neurodegenerative or autoimmune diseases using NK cells and drugs that activate them as therapeutic tools.

Effects of lysophospholipids on tumor microenvironment

The effects of lysophospholipids (LPLs) on cancer microenvironment is a vast and growing field. These lipids are secreted physiologically by various cell types. They play highly important roles in the development, activation and regulation of the immune system. They are also secreted by cancerous cells and there is a strong association between LPLs and cancer. It is clear that these lipids and in particular sphingosine 1-phosphate (S1P) and lysophosphatidic acid (LPA) play major roles in regulating the growth of tumor cells, and in manipulating the immune system. These activities can be divided into two parts; the first involves the ability of S1P and LPA to either directly or through some of the enzymes that generate them such as sphingosine kinases or phospholipases, induce the motility and invasiveness of tumor cells. The second mechanism involves the recently discovered effects of these lipids on the anti-tumor effector natural killer (NK) cells. Whereas S1P and LPA induce the recruitment of these effector cells, they also inhibit their cytolysis of tumor cells. This may support the environment of cancer and the ability of cancer cells to grow, spread and metastasize. Consequently, LPLs or their receptors may be attractive targets for developing drugs in the treatment of cancer where LPLs or their receptors are up-regulated.

Natural killer cells that respond to human immunodeficiency virus type 1 (HIV‐1) peptides are associated with control of HIV‐1 infection

Human immunodeficiency virus (HIV)-specific natural killer (CD3- cells), CD4, and CD8 T cellular responses were determined in 79 HIV‐1-infected women in response to HIV‐1 peptide pools (Gag, Pol, Nef, Reg, and Env) with use of a whole‐blood intracellular cytokine staining assay that measures interferon-γ and/or interleukin-2. HIV‐specific CD3- cell responses to any region (Env and Reg predominantly targeted) were associated with lower viral load (P = .031) and higher CD4 T cell count (P = .015). Env‐specific CD3- cell responses were stronger in women who had both Gag CD4 and CD8 T cell responses and, in turn, was associated with lower viral load (P = .005). CD3- cell responders had significantly higher representation of CD4 T cell responses to Env and Reg (P = .012 and P = .015, respectively) and higher magnitudes of CD4 T cell responses (P = .017 and P = .037, respectively) than did nonresponders. Peptide‐specific natural killer cells are associated with markers of less severe disease progression among HIV‐1-infected women (lower viral load and higher CD4 T cell count) and with stronger HIV‐specific T cell responses.

Role of chemokines in the biology of natural killer cells

Natural killer (NK) cells represent a major subpopulation of lymphocytes. These cells have effector functions as they recognize and kill transformed cells as well as microbially infected cells. In addition, alloreactive NK cells have been successfully used to treat patients with acute myeloid leukemia and other hematological malignancies. NK cells are also endowed with immunoregulatory functions since they secrete cytokines such as IFN-γ, which favor the development of T helper 1 (Th1) cells, and chemokines such as CCL3/MIP-1α and CCL4/MIP-1β, which recruit various inflammatory cells into sites of inflammation. In human blood, NK cells are divided into CD56(bright) CD16(dim) and CD56(dim) CD16(bright) subsets. These subsets have different phenotypic expression and may have different functions; the former subset is more immunoregulatory and the latter is more cytolytic. The CD56(bright)CD16(dim) NK cells home into tissues such as the peripheral lymph nodes (LNs) under physiological conditions because they express the LN homing receptor CCR7 and they respond to CCL19/MIP-3β and CCL21/SLC chemokines. They also distribute into adenoid tissues or decidual uterus following the CXCR3/CXCL10 or CXCR4/CXCL12 axis. On the other hand, both NK cell subsets migrate into inflammatory sites, with more CD56(dim)CD16(bright) NK cells distributing into inflamed liver and lungs. CCR5/CCL5 axis plays an important role in the accumulation of NK cells in virally infected sites as well as during parasitic infections. CD56(bright)CD16(dim) cells also migrate into autoimmune sites such as inflamed synovial fluids in patients having rheumatoid arthritis facilitated by the CCR5/CCL3/CCL4/CCL5 axis, whereas they distribute into inflamed brains aided by the CX₃CR1/CX₃CL1 axis. On the other hand, CD56(dim)CD16(bright) NK cells accumulate in the liver of patients with primary biliary disease aided by the CXCR1/CXCL8 axis. However, the types of chemokines that contribute to their accumulation in target organs during graft vs. host (GvH) disease are not known. Further, chemokines activate NK cells to become highly cytolytic cells known as CC chemokine-activated killer (CHAK) cells that kill tumor cells. In summary, chemokines whether secreted in an autocrine or paracrine fashion regulate various biological functions of NK cells. Depending on the tissue and the chemokine secreted, NK cells may ameliorate the disease such as their roles in combating tumors or virally infected cells, and their therapeutic potentials in treating leukemias and other hematological malignancies, as well as reducing the incidence of GvH disease. In contrast, they may exacerbate the disease by damaging the affected tissues through direct cytotoxicity or by the release of multiple inflammatory cytokines and chemokines. Examples are their deleterious roles in autoimmune diseases such as rheumatoid arthritis and primary biliary cirrhosis.

Splenic natural killer cell activity in two models of experimental neurodegenerative diseases

Natural killer (NK) cells are antitumour/anti-viral effectors and play important roles in shaping the immune system, but their role in neurodegenerative diseases is not clear. Here, we investigated the fate of these cells in two neurodegenerative diseases. In the first model, the activity of NK cells was examined in mice with experimental autoimmune encephalomyelitis (EAE) treated with glatiramer acetate (GA or Copaxone), a drug used to treat EAE in animals and multiple sclerosis in human. The second disease model is twitcher (Galc(twi)/Galc(twi)) mice, which represents an authentic model of human Krabbe's disease. Administration of GA ameliorated EAE in SJL mice corroborated with isolating NK cells that expressed higher killing than cells isolated from vehicle-dosed animals against immature or mature dendritic cells (DCs). However, this drug showed no effect on the numbers of NK cells or the expression of CD69 molecule. On the other hand, NK cells either disappeared from the spleens or were present in low numbers in the white pulp areas of Galc(twi)/Galc(twi) mice, which have increased D-galactosyl-beta1-1'-sphingosine (GalSph) levels. Analysis by confocal microscopy shows that NK cells found in the spleens of Galc(twi)/Galc(twi) mice were apoptotic. Incubating NK cells in vitro with GalSph induced the apoptosis in these cells, confirming the results of twitcher mice. Our results provide the first evidence showing that amelioration of EAE in mice is corroborated with NK cell lysis of antigen-presenting DCs, whereas NK cell distribution into the spleen is altered in a devastating lipid disorder corroborated with induction of their apoptosis.

Splenic natural killer cell activity in two models of experimental neurodegenerative diseases

Natural killer (NK) cells are antitumour/anti-viral effectors and play important roles in shaping the immune system, but their role in neurodegenerative diseases is not clear. Here, we investigated the fate of these cells in two neurodegenerative diseases. In the first model, the activity of NK cells was examined in mice with experimental autoimmune encephalomyelitis (EAE) treated with glatiramer acetate (GA or Copaxone), a drug used to treat EAE in animals and multiple sclerosis in human. The second disease model is twitcher (Galc(twi)/Galc(twi)) mice, which represents an authentic model of human Krabbe's disease. Administration of GA ameliorated EAE in SJL mice corroborated with isolating NK cells that expressed higher killing than cells isolated from vehicle-dosed animals against immature or mature dendritic cells (DCs). However, this drug showed no effect on the numbers of NK cells or the expression of CD69 molecule. On the other hand, NK cells either disappeared from the spleens or were present in low numbers in the white pulp areas of Galc(twi)/Galc(twi) mice, which have increased D-galactosyl-beta1-1'-sphingosine (GalSph) levels. Analysis by confocal microscopy shows that NK cells found in the spleens of Galc(twi)/Galc(twi) mice were apoptotic. Incubating NK cells in vitro with GalSph induced the apoptosis in these cells, confirming the results of twitcher mice. Our results provide the first evidence showing that amelioration of EAE in mice is corroborated with NK cell lysis of antigen-presenting DCs, whereas NK cell distribution into the spleen is altered in a devastating lipid disorder corroborated with induction of their apoptosis.

Induction of the Galpha(q) signaling cascade by the human immunodeficiency virus envelope is required for virus entry

Binding of human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein (Env) with the primary receptor CD4 and one of two coreceptors, CXCR4 or CCR5, activates a signaling cascade resulting in Rac-1 GTPase activation and stimulation of actin cytoskeletal reorganizations critical for HIV-1-mediated membrane fusion. The mechanism by which HIV-1 Env induces Rac-1 activation and subsequent actin cytoskeleton rearrangement is unknown. In this study, we show that Env-mediated Rac-1 activation is dependent on the activation of Galpha(q) and its downstream targets. Fusion and Rac-1 activation are mediated by Galpha(q) and phospholipase C (PLC), as shown by attenuation of fusion and Rac-1 activation in cells either expressing small interfering RNA (siRNA) targeting Galpha(q) or treated with the PLC inhibitor U73122. Rac-1 activation and fusion were also blocked by multiple protein kinase C inhibitors, by inhibitors of intracellular Ca2+ release, by Pyk2-targeted siRNA, and by the Ras inhibitor S-trans,trans-farnesylthiosalicylic acid (FTS). Fusion was blocked without altering cell viability or cell surface localization of CD4 and CCR5. Similar results were obtained when cell fusion was induced by Env expressed on viral and cellular membranes and when cell lines or primary cells were the target. Treatment with inhibitors and siRNA specific for Galpha(i) or Galpha(s) signaling mediators had no effect on Env-mediated Rac-1 activation or cell fusion, indicating that the Galpha(q) pathway alone is responsible. These results could provide a new focus for therapeutic intervention with drugs targeting host signaling mediators rather than viral molecules, a strategy which is less likely to result in resistance.

Microenvironmental regulation of biomacromolecular therapies

There is currently great interest in molecular therapies to treat various diseases, and this has prompted extensive efforts to achieve target-specific and controlled delivery of bioactive macromolecules (for example, proteins, antibodies, DNA and small interfering RNA) through the design of smart drug carriers. By contrast, the influence of the microenvironment in which the target cell resides and the effect it might have on the success of biomacromolecular therapies has been under-appreciated. The extracellular matrix (ECM) component of the cellular niche may be particularly important, as many diseases and injury disrupt the normal ECM architecture, the cell adhesion to ECM, and the subsequent cellular activities. This Review will discuss the importance of the ECM and the ECM-cell interactions on the cell response to bioactive macromolecules, and suggest how this information could lead to new criteria for the design of novel drug delivery systems.

The chemokine CXCL14 (BRAK) stimulates activated NK cell migration: implications for the downregulation of CXCL14 in malignancy

OBJECTIVE

The primary function of chemokines is the regulation of leukocyte trafficking by stimulating directional chemotaxis. The chemokine CXCL14 (BRAK) is highly expressed in all normal tissues, but is not expressed in most malignant tissues. The chemotactic activity of CXCL14 has been difficult to characterize. Recently it was reported that CXCL14 is a chemoattractant for activated monocytes and immature dendritic cells. Given that CXCL14 is downregulated upon transition to malignancy, we sought to characterize whether CXCL14 might play a role in NK cell chemotaxis.

METHODS

Human natural killer (NK) cells were isolated from buffy coats obtained from normal volunteers and were activated with lymphocyte conditioned media, IL-2, and ionomycin. Standard transwell chemotaxis assays, proliferation assays, and chromium release cell cytotoxicity assays were performed.

RESULTS

CXCL14 was found to stimulate migration of activated human NK cells in transwell chemotaxis assays by 1.4-fold. Similarly, it increased migration of an IL-2-dependent natural killer leukemia (NKL) cell line by 1.9-fold. Antisera against CXCL14 or pertussis toxin blocked this chemotactic effect. However, CXCL14 did not affect the proliferation or cytotoxic activity of normal human NK cells. CXCL14 also stimulated the chemotaxis of immature monocyte-derived dendritic cells.

CONCLUSIONS

CXCL14 may play a role in the trafficking of NK cells to sites of inflammation or malignancy. In addition, the downregulation of the expression of CXCL14 might be an important step in successful oncogenesis to prevent NK immune surveillance of the malignancy.

Insights into seven and single transmembrane-spanning domain receptors and their signaling pathways in human natural killer cells

Human natural killer (NK) cells are important cells of the innate immune system. These cells perform two prominent functions: the first is recognizing and destroying virally infected cells and transformed cells; the second is secreting various cytokines that shape up the innate and adaptive immune re-sponses. For these cells to perform these activities, they express different sets of receptors. The receptors used by NK cells to extravasate into sites of injury belong to the seven transmembrane (7TM) family of receptors, which characteristically bind heterotrimeric G proteins. These receptors allow NK cells to sense the chemotactic gradients and activate second messengers, which aid NK cells in polarizing and migrating toward the sites of injured tissues. In addition, these receptors determine how and why human resting NK cells are mainly found in the bloodstream, whereas activated NK cells extravasate into inflammatory sites. Receptors for chemokines and lysophospholipids belong to the 7TM family. On the other hand, NK cells recognize invading or transformed cells through another set of receptors that belong to the single transmembrane-spanning domain family. These receptors are either inhibitory or activating. Inhibitory receptors contain the immune receptor tyrosine-based inhibitory motif, and activating receptors belong to either those that associate with adaptor molecules containing the immune receptor tyrosine-based activating motif (ITAM) or those that associate with adaptor molecules containing motifs other than ITAM. This article will describe the nature of these receptors and examine the intracellular signaling pathways induced in NK cells after ligating both types of receptors. These pathways are crucial for NK cell biology, development, and functions.

Compartmentalization of human natural killer cells

Human natural killer (NK) cells are bone marrow-derived cells that are found in the bloodstream, but can extravasate into various tissue sites upon inflammation. NK cells that migrate toward inflamed sites must be activated prior to their extravasation. However, the factors responsible for NK cell compartmentalization are not clearly defined. Resting human NK cells (CD16(-) and CD16(+)) express constitutive chemokine receptors, as well as receptors that have both constitutive and inflammatory functions. Upon activation, NK cells up-regulate the expression of the inflammatory chemokine receptors which facilitate their distribution into inflammatory sites. However, chemokines are not expected to play any role in maintaining resting NK cells in the blood circulation. In contrast, members of the lysolipids which are abundant in the bloodstream may be the major factors responsible for maintaining resting NK cells in the bloodstream, and also for facilitating their extravasation into inflamed tissues. Both resting and activated NK cells express receptors for various lysolipids. Hence, chemoattractants which include chemokines and lysolipids have important roles in determining the compartmentalization of NK cells where resting NK cells are found in the blood circulation, and activated NK cells extravasate into inflamed sites.

Role of cytokines and chemokines in the regulation of innate immunity and HIV infection

The earliest defense against microbial infection is represented by the responses of the innate (or natural) immune system, that also profoundly regulates the adaptive (or acquired) T- and B-cell immune responses. Activation of the innate immune system is primed by microbial invasion in response to conserved structures present in large groups of microorganisms (LPS, peptidoglycan, double-stranded RNA), and is finely tuned by different cell types (including dendritic cells, macrophages, natural killer cells, natural killer T cells, and gammadelta T cells). In addition, several soluble factors (complement components, defensins, mannose-binding lectins, interferons, cytokines and chemokines) can play a major role in the regulation of both the innate and adaptive immunity. In this review, we will briefly overview the regulation of some cellular subsets of the innate immune system particularly involved in human immunodeficiency virus (HIV) infection and then focus our attention on those cytokines and chemokines whose levels of expression are more profoundly affected by HIV infection and that, conversely, can modulate virus infection and replication.

d-Galactosyl-β1-1′-sphingosine and d-glucosyl-β1-1′-sphingosine induce human natural killer cell apoptosis

Natural killer (NK) cells perform multiple biological functions including tumor cell lysis and eradicating virally infected cells. Here, we report for the first time that D-galactosyl-beta1-1' sphingosine and D-glucosyl-beta1- 1' sphingosine damage human NK cells. We show that these cells express T-cell-associated gene-8, the receptor for glycosphingolipids. D-galactosyl-beta1-1' sphingosine and D-glucosyl-beta1-1' sphingosine induce the in vitro chemotaxis of human NK cells. Both D-galactosyl-beta1-1' sphingosine and D-glucosyl-beta1-1' sphingosine inhibit the cytotoxicity and IFN-gamma secretion by these cells. Further analysis shows that the glycosphingolipids D-galactosyl-beta1-1' sphingosine and D-glucosyl-beta1-1' sphingosine but not any other lipid examined, which include D-lactosyl-beta1-1' sphingosine, sphingosine 1-phosphate, sphingosine, lysophosphatidic acid, and phosphatidic acid, induce the apoptosis, globoid-like formation, and multinucleation in human NK cells. These results may have important implications on diseases where glycosphingolipids accumulate.

The discovery of structurally novel CCR1 antagonists derived from a hydroxyethylene peptide isostere template

The present manuscript details the discovery and early fundamental structure-activity relationship studies involving compound 3, a novel hydroxyethylene peptide isostere derived molecule that provides micromolar inhibition of CCL3 binding to its receptor CCR1. Initial studies established this screening hit as a legitimate lead for further medicinal chemistry optimization.

G protein-coupled receptors in natural killer cells

Natural killer (NK) cells are capable of killing tumor as well as virally infected cells. How these cells migrate toward the infected sites in the body is not completely understood. Chemokine receptors that belong to the heptahelical family of receptors and characteristically bind heterotrimeric G proteins are present in most NK cells. Recent results showed that resting NK cells highly express constitutive chemokine receptors (CCR4, CCR7, CXCR4, and CX(3)CR1) with low expression of a limited repertoire of inflammatory chemokine receptors (CCR1 and CXCR3). However, only a subset of these cells expressing the CD56(dim) and adhesion molecule(high) phenotype is capable of in vivo binding to vascular endothelium. Under pathological conditions where inflammatory cytokines are present, these cells are induced to express inflammatory chemokine receptors. Resting as well as activated NK cells also express receptors for another member of the heptahelical family of receptors that bind phosphorylated or glycosylated lysolipids. These include sphingosine 1-phosphate (S1P)(1), S1P(4), and S1P(5), the receptors for S1P; lysophosphatidic acid (LPA)(1), LPA(2), and LPA(3), the receptors for LPA; and T cell death-associated gene 8, the receptor for psychosine. Similar to chemokines, S1P, LPA, and psychosine induce the chemotaxis of NK cells through heterotrimeric G proteins. However, in contrast to chemokines, which enhance the cytotoxicity of NK cells, lysolipids inhibit this function. We hope that gaining knowledge regarding the distribution of activated NK cells toward the sites of tumor growth or virally infected sites will give an advantage in designing strategies using these cells as tools for the prevention and treatment of immunodeficiencies.

Innate immune responses in viral encephalitis

The innate immune system is multifaceted, comprised of preformed factors, cells, and many proteins and lipid mediators produced by those cells. In the CNS these are critical in initiation and amplification of the inflammatory response and in the subsequent elicitation of the specific T cell response to viral encephalitis. Cells that are resident in brain parenchyma and peripheral cells that are recruited both play key roles in the hosts's responses. Unlike the peripheral compartments, in the CNS, non-cytolytic means of eliminating viral infections have been critical, since, in contrast to columnar epithelial cells, neurons are non-renewing. When the innate immune responses are inefficient or absent in viral encephalitis, pathology is more likely. Much more work remains to elucidate all of the critical cells and their mediators, as well as to develop new therapies for infections of the CNS.

Chemokines in cancer

Chemokines participate, by regulating cell trafficking and controlling angiogenesis, in the host response during infection and inflammation. Most of these mechanisms are also operating in cancer. The stimulation of angiogenesis and tumor growth--directly or indirectly through the recruitment of tumor-associated macrophages--are typical situations where chemokines promote tumor development. On the other hand, chemokines could be used to the benefit of cancer patients as they act in the recruitment of dendritic cells (DC) or/and effector cells or for their angiostatic properties. However, chemokine-mediated recruitment of immature DC within tumors, due to factors produced by the tumor milieu, could lead to the induction of immune tolerance and, therefore, novel strategies to eradicate tumors based on chemokines should attempt to avoid this risk.

Uterine chemokines in reproductive physiology and pathology

PROBLEM

Chemokines are increasingly recognized as important regulators of uterine function.

METHODS OF STUDY

The following is a review of uterine chemokines, especially monocyte chemotactic protein (MCP)-1, interleukin (IL)-8, and regulated-upon-activation normal-T-cell-expressed and -secreted (RANTES) protein, in reproductive physiology and pathology.

RESULTS

It is increasingly clear that IL-8, MCP-1, RANTES and their receptors are produced by endometrial, myometrial, and trophoblast cell types in a timed and co-ordinated manner. In addition to the regulation of leukocyte migration and function, uterine chemokines also display specific roles in endometrial angiogenesis, apoptosis, proliferation, and differentiation. IL-8, MCP-1 and RANTES are regulated by local growth factors and cytokines such as tumor necrosis factor-alpha (TNF-alpha), interferon-gamma, and IL-1. IL-8 takes part in cervical ripening and parturition. IL-8, MCP-1 and RANTES are also found at high levels in the peritoneal fluid of women with endometriosis.

CONCLUSION

Co-ordination of chemokine-chemokine receptor interactions plays an important role in the menstrual cycle and successful pregnancy. Moreover, unbalanced chemokine expression contributes to pathologic conditions typified by uncontrolled cellular proliferation, migration and invasion.

Relative preservation of natural killer cell cytotoxicity and number in healthy AIDS patients with low CD4 cell counts

OBJECTIVE

This study examines whether there may be an immune component that protects a relatively rare group of HIV-infected people with very low CD4 cell counts (< or = 50 x 10(6)/l) who have prolonged asymptomatic periods.

DESIGN/METHODS

Three groups were recruited in Miami: (i) healthy low CD4 cell count patients (HLC; n = 30) who, for 9 months had < 50 x 10(6) CD4 cells/l, were asymptomatic and were not on protease inhibitors during that time; (ii) HIV comparison group (Comp; n = 60) who had CD4 cell counts predominantly 150 x 10(6) to 400 x 10(6)/l and never had AIDS Category C symptoms; this group was also followed for CD4 cell count and viral load change over 6 months; and (iii) healthy community controls (n = 33). The study was replicated at the University of California at Los Angeles (UCLA) with HLC (n = 31) versus HIV-negative laboratory controls (n = 28).

RESULTS

The HLC patients were significantly higher than the Comp group on natural killer cell cytotoxicity (NKCC) and natural killer cell number (NK#) despite their lower CD4 cell numbers and higher viral loads. In fact, there was no difference between the HLC group and the healthy community control group in NK# or NKCC. The NK findings were replicated at UCLA. A retrospective analysis showing that higher NKCC was related to fewer prior symptoms in the HLC group, and prospective analysis in the Comp group showing that NK# predicted a lower increase in viral load over 6 months further supported the importance of NK# and NKCC.

CONCLUSIONS

Non-specific cellular immunity may be a factor protecting the health of HIV sero-positive individuals with very low CD4 cell counts.

Analysis of in situ NK cell responses during viral infection

NK cells are required for early control of murine CMV (MCMV) infection, but the distribution of murine NK cells in situ has not been clearly defined. We tested the reactivity of all available NK cell receptor-specific mAbs by immunohistochemistry. Only one mAb, 4D11 (anti-Ly-49G2), was reactive with C57BL/6 tissue sections. mAb 4D11-reactive cells expressed the nuclear morphology and flow cytometric profile of NK cells. In lymphoid organs, NK cells were distributed primarily in the splenic red pulp, between adjacent lobes in lymph node and randomly in the cortex and medulla of the thymus. No NK cells were detected in normal liver sections. Two days following MCMV infection, most splenic NK cells were associated with the lymphoid follicles and marginal zone. By day 3 following infection, the number of liver NK cells had increased significantly and the cells were detected within inflammatory foci. These changes were independent of IL-12, IFN-gamma, and TNF-alpha, as assessed in mice with targeted mutations. Concurrent immunostaining for NK cells and viral Ags revealed close association of NK cells and MCMV-infected cells in the spleen and liver. Similar results were obtained in CD1(-/-) and recombination activation gene-1(-/-) mice lacking NK T or T and B cells, respectively, indicating specificity of staining for NK cells. Thus, following MCMV infection, NK cells accumulate at sites of viral replication in an IL-12-, IFN-gamma-, and TNF-alpha-independent manner.

Human immunodeficiency virus type-1 and chemokines: beyond competition for common cellular receptors

The chemokines and their receptors have been receiving exceptional attention in recent years following the discoveries that some chemokines could specifically block human immunodeficiency virus type 1 (HIV-1) infection and that certain chemokine receptors were the long-sought coreceptors which, along with CD4, are required for the productive entry of HIV-1 and HIV-2 isolates. Several chemokine receptors or orphan chemokine receptor-like molecules can support the entry of various viral strains, but the clinical significance of the CXCR4 and CCR5 coreceptors appear to overshadow a critical role for any of the other coreceptors and all HIV-1 and HIV-2 strains best employ one or both of these coreceptors. Binding of the HIV-1 envelope glycoprotein gp120 subunit to CD4 and/or an appropriate chemokine receptor triggers conformational changes in the envelope glycoprotein oligomer that allow it to facilitate the fusion of the viral and host cell membranes. During these interactions, gp120 appears to be capable of inducing a variety of signaling events, all of which are still not defined in detail. In addition, the more recently observed dichotomous effects, of both inhibition and enhancement, that chemokines and their receptor signaling events elicit on the HIV-1 entry and replication processes has once again highlighted the intricate and complex balance of factors that govern the pathogenic process. Here, we will review and discuss these new observations summarizing the potential significance these processes may have in HIV-1 infection. Understanding the complexities and significance of the signaling processes that the chemokines and viral products induce may substantially enhance our understanding of HIV-1 pathogenesis, and perhaps facilitate the discovery of new ways for the prevention and treatment of HIV-1 disease.

Expression and regulation of chemokine receptors in human natural killer cells

Using flow cytometric and RNase protection assays, this study examined the expression of chemokine receptors in nonactivated natural killer (NK) cells and compared this expression with NK cells activated with interleukin (IL)-2, which either adhered to plastic flasks (AD) or did not adhere (NA). None of the NK cell subsets expressed CXCR2, CXCR5, or CCR5. The major differences between these cells include increased expression of CXCR1, CCR1, CCR2, CCR4, CCR8, and CX(3)CR1 in AD when compared to NA or nonactivated NK cells. The chemotactic response to the CXC and CC chemokines correlated with the receptor expression except that all 3 populations responded to GRO-alpha, despite their lack of CXCR2 expression. Pretreatment of these cells with anti-CXCR2 did not inhibit the chemotactic response to GRO-alpha. In addition, nonactivated and NA cells responded to fractalkine, although they lack the expression of CX(3)CR1. This activity was not inhibited by anti-CX(3)CR1. Viral macrophage inflammatory protein (vMIP)-I, I-309, and TARC competed with the binding of (125)I-309 to AD cells with varying affinities. Transforming growth factor (TGF)-beta1 but not any other cytokine or chemokine examined including interferon (IFN)-gamma, MIP-3beta, macrophage-derived chemokine (MDC), thymus and activation-regulated chemokine (TARC) or I-309, up-regulated the expression of CXCR3 and CXCR4 on NK cell surface. This is correlated with increased chemotaxis of NK cells treated with TGF-beta1 toward stromal cell-derived factor (SDF)-1alpha and interferon-inducible protein-10 (IP-10). Messenger RNA for lymphotactin, RANTES, MIP-1alpha, and MIP-1beta, but not IP-10, monocyte chemotactic protein (MCP)-1, IL-8, or I-309 was expressed in all 3 NK cell subsets. Our results may have implications for the dissemination of NK cells at the sites of tumor growth or viral replication. (Blood. 2001;97:367-375)

A study on the density and distribution of uterine Natural Killer cells at mid pregnancy in mice genetically-ablated for CCR2, CCR 5 and the CCR5 receptor ligand, MIP-1 alpha

Several chemoattractants mediate Natural Killer (NK) cell migration. The CC-chemokines, monocyte inflammatory protein (MIP)-1 alpha, regulated upon activation, normal T cell expressed and secreted (RANTES) and macrophage chemotactic protein (MCP)-1 are the most potent. Peripheral NK cells express the CC-chemokine receptor CCR2, for MCP-1 and CCR5, for MIP-1 alpha and RANTES. These chemokines are detected in the uterus during the estrous cycle and become elevated during pregnancy. To assess the roles of CCR2, CCR5 and MIP-1 alpha in NK cell migration to the uterus and localization within implantation sites, histological analysis was conducted on implantation sites from mice genetically-ablated for CCR2, CCR5, MIP-1 alpha or CCR2 and MIP-1 alpha. Uterine NK (uNK) cell densities in both the decidua basalis and mesometrial lymphoid aggregate of pregnancy (MLAp) of all mutant strains matched wildtype controls. Ratios of vascular: non-vascular uNK cell position were identical in mutants and controls. In the decidua basalis, 25-35% and in the MLAp, 15-20% of uNK cells were perivascular. Intravascular uNK cells were observed in the decidua basalis but not in the MLAp and were more numerous at gestation day 10 than 12. Two measures of uNK cell activation, cell diameter and cytoplasmic granule number, were similar in the mutants and controls. Thus, migration, distribution and activation of NK cells within the pregnant uterus are independent of CCR2, CCR5 and MIP-1 alpha.

The effects of depression, stressful life events, social support, and coping on the progression of HIV infection

This article reviews recent findings concerning the role of psychosocial factors on the progression of HIV. Specifically, we examine the role of depression, stressful life events, social support, and coping on changes in CD4 T-lymphocytes and other indicators of HIV disease progression. Studies have yielded important evidence that depression, stressful life events, low social support, and denial coping may have a detrimental impact on HIV disease course. Delineating the role of psychosocial factors on HIV disease progression may aid in the development of new interventions for this devastating disease.

Intracellular signaling events at the leading edge of migrating cells

Cell migration is an important facet of the life cycle of immune and other cell types. A complex set of events must take place at the leading edge of motile cells before these cells can migrate. Chemokines induce the motility of various cell types by activating multiple intracellular signaling pathways. These include the activation of chemokine receptors, which are coupled to the heterotrimeric G proteins. The release of G beta gamma subunits from chemokine receptors results in the recruitment to the plasma membrane, with subsequent activation of various down-stream signaling molecules. Among these molecules are the pleckstrin homology domain-containing proteins and the phosphoinositide 3-kinase gamma which phosphorylates phospholipids and activates members of the GTP exchange factors (GEFs). These GEFs facilitate the exchange of GTP for GDP in members of GTPases. The latter are important for reorganizing the cell cytoskeleton, and in inducing chemotaxis. Chemokines also induce the mobilization of intracellular calcium from intracellular stores. Second messengers such as inositol 1,4,5 trisphosphate, and cyclic adenosine diphosphate ribose are among those induced by chemokines. In addition, the G beta gamma subunits recruit members of the G protein-coupled receptor kinases, which phosphorylate chemokine receptors, resulting in desensitization and termination of the motility signals. This review will discuss the intracellular signaling pathways induced by chemokines, particularly those activated at the leading edge of migrating cells which lead to cell polarization, cytoskeleton reorganization and motility.

Human NK cells express CC chemokine receptors 4 and 8 and respond to thymus and activation-regulated chemokine, macrophage-derived chemokine, and I-309

NK cells respond to various chemokines, suggesting that they express receptors for these chemokines. In this paper, we show that IL-2-activated NK (IANK) cells express CC chemokine receptor 4 (CCR4) and CCR8, as determined by flow cytometric, immunoblot, and RNase protection assays. Macrophage-derived chemokine (MDC), the ligand for CCR4, induces the phosphorylation of CCR4 within 0.5 min of activating IANK cells with this ligand. This is corroborated with the recruitment of G protein-coupled receptor kinases 2 and 3 and their association with CCR4 in IANK cell membranes. Also, CCR4 is internalized between 5 and 45 min but reappears in the membranes after 60 min of stimulation with MDC. MDC, thymus and activation-regulated chemokine (TARC), and I-309 induce the chemotaxis of IANK cells, an activity that is inhibited upon pretreatment of these cells with pertussis toxin, suggesting that receptors for these chemokines are coupled to pertussis toxin-sensitive G proteins. In the calcium release assay, cross-desensitization experiments showed that TARC completely desensitizes the calcium flux response induced by MDC or I-309, whereas both MDC and I-309 partially desensitize the calcium flux response induced by TARC. These results suggest that TARC utilizes CCR4 and CCR8. Our results are the first to show that IL-2-activated NK cells express CCR4 and CCR8, suggesting that these receptors are not exclusive for Th2 cells.

NK and NK/T cells in human senescence

Natural killer (NK) cells are cytotoxic cells that play a critical role in the innate immune response against infections and tumors. Recent studies on NK cell biology have demonstrated that besides their cytotoxic function, NK cells express cytokine and chemokine receptors and also that they secrete other immunoregulatory cytokines and chemokines, supporting their relevance in the regulation of the immune response by promoting downstream adaptive, Th1 mediated, responses against infections. Immunosenescence is the deterioration of the immune response associated with aging. It is characterized mainly by a defective T cell response, but includes changes in the number and function of other cells of the innate immune system. Age-associated alterations in the number and function of NK cells have been reported. There is a general consensus that a progressive increase in the percentage of NK cells with a mature phenotype occurs in elderly donors associated with an impairment of their cytotoxic capacity when considered on a "per cell" basis. The response of NK cells from elderly individuals to IL-2 or other cytokines is also decreased in terms of proliferation, expression of CD69 and killing of NK-resistant cell lines. Furthermore early IFN-gamma and chemokine production in response to IL-2 or IL-12 is also decreased. However aging does not significantly alter other NK cell functions such as TNF-alpha production or perforin induction in response to IL-2. The percentage of T cells that co-express NK cell markers is also increased in aging. These results indicate that the increase in the number of "classical" mature NK and NK/T cells in aging is associated with a defective functional capacity of NK cells. Low NK cell number or function in elderly individuals is associated with increased mortality risk and increased incidence of severe infections, supporting the role of NK cells in the defense against infections in the elderly.