Natural killer cell memory

Murine NK cell intrinsic cytokine-induced memory-like responses are maintained following homeostatic proliferation

Several recent studies have demonstrated that innate immune NK cells exhibit memory-like properties with enhanced nonspecific and specific recall responses. Cytokine activation alone of murine NK cells induces the differentiation of memory-like cells that are more likely to produce IFN-γ, a key NK cell cytokine important for activation of the immune response. Using an adoptive cotransfer system, we first show that cytokine-induced memory-like responses are NK intrinsic. However, engraftment of donor NK cells in NK-competent hosts is poor because of homeostatic control mechanisms. Therefore, we used alymphoid Rag- and common γ-chain-deficient mice as recipients and observed homeostatic expansion of cotransferred cytokine-activated and control donor NK cells. Despite proliferation of all cells, NK cells derived from those cells originally activated by cytokines retained an intrinsic enhanced capacity to produce IFN-γ when restimulated in vitro with cytokines or target cells. These NK cell memory-like responses persisted for at least 4 wk in alymphoid hosts and 12 wk in NK-competent hosts. These findings indicate that memory-like NK cells can readily self-renew and maintain enhanced function in a lymphopenic host for at least a month.

Liver-resident NK cells confer adaptive immunity in skin-contact inflammation

Liver natural killer (NK) cells were recently reported to possess memory-like properties in contact hypersensitivity (CHS) models. However, the phenotype and origin of these "memory" NK cells cannot be distinguished from other NK cell subpopulations. Here, we define the transcriptional, phenotypic, and functional features of liver NK cell subsets and their roles in mediating CHS. Liver NK cells can be divided into two distinct subsets: CD49a+DX5- and CD49a-DX5+. Substantial transcriptional and phenotypic differences existed between liver CD49a+DX5- NK cells and other NK cell subsets. CD49a+DX5- NK cells possessed memory potential and conferred hapten-specific CHS responses upon hapten challenge. Importantly, CD49a+DX5- NK cells were liver resident and were present in the liver sinusoidal blood, but not the afferent and efferent blood of the liver. Moreover, they appeared to originate from hepatic hematopoietic progenitor/stem cells (HPCs/HSCs) but not from the bone marrow, and maintained their phenotypes in the steady state. Our findings of liver-resident NK cells shed new light on the acquisition of memory-like properties of NK cells.

NK cells and poxvirus infection

In recent years, our understanding of the role of natural killer (NK) cells in the response to viral infection has grown rapidly. Not only do we realize viruses have many immune-evasion strategies to escape NK cell responses, but that stimulation of NK cell subsets during an antiviral response occurs through receptors seemingly geared directly at viral products and that NK cells can provide a memory response to viral pathogens. Tremendous knowledge has been gained in this area through the study of herpes viruses, but appreciation for the significance of NK cells in the response to other types of viral infections is growing. The function of NK cells in defense against poxviruses has emerged over several decades beginning with the early seminal studies showing the role of NK cells and the NK gene complex in susceptibility of mouse strains to ectromelia, a poxvirus pathogen of mice. More recently, greater understanding has emerged of the molecular details of the response. Given that human diseases caused by poxviruses can be as lethal as smallpox or as benign as Molluscum contagiosum, and that vaccinia virus, the prototypic member of the pox family, persists as a mainstay of vaccine design and has potential as an oncolytic virus for tumor therapy, further research in this area remains important. This review focuses on recent advances in understanding the role of NK cells in the immune response to poxviruses, the receptors involved in activation of NK cells during poxvirus infection, and the viral evasion strategies poxviruses employ to avoid the NK response.

NK cell responses to cytomegalovirus infection lead to stable imprints in the human KIR repertoire and involve activating KIRs

Human natural killer (NK) cells are functionally regulated by killer cell immunoglobulin-like receptors (KIRs) and their interactions with HLA class I molecules. As KIR expression in a given NK cell is genetically hard-wired, we hypothesized that KIR repertoire perturbations reflect expansions of unique NK-cell subsets and may be used to trace adaptation of the NK-cell compartment to virus infections. By determining the human "KIR-ome" at a single-cell level in more than 200 donors, we were able to analyze the magnitude of NK cell adaptation to virus infections in healthy individuals. Strikingly, infection with human cytomegalovirus (CMV), but not with other common herpesviruses, induced expansion and differentiation of KIR-expressing NK cells, visible as stable imprints in the repertoire. Education by inhibitory KIRs promoted the clonal-like expansion of NK cells, causing a bias for self-specific inhibitory KIRs. Furthermore, our data revealed a unique contribution of activating KIRs (KIR2DS4, KIR2DS2, or KIR3DS1), in addition to NKG2C, in the expansion of human NK cells. These results provide new insight into the diversity of KIR repertoire and its adaptation to virus infection, suggesting a role for both activating and inhibitory KIRs in immunity to CMV infection.

Introduction to the immune system

The immune system in a broad sense is a mechanism that allows a living organism to discriminate between "self" and "non-self." Examples of immune systems occur in multicellular organisms as simple and ancient as sea sponges. In fact, complex multicellular life would be impossible without the ability to exclude external life from the internal environment. This introduction to the immune system explores the cell types and soluble factors involved in immune reactions, as well as their location in the body during development and maintenance. Additionally, a description of the immunological events during an innate and adaptive immune reaction to an infection is discussed, as well as a brief introduction to autoimmunity and cancer immunity.

Controlling natural killer cell responses: integration of signals for activation and inhibition

Understanding how signals are integrated to control natural killer (NK) cell responsiveness in the absence of antigen-specific receptors has been a challenge, but recent work has revealed some underlying principles that govern NK cell responses. NK cells use an array of innate receptors to sense their environment and respond to alterations caused by infections, cellular stress, and transformation. No single activation receptor dominates; instead, synergistic signals from combinations of receptors are integrated to activate natural cytotoxicity and cytokine production. Inhibitory receptors for major histocompatibility complex class I (MHC-I) have a critical role in controlling NK cell responses and, paradoxically, in maintaining NK cells in a state of responsiveness to subsequent activation events, a process referred to as licensing. MHC-I-specific inhibitory receptors both block activation signals and trigger signals to phosphorylate and inactivate the small adaptor Crk. These different facets of inhibitory signaling are incorporated into a revocable license model for the reversible tuning of NK cell responsiveness.

Understanding natural killer cell regulation by mathematical approaches

The activity of natural killer (NK) cells is regulated by various processes including education/licensing, priming, integration of positive and negative signals through an array of activating and inhibitory receptors, and the development of memory-like functionality. These processes are often very complex due to the large number of different receptors and signaling pathways involved. Understanding these complex mechanisms is therefore a challenge, but is critical for understanding NK cell regulation. Mathematical approaches can facilitate the analysis and understanding of complex systems. Therefore, they may be instrumental for studies in NK cell biology. Here we provide a review of the different mathematical approaches to the analysis of NK cell signal integration, activation, proliferation, and the acquisition of inhibitory receptors. These studies show how mathematical methods can aid the analysis of NK cell regulation.

Sustained effector function of IL-12/15/18-preactivated NK cells against established tumors

Natural killer cell (NK cell)-based immunotherapy of cancer is hampered by the transient effector function of NK cells. Recently, mouse IL-12/15/18-preactivated NK cells were shown to persist with sustained effector function in vivo. Our study investigated the antitumor activity of such NK cells. A single injection of syngeneic IL-12/15/18-preactivated NK cells, but neither naive nor IL-15- or IL-2-pretreated NK cells, combined with irradiation substantially reduced growth of established mouse tumors. Radiation therapy (RT) was essential for the antitumor activity of transferred NK cells. IL-12/15/18-preactivated NK cells expressed high levels of IL-2Rα (CD25), and their rapid in vivo proliferation depended on IL-2 produced by CD4+ T cells. IL-12/15/18-preactivated NK cells accumulated in the tumor tissue and persisted at high cell numbers with potent effector function that required the presence of CD4+ T cells. RT greatly increased numbers and function of transferred NK cells. Human IL-12/15/18-preactivated NK cells also displayed sustained effector function in vitro. Our study provides a better understanding for the rational design of immunotherapies of cancer that incorporate NK cells. Moreover, our results reveal an essential role of CD4+ T cell help for sustained antitumor activity by NK cells linking adaptive and innate immunity.

Cellular immunity in ASFV responses

African swine fever virus (ASFV) infection usually results in an acute haemorrhagic disease with a mortality rate approaching 100% in domestic pigs. However, pigs can survive infection with less-virulent isolates of ASFV and may become chronically infected. Surviving animals are resistant to challenge with homologous or, in some cases, closely related isolates of the virus indicating that pigs can develop protective immunity against ASFV. During asymptomatic, non-virulent ASFV infections natural killer cell activity increases in pigs, suggesting this cell type plays a role in ASFV immunity. Furthermore, depletion of CD8(+) lymphocytes from ASFV immune pigs demolishes protective immunity against related virulent viruses. This suggests that ASFV specific antibody alone is not sufficient for protection against ASFV infection and that there is an important role for the CD8(+) lymphocyte subset in ASFV protective immunity. These results were supported by DNA immunization studies, demonstrating a correlation between the protection afforded against lethal challenge and the detection of a large number of vaccine-induced antigen-specific CD8(+) T-cells. Peripheral blood mononuclear cells (PBMCs) from ASF immune pigs protected from clinical disease show higher proportions of ASFV specific CD4(+)CD8(high+) double positive cytotoxic T cells than PBMCs from ASF immune but clinically diseased pig. The frequency of ASFV specific IFNγ producing T cells induced by immunization correlates to the degree of protection from ASFV challenge, and this may prove to be a useful indicator of any potential cross-protection against heterologous ASFV isolates.

Mapping of NKp46(+) Cells in Healthy Human Lymphoid and Non-Lymphoid Tissues

Understanding Natural Killer (NK) cell anatomical distribution is key to dissect the role of these unconventional lymphocytes in physiological and disease conditions. In mouse, NK cells have been detected in various lymphoid and non-lymphoid organs, while in humans the current knowledge of NK cell distribution at steady state is mainly restricted to lymphoid tissues. The translation to humans of findings obtained in mice is facilitated by the identification of NK cell markers conserved between these two species. The Natural Cytotoxicity Receptor (NCR) NKp46 is a marker of the NK cell lineage evolutionary conserved in mammals. In mice, NKp46 is also present on rare T cell subsets and on a subset of gut Innate Lymphoid Cells (ILCs) expressing the retinoic acid receptor-related orphan receptor γt (RORγt) transcription factor. Here, we documented the distribution and the phenotype of human NKp46⁺ cells in lymphoid and non-lymphoid tissues isolated from healthy donors. Human NKp46⁺ cells were found in splenic red pulp, in lymph nodes, in lungs, and gut lamina propria, thus mirroring mouse NKp46⁺ cell distribution. We also identified a novel cell subset of CD56^dimNKp46^low cells that includes RORγt⁺ ILCs with a lineage⁻CD94⁻CD117^brightCD127^bright phenotype. The use of NKp46 thus contributes to establish the basis for analyzing quantitative and qualitative changes of NK cell and ILC subsets in human diseases.

Loss of kindlin-3 alters the threshold for NK cell activation in human leukocyte adhesion deficiency-III

Recent evidence suggests that kindlin-3 is a major coactivator, required for most, if not all, integrin activities. Here we studied the function of kindlin-3 in regulating NK cell activation by studying a patient with kindlin-3 deficiency (leukocyte adhesion deficiency-III). We found that kindlin-3 is required for NK cell migration and adhesion under shear force. Surprisingly, we also found that kindlin-3 lowers the threshold for NK cell activation. Loss of kindlin-3 has a pronounced effect on NK cell-mediated cytotoxicity triggered by single activating receptors. In contrast, for activation through multiple receptors, kindlin-3 deficiency is overcome and target cells killed. The realization that NK cell activity is impaired, but not absent in leukocyte adhesion deficiency, may lead to the development of more efficient therapy for this rare disease.

IL-17-producing innate lymphoid cells are restricted to mucosal tissues and are depleted in SIV-infected macaques

Innate lymphoid cells (ILCs) are an emerging subset of lymphocytes involved in surveillance against virally infected cells. Here, we show CD3(-)CD8(high) lymphocytes in macaque blood include major subsets of ILCs including natural killer (NK) cells expressing CD16, NKp46, and NKG2A, but also populations of ILCs in mucosal tissues having different properties. One ILC subset secreted interleukin (IL)-17 (ILC17), but these were restricted to mucosal tissues. Some mucosal ILC17 cells expressed classical NK-cell markers, but little NKG2A or NKG2D. Some ILC17 cells secreted IL-22 and tumor necrosis factor-α, but few produced interferon (IFN)-γ or contained granzyme B. IL-17 production by ILCs was induced by IL-6, transforming growth factor-β, and IL-23. Further, simian immunodeficiency virus (SIV) infection resulted in a significant loss of ILC17 cells, especially in the jejunum, which persisted throughout SIV infection. These findings indicate that ILC17 cells may be involved in innate mucosal immune responses, and their loss may contribute to loss of intestinal mucosal integrity and disease progression in human immunodeficiency virus (HIV)/SIV infection.

Is interferon-gamma the right marker for bacille Calmette-Guérin-induced immune protection? The missing link in our understanding of tuberculosis immunology

Bacille Calmette-Guérin (BCG), developed a century ago, is the only licensed tuberculosis (TB) vaccine in use to date. The protective efficacy of BCG against TB varies with no apparent protection in some population, and mechanisms of its immune protection is poorly known, and yet BCG is the most widely used vaccine, with more than 4 billion BCG-vaccinated children globally. BCG is probably the only licensed vaccine currently in use believed to mediate immune protection through the production of interferon (IFN)-γ by CD4 T cells, which in turn activates macrophages to kill Mycobacterium tuberculosis (Mtb). Currently, a number of new TB candidate vaccines are in different phases of clinical trial. The majority of these new vaccines are either recombinant forms of BCG or prime boosters of BCG (rBCG) and their immunogenicity is tested using BCG as a benchmark by measuring specific IFN-γ produced by CD4(+) T cells as a protective immune marker. However, some recent studies that examined mechanisms of immune protection of BCG in animals and humans have reported a lack of correlation between IFN-γ production by CD4 cells and BCG-induced immune protection. These studies point to the fact that there is a missing link in our understanding of TB immunology. Conversely, there is emerging evidence that other T cell subsets (gammadelta, γδ), CD8(+) T cells and natural killer (NK) cells may play a vital role in immune protection against Mtb infection and BCG-induced immune protection. γδ T cells and NK cells, which were considered to be part of the innate immunity in the past, have been shown to develop immunological memory upon re-encounter with the same pathogen. In this paper, the controversy over the role of IFN-γ as a marker for protective immunity against TB, and emerging data on the role of γδ T cells, CD8(+) and NK cells in TB immunology, will be presented.

Innate immune activation in obesity

The innate immune system is a prewired set of cellular and humoral components that has developed to sense perturbations in normal physiology and trigger responses to restore the system back to baseline. It is now understood that many of these components can also sense the physiologic changes that occur with obesity and be activated. While the exact reasons for this chronic immune response to obesity are unclear, there is strong evidence to suggest that innate inflammatory systems link obesity and disease. Based on this, anti-inflammatory therapies for diseases like type 2 diabetes and metabolic syndrome may form the core of future treatment plans. This review will highlight the components involved in the innate immune response and discuss the evidence that they contribute to the pathogenesis of obesity-associated diseases.

Rag1-/- mutant zebrafish demonstrate specific protection following bacterial re-exposure

Background

Recombination activation gene 1 deficient (rag1^−/−) mutant zebrafish have a reduced lymphocyte-like cell population that lacks functional B and T lymphocytes of the acquired immune system, but includes Natural Killer (NK)-like cells and Non-specific cytotoxic cells (NCC) of the innate immune system. The innate immune system is thought to lack the adaptive characteristics of an acquired immune system that provide enhanced protection to a second exposure of the same pathogen. It has been shown that NK cells have the ability to mediate adaptive immunity to chemical haptens and cytomegalovirus in murine models. In this study we evaluated the ability of rag1^−/− mutant zebrafish to mount a protective response to the facultative intracellular fish bacterium Edwardsiella ictaluri.

Methodology/Principal Findings

Following secondary challenge with a lethal dose of homologous bacteria 4 and 8 weeks after a primary vaccination, rag1^−/− mutant zebrafish demonstrated protective immunity. Heterologous bacterial exposures did not provide protection. Adoptive leukocyte transfers from previously exposed mutants conferred protective immunity to naïve mutants when exposed to homologous bacteria.

Conclusions/Significance

Our findings show that a component of the innate immune system mounted a response that provided significantly increased survival when rag1^−/− mutant zebrafish were re-exposed to the same bacteria. Further, adoptive cell transfers demonstrated that kidney interstitial leukocytes from previously exposed rag1^−/− mutant zebrafish transferred this protective immunity. This is the first report of any rag1^−/− mutant vertebrate mounting a protective secondary immune response to a bacterial pathogen, and demonstrates that a type of zebrafish innate immune cell can mediate adaptive immunity in the absence of T and B cells.

Models and methods for analysis of lymphocyte repertoire generation, development, selection and evolution

T and B cell receptor repertoires are diversified by variable region gene rearrangement and selected based on functionality and lack of self-reactivity. Repertoires can also be defined based on phenotype and function rather than receptor specificity - such as the diversity of T helper cell subsets. Natural killer (NK) cell repertoires, in which each cell expresses a randomly chosen subset of its inhibitory receptor genes, and is educated based on self-MHC recognition by yet unknown mechanisms, are also phenotypic repertoires. Studying the generation, development and selection of lymphocyte repertoires, and their functions during immune responses, is essential for understanding the function of the immune system in healthy individuals and in immune deficient, autoimmune or cancer patients. The study of lymphocyte repertoires will enable clinical immunologists to develop better therapeutic monoclonal antibodies, vaccines, transplantation donor-recipient matching protocols, and other immune intervention strategies. The recent development of high-throughput methods for repertoire data collection - from multicolor flow cytometry through single-cell imaging to deep sequencing - presents us now, for the first time, with the ability to analyze and compare large samples of lymphocyte repertoires in health, aging and disease. The exponential growth of these datasets, however, challenges the theoretical immunology community to develop methods for data organization and analysis. Furthermore, the need to test hypotheses regarding immune function, and generate predictions regarding the outcomes of medical interventions, necessitates the development of complex mathematical and computational models, covering processes on multiple scales, from the genetic and molecular to the cellular and system scales.

Innate immunity in the control of HIV/AIDS: recent advances and open questions

From the publication of the first AIDS issue onwards, major advances have been made in the field of innate immunity during HIV infection. Innate immunity can be defined as the first and unspecific lines of defense constitutively present and ready to be mobilized upon infection. Although a large body of literature adamantly highlights that innate immunity is a critical weapon of defense against HIV and its simian parents (simian immunodeficiency virus, SIV), innate immunity is still underexplored. Focusing on innate immunity may open new paths for the development of innovative therapeutics and vaccine strategies against HIV. Understanding innate immunity may shed light on the natural protection occurring in rare HIV-1-infected individuals who control their infection. This review focuses on innate mechanisms sensing HIV-1 entry and controlling HIV-1 infection, as well as promoting inflammation and shaping adaptive immunity.

Viral quasispecies evolution

Evolution of RNA viruses occurs through disequilibria of collections of closely related mutant spectra or mutant clouds termed viral quasispecies. Here we review the origin of the quasispecies concept and some biological implications of quasispecies dynamics. Two main aspects are addressed: (i) mutant clouds as reservoirs of phenotypic variants for virus adaptability and (ii) the internal interactions that are established within mutant spectra that render a virus ensemble the unit of selection. The understanding of viruses as quasispecies has led to new antiviral designs, such as lethal mutagenesis, whose aim is to drive viruses toward low fitness values with limited chances of fitness recovery. The impact of quasispecies for three salient human pathogens, human immunodeficiency virus and the hepatitis B and C viruses, is reviewed, with emphasis on antiviral treatment strategies. Finally, extensions of quasispecies to nonviral systems are briefly mentioned to emphasize the broad applicability of quasispecies theory.

Human papillomavirus immunization is associated with increased expression of different innate immune regulatory receptors

Human papillomavirus (HPV) is able to inhibit the secretion of gamma interferon (IFN-γ) and the expression of some immune innate cell receptors. Immunoglobulin-like transcript 2 (ILT2) is a regulatory receptor that seems to participate in the pathogenesis of viral infections. We have studied the expression and function of ILT2 and the expression of other NK cell receptors in 23 healthy women before and after immunization with the quadrivalent HPV (type 6/11/16/18) vaccine (Gardasil). Receptor expression was analyzed by flow cytometry in freshly isolated peripheral blood mononuclear cells as well as after in vitro stimulation with the quadrivalent HPV (type 6/11/16/18) vaccine. In addition, the regulatory function of ILT2 on cell proliferation and IFN-γ production was analyzed. We found a significant increase in the expression of ILT2 by NK and CD3(+) CD56(+) lymphocytes and monocytes after quadrivalent HPV (type 6/11/16/18) vaccine immunization. In addition, the in vitro stimulation with the quadrivalent HPV (type 6/11/16/18) vaccine also increased the proportion of CD3(-) CD56(+) ILT2(+) NK cells. Although the inhibitory function of ILT2 on cell proliferation was enhanced after HPV immunization, the in vitro engagement of this receptor did not affect the synthesis of IFN-γ induced by HPV. Finally, a significant increase in the expression of NKG2D, NKp30, and NKp46 by NK and CD3(+) CD56(+) lymphocytes was detected after quadrivalent HPV (type 6/11/16/18) vaccine immunization. Our data indicate that HPV immunization is associated with significant changes in the expression and function of different innate immune receptors, including ILT2, which may participate in the protective effect of HPV vaccines.

Proinflammatory cytokine signaling required for the generation of natural killer cell memory

Although natural killer (NK) cells are classified as innate immune cells, recent studies demonstrate that NK cells can become long-lived memory cells and contribute to secondary immune responses. The precise signals that promote generation of long-lived memory NK cells are unknown. Using cytokine receptor-deficient mice, we show that interleukin-12 (IL-12) is indispensible for mouse cytomegalovirus (MCMV)-specific NK cell expansion and generation of memory NK cells. In contrast to wild-type NK cells that proliferated robustly and resided in lymphoid and nonlymphoid tissues for months after MCMV infection, IL-12 receptor-deficient NK cells failed to expand and were unable to mediate protection after MCMV challenge. We further demonstrate that a STAT4-dependent IFN-γ-independent mechanism contributes toward the generation of memory NK cells during MCMV infection. Understanding the full contribution of inflammatory cytokine signaling to the NK cell response against viral infection will be of interest for the development of vaccines and therapeutics.

Natural killer cell lines in tumor immunotherapy

Natural killer (NK) cells are considered to be critical players in anticancer immunity. However, cancers are able to develop mechanisms to escape NK cell attack or to induce defective NK cells. Current NK cell-based cancer immunotherapy is aimed at overcoming NK cell paralysis through several potential approaches, including activating autologous NK cells, expanding allogeneic NK cells, usage of stable allogeneic NK cell lines and genetically modifying fresh NK cells or NK cell lines. The stable allogeneic NK cell line approach is more practical for quality-control and large-scale production. Additionally, genetically modifying NK cell lines by increasing their expression of cytokines and engineering chimeric tumor antigen receptors could improve their specificity and cytotoxicity. In this review, NK cells in tumor immunotherapy are discussed, and a list of therapeutic NK cell lines currently undergoing preclinical and clinical trials of several kinds of tumors are reviewed.

Wild mice provide insights into natural killer cell maturation and memory

The immune system has evolved, and continues to evolve, in response to the selection pressure that infections exert on animals in their natural environments, yet much of our understanding about how the immune system functions comes from studies of model species maintained in the almost complete absence of such environmental selection. The scientific discipline of immunology has among its aims the improvement of human and animal health by the application of immunological knowledge. As research on humans and domesticated animals is highly constrained-ethically, logistically and financially-experimental animal models have become an invaluable tool for dissecting the functioning of the immune system. The house mouse (Mus musculus) is by far the most widely used animal model in immunological research but laboratory-reared mice provide a very narrow view of the immune system-that of a well-fed and comfortably housed animal with minimal exposure to microbial pathogens. Indeed, so much of our immunological knowledge comes from studies of a very few highly inbred mouse strains that-to all intents and purposes-our immunological knowledge is based on enormously detailed studies of very small numbers of individual mice. The limitations of studies in inbred strains of laboratory mice are well-recognized (Pedersen & Babayan 2011), but serious attempts to address these limitations have been few and far between. However, the emerging field of 'ecological immunology' where free-living populations are studied in their natural habitat is beginning to redress this imbalance (Viney et al. 2005; Martin et al. 2006; Owen et al. 2010; Abolins et al. 2011). As demonstrated in the work by Boysen et al. (2011) in this issue of Molecular Ecology, studies in wild animal populations-especially free-living M. musculus-represent a valuable bridge between studies in humans and livestock and studies of captive animals.

Role of runt-related transcription factor 3 (RUNX3) in transcription regulation of natural cytotoxicity receptor 1 (NCR1/NKp46), an activating natural killer (NK) cell receptor

Natural cytotoxicity receptor 1 (NCR1), also known as NKp46, is a natural killer (NK) lymphocyte-activating receptor. It is involved in major aspects of NK immune function and shows a high degree of lineage specificity in blood and bone marrow. The nature of its NK-restricted expression is not well understood. In this study, we confirm that human NCR1 NK-specific expression is achieved at the mRNA level. We found two key cis-regulatory elements in the immediate vicinity upstream of the gene. One element acts as an essential promoter, whereas the other acts as a tissue-dependent enhancer/repressor. This latter regulatory element contains a runt related-transcription factor (RUNX) recognition motif that preferentially binds RUNX3. Interfering with RUNX proteins using a dominant negative form results in decreased Ncr1 expression. RUNX3 overexpression had the opposite effect. These findings shed light on the role of RUNX3 in the control of an important NK-activating receptor.

BCG vaccination of neonatal calves: potential roles for innate immune cells in the induction of protective immunity

Bovine tuberculosis is a disease of increasing incidence in the UK causing major economic losses and with significant impact on bovine and, potentially human health: the causative agent Mycobacterium bovis is a zoonotic pathogen. Neonatal vaccination with the attenuated M. bovis Bacille Calmette Guerin (BCG) vaccine confers a significant degree of protection in cattle, and is a widely used control strategy for human TB. The adaptive immune system is relatively immature in neonates and increased numbers of innate effector cells present in young animals and human infants may compensate for this, enabling effective immune responses to vaccination. Natural killer cells and subsets of γδ TCR+ T lymphocytes secrete high levels of interferon gamma and can interact with antigen presenting cells to promote both innate and adaptive immune responses. These cell populations may be pivotal in determining immune bias following neonatal vaccination with BCG.

All is fair in virus-host interactions: NK cells and cytomegalovirus

The infection of mice with mouse cytomegalovirus (MCMV) as a model of human cytomegalovirus (HCMV) infection has been particularly informative in elucidating the role of innate and adaptive immune response mechanisms during infection. Millions of years of co-evolution between cytomegaloviruses (CMV) and their hosts has resulted in numerous attempts to overwhelm each other. CMVs devote many genes to modulating the host natural killer (NK) cell response and NK cells employ many strategies to cope with CMV infection. While focusing on these attack-counterattack measures, this review will discuss several novel mechanisms of immune evasion by MCMV, the role of Ly49 receptors in mediating resistance to MCMV, and the impact of the initial NK cell response on the shaping of adaptive immunity.

Use of NK cell activity in cure by transplant

Analogous to T cells, Natural Killer (NK) cells may facilitate engraftment, combat infection, and control cancer in bone marrow or haematopoietic stem cell transplantation (HSCT); however, NK cells do not cause graft-versus-host disease. Killer immunoglobulin-like receptors (KIRs) regulate NK cell function, and recent data suggest that KIR is as important as its ligand (human leucocyte antigen; HLA) in HSCT for both malignant and non-malignant conditions. Because there is substantial variability in KIR gene content, allelic polymorphism, and cell-surface expression among people, careful selection of donors based on HLA and KIR is essential to optimize HSCT outcomes. Furthermore, NK cells may be used for adoptive immunotherapy after HSCT in place of conventional donor lymphocyte infusion, as part of pre-transplant cytoreductive therapy, or as an independent therapeutic agent in high-risk leukaemia in place of sibling donor HSCT.

Understand memory, design better vaccines

Naive lymphocytes have a finite lifespan and are continually replaced by input from generative organs. In contrast, memory cells or their progeny can last a lifetime. The expanded populations of memory cells and their more widespread distribution provide protection against recurrent infection.

Immunological differences in women compared with men: overview and contributing factors

CITATION

Ghazeeri G, Abdullah L, Abbas O. Immunological differences in women compared with men: overview and contributing factors. Am J Reprod Immunol 2011; 66: 163-169 Gender differences in the innate and adaptive immune systems have long been observed in humans. These immunological differences in immune function manifest as diverse susceptibilities to different types of infections and varied risks of developing autoimmune disorders and maybe even, cancers. Several factors contribute to the development of this immunological dimorphism including sex hormones, genetic makeup, environmental causes, and more recently microchimerism. Although the aim behind this sexual immune dimorphism is still unclear, it is tempting to believe that the higher risk of developing autoimmune diseases in women somehow serves the higher evolutionary goal of reproduction and creating new life.