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Battle for Survival: Interplay Between Pathogenic Mycobacteria and the Host Immune System


Promotion of a Down-modulated Lung Immune State May Be a Strategy by M. tuberculosis to Foster Active Disease and Persistence

Abstract: One-third of humans carry Mycobacterium tuberculosis, the etiological agent of tuberculosis (TB) where microbe/host immune response interactions result in persistence or active TB. However, immune mediators associated with human TB remain poorly defined. Through a series of comparative studies of lung immune response of TB cases at the time of diagnosis and patients with other infectious lung diseases and volunteers, we found that TB cases expressed significantly higher levels of mediators that counteract Th1-type and innate immunity critical for containment of M. tuberculosis. Despite the concomitant heightened levels of Th1-type mediators, they are likely rendered ineffectual by high levels of intracellular (e.g., SOCS) and extracellular (e.g., IL-10) immune suppressors. These modulators are a direct response to M. tuberculosis as many suppressive factors declined to the levels of controls by 30 days of anti-TB treatment while most Th1-type and innate immune mediators rose above the pre-treatment levels. Parallel laboratory studies and monitored lung alveolar macrophage effector, nitric oxide synthase-2 (being shown critical for killing M. tuberculosis), support that M. tuberculosis actively promotes down-modulatory mediators to counteract Th1-type/innate immunity as an immunopathological strategy. Our studies highlight the potential application of immune mediators as surrogate markers for TB diagnosis or treatment response. ... Read more

Learning From BCG: Designing a Better Tuberculosis Vaccine

Abstract: Widely used TB vaccine BCG protects children from TB much more effectively than adults. The reason: prior to BCG vaccination, many adults were exposed to Mycobacterium tuberculosis or atypical mycobacterium species such as M. avium and subsequently developed variable levels of cross-immunity against the BCG. For protecting the adult population, a genetically modified BCG vaccine should be explored. ... Read more

Treating Both the Disease and the Patient as a Whole

The concept of treating a diseased patient rather than a patient’s disease is compelling. In light of the fact that many diseases are the combined outcome of both pathogenetic factors and maladjustments in the body, treating both symptoms, underlying causes, and contributing factors should be most effective in achieving both immediate and long-lasting therapeutic results.

An example is tuberculosis, a disease that has millions (an estimated 8.8 millions in 2005 - the latest data available) of new cases worldwide each year. As soon as Mycobacterium tuberculosis enters the body, the battle between the bacteria and the body’s immune system begins. The ... Read more

MicroRNAs Regulate Immune System Via Multiple Targets

Abstract: MicroRNAs (miRNAs) represent the most abundant class of regulators of gene expression. Each miRNA may suppress multiple mRNA targets, while one mRNA can be targeted by many miRNAs for precise control of a wide range of cellular processes. The important role of miRNAs in the immune system is highlighted by the conditional Dicer knockout mouse, which exhibited profound aberrant development and function of immune cells. One particular miRNA, miR-155, is highly expressed and plays important role in lymphocytes. In this review we focused on the role of miRNA, especially miR-155, via their predicted and known mRNA targets in innate and adaptive immunity. Finally, we discussed the potential of miRNAs as novel targets for the diagnosis and therapy of immune system diseases. ... Read more

Advances in Mechanisms of Systemic Lupus Erythematosus

Abstract: Systemic lupus erythematosus (SLE) is a complex autoimmune disease associated with hormonal, environmental, and genetic factors and linked to the tolerance breakdown of B and T cells to self-antigens. SLE is characterized by the presence in patient serum of autoantibodies raised against nuclear components. Association of these antibodies to self-antigens, complement factors, DNA, and particular proteins will form circulating immune complexes (CIC) which can deposit in several organs, causing tissue damage and clinical manifestations. Historically, SLE is considered as an adaptive immune system disorder. Over the past decade, advances in the understanding of SLE pathogenesis placed the innate immune system as a key player in perpetuating and amplifying this systemic disease. In this review, we summarize some recent key advances in understanding the SLE immune-pathogenesis with a particular focus on newly discovered key factors from the innate immune system and how they influence the pathogenic adaptive immune system: neutrophils and neutrophil extracellular traps (NETs), plasmacytoid dendritic cells (pDCs) and type I interferons, basophils and autoreactive IgE, monocytes/macrophages and the inflammasome. Recent advances on B and T cell involvement in the SLE pathogenesis mechanisms are also discussed. Although the disease is clinically, genetically, and immunologically heterogeneous between affected individuals, the latest discoveries are offering new promising therapeutic strategies. ... Read more

Elusive Alzheimer's Disease: Can Immune Signatures Help Our Understanding of This Challenging Disease? Part 2: New Immune Paradigm

Abstract: Alzheimer's disease (AD) is the most common form of dementia. Its most important pathological hallmarks are profound neuronal loss, presence of intracellular neurofibrillary tangles, and extracellular deposition of beta-amyloid protein (Aβ) as beta-amyloid plaques. One of the most important risk factors for AD is age and with the increase of life-expectancy AD has become the most common form of dementia. The current "Holy Grail" is to be able to diagnose variants of AD before they manifest clinically and before irreparable brain damage is done. To be able to do so, we need robust and reliable biomarkers which reflect the pathogenesis of AD. This is essential because such biomarkers might indicate pathways that could be targeted for interventions aiming at disease prevention or amelioration. Although much attention has been focused on Aβ in this respect, it may not be as attractive a target as thought if current doubts concerning its causative role are substantiated. This review will be in two parts, the first part dealt with the current clinical knowledge and the questions raised by the Aβ cascade hypothesis in the pathogenesis of AD and this second part aims to synthesize our current knowledge and new data suggesting how immunity may contribute to the development of AD and may itself be targeted in future treatments. ... Read more

Macrophage Subpopulations in Systemic Lupus Erythematosus

Abstract: Systemic lupus erythematosus (SLE) is a heterogeneous group of autoimmune disorders defined by a consensus of clinical and laboratory criteria. Much of the pathophysiology and therapy of SLE has focused on autoimmune B and T cells of the adaptive immune system. Recently, the role of macrophages, part of the innate immune system, in SLE pathogenesis has gained attention. The field of immunology in general has recently changed in the way that it approaches macrophages. Rather than viewing them as a single, concrete whole, it has become clear that different subpopulations of macrophages contribute to various immune and non-immune processes. Such a nomenclature may provide an ideal framework from which to study macrophage pathogenesis in SLE. Studies suggest that M1 subtype macrophages play an important inflammatory role in SLE pathogenesis. Further, apparently reduced populations of M2a and M2c subtype macrophages may contribute to the lack of anti-inflammatory activity apparent in the disease. M2b subtype macrophages may actually have a role in causing disease directly. Regulatory macrophages have yet to be explored thoroughly in SLE, though the presence of a few of their markers may mean that they are active in suppressing SLE-related inflammation. ... Read more

Point-of-Care Diagnostics for HIV and Tuberculosis: Landscape, Pipeline, and Unmet Needs

Abstract: Early diagnosis and rapid initiation of treatment remains a key strategy to control both HIV and tuberculosis (TB). However, HIV and TB control programs have had completely contrasting successes, especially with the development and deployment of point-of-care (POC) diagnostics. Clinicians, researchers, and public health staff who work at the frontlines of HIV care and control have had access to an outstanding array of POC diagnostics at their disposal, including those used for screening, initial diagnosis, staging, treatment monitoring, and early infant diagnosis. The field has also advanced to consider over-the-counter, self-testing options for HIV and the use of multiplexed platforms that allow for simultaneous detection of infections associated with HIV. In sharp contrast to HIV, suboptimal and delayed diagnosis of TB has perpetuated the epidemic in many high-burden countries. Although the TB diagnostics pipeline is substantially better today than it was even five years ago, absence of a simple POC test continues to be a gaping hole in the pipeline. In this review, we compare the POC diagnostics landscape and pipelines for these two important infectious diseases, and highlight gaps and unmet needs. ... Read more

Vaccine Adjuvant Properties of Probiotic Bacteria

Abstract: Vaccine-preventable diseases are still responsible for the deaths of more than 1 million children under the age of 5 years annually, mostly in developing countries. A substantial number of these deaths are due to pneumococcal bacteria and infections with rotavirus. Important issues faced by the WHO, governments, vaccine manufacturers, and international organizations such as UNICEF and the Global Alliance for Vaccines and Immunization (GAVI) are the cost-effective introduction of these life-saving vaccines in resource-poor countries where there is a considerable disease burden, and achieving high rates of completion of vaccination schedules remains elusive. Problems with vaccine coverage and vaccine delivery in these regions are significant, as in some cases large proportions of the target population do not receive adequate vaccination. Consequently, there is a need to develop more effective vaccination strategies that can provide adequate protection with reduced schedules. To date, emphasis has been placed on identifying novel vaccine antigens and adjuvants that induce stronger protective immune responses, as well as developing mucosally-administered vaccines. These approaches would have enormous benefits in allowing safe administration of vaccines in remote areas and may overcome the necessity for multiple doses. In this regard, the use of probiotic bacteria as novel mucosal adjuvants to enhance existing vaccine specific-immune responses offers an exciting new approach. In this review, we discuss the evidence for the role of probiotics in enhancing vaccine responses and provide justification for further investigation into their clinical effects and mechanisms of action. ... Read more

New Insight in the Mechanism of Action of Rituximab: The Interferon Signature Towards Personalized Medicine

Abstract: Rheumatoid arthritis (RA) is the most common chronic inflammatory disorder of the musculoskeletal system that may cause permanent joint damage. The disease has a major impact on the quality of life of affected individuals, costs for the health care system, and society. Currently, no curative treatment is available, and patients are subjected to a prolonged course of treatment. Due to their role in the pathogenesis of RA, B cells have become an attractive target for therapy. Rituximab (Mabthera®/Rituxan®) is a therapeutic monoclonal antibody against CD20 expressed on B cells, which is effective in depleting B cells and approved worldwide for the treatment of RA. Rituximab was shown to be highly beneficial in decreasing clinical symptoms, safe, and well tolerated. However, clinical experience revealed that approximately 30-40% of RA patients do not respond to it. Given the destructive nature of RA, the risk of adverse effects, and considerable costs for therapy, there is a strong need to make predictions on the clinical outcome before the start of therapy. Since nearly all treated patients experience an effective depletion of circulating B cells, questions have been raised concerning the mechanism of action. In this review, novel developments, in particular the findings on the role of the interferon system, will be highlighted. This may add new and important information to our understanding of the mechanism that underlies the clinical outcome of rituximab treatment and may lead to the identification of biomarkers to predict the response. ... Read more

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