Therapeutic effects of antibodies to interleukin-5

Human eosinophils produce neurotrophins and secrete nerve growth factor on immunologic stimuli

Neurotrophins, such as nerve growth factor (NGF) and neurotrophin-3 (NT-3), are essential for development, function, and survival of peripheral sympathetic and sensory neurons. Most eosinophilic leukocytes in the human body are localized in mucosal tissues; however, the roles of eosinophils in human diseases are not fully understood. We found that human eosinophils constitutively express messenger RNA for NGF and NT-3, synthesize and store these proteins intracellularly, and continuously replenish them. Incubation of eosinophils with a transcription inhibitor, actinomycin D, for 8 hours completely depletes intracellular NGF and NT-3. New synthesis of NGF is enhanced by Fc-receptor-mediated stimuli, such as immunoglobulin (Ig)A and IgG immune complexes; in contrast, production of NT-3 is not affected by these stimuli. Notably, supernatants of eosinophils stimulated with IgA immune complex and interleukin 5 promote neurite extension of the PC-12 pheochromocytoma cell line; this effect is abolished by pretreatment of the supernatants with anti-NGF-neutralizing antibody. By enzyme-linked immunosorbent assay, substantial amounts of NGF protein are also detected in the supernatants of stimulated eosinophils. Furthermore, in patients with seasonal allergic rhinitis, the concentrations of NGF in nasal secretions correlate with the magnitudes of eosinophilic inflammation in the airway, suggesting a potential clinical implication of eosinophil NGF. Our observations propose a new pathologic mechanism by which eosinophils may contribute to enhanced neurologic responses in patients with allergic diseases and other eosinophilic disorders. Alternatively, eosinophils may play important roles in maintenance and restoration of homeostatic functions of mucosal tissues through the pleitropic activities of NGF.

Evidence-based treatment of allergic rhinitis

Allergic rhinitis is an extremely common disease worldwide, affecting 10% to 50% of the population. An increasing prevalence of allergic rhinitis over the past decades and its frequent association with asthma have raised concerns about treating the disease appropriately. New knowledge of the pathophysiologic mechanisms underlying allergic inflammation of the airways has resulted in the development of newer and better therapeutic strategies. This review focuses on evidence-based treatment of allergic rhinitis, highlighting the most recent international consensus and evidence-based guidelines on allergic rhinitis.

Contributing factors to the pathobiology of asthma. The Th1/Th2 paradigm

CD4+ "helper" T-lymphocytes in murine and human models have been divided into Th1 and Th2 subclasses, characterized by the profile of cytokines they secrete: INF-gamma (and perhaps IL-2 and TNF-beta) by Th1 cells, and IL-4 (and perhaps IL-5, IL-6, IL-10, and IL-13) by Th2 cells. Although a strict division into Th1 and Th2 phenotypes in humans (unlike murine systems) may not be possible, the asthmatic diathesis in humans appears to be one largely characterized by inflammatory responses associated with Th2 cells and their cytokines, particularly IL-4, IL-13, and IL-5. Other pulmonary disorders, such as those associated with infectious diseases including tuberculosis, appear to favor an immunologic response characteristic of Th1-cells, and its defining cytokine IFN-gamma. This apparent Th1/Th2 immune dysregulation in asthma is an area of active investigation and forms the basis for ongoing attempts to change this phenotype through a variety of approaches. These include immunotherapy with conventional antigens, designer peptides, oligonucleotides, and anti-IgE, and pharmacotherapy with immune modulating drugs, cytokines, cytokine agonists and cytokine antagonists, and antibodies. This field of investigation promises to usher in a whole new approach to our understanding of asthma and ways to approach its treatment.