O’Regan. immune system are important for the initiation of type 2 immunity, which characterises the response to helminth contamination, as well as allergic reactions. The key players in T helper (Th) 2-type immunity are CD4+Th2 cells and involve the cytokines interleukin (IL-)4, IL-5, IL-9, IL-10, and IL-13 and immunoglobulin (Ig)E. CD4+Th2 cells also express some of the cytokines mentioned above as well as the chemokine ligand CCL11 and the chemokine receptor CCR3 [13]. These factors lead to recruitment and infiltration of eosinophils, basophils and mast cells, and expansion of alternatively activated macrophages [4]. Notably, Th2-type immune responses are composed of three major features: inflammation, wound repair, and, most importantly, resistance to helminths. Parasites have developed various strategies to modulate the immune system and ultimately suppress host protective Th2-type immune responses for example, by induction of innate and adaptive regulatory cells, anti-inflammatory cytokines and Rabbit Polyclonal to PDRG1 specific inhibitory antibody isotypes (reviewed by Anthony et al. [2]). Hence, helminth parasites are master regulators of immune responses in order to make sure life-long persistence in the host. One strategy of immune regulation that Cyanidin chloride has evolved is the secretion of Cyanidin chloride a wide range of immunoregulatory molecules, which are able to target various host cells and alter them to induce a highly directed host response known as a modified Th2-type response. This response is designed to limit a possibly detrimental Th2 immune response, thus restraining the extreme symptoms that are often observed in allergy or in aspects of helminth diseases such as fibrosis inSchistosoma mansoni[3]. In immunological terms, the modified Th2 response is usually defined by the development of specific antibody isotypes, including induction of IgG4 accompanied by a decrease in IgE, as well as IL-4 and IL-5, while IL-10 levels from different regulatory cell sources increase [5]. These mechanisms can lead to attenuation of pathology and clinical symptoms, tolerance, and ultimately persistence of the worm, which is associated with a hyporesponsive immune system. Asymptomatic contamination assures long-term survival of the parasite within the host and therefore sustains parasite feeding, completion of the life cycle, and successful reproduction [3,5]. Many studies of animal and human helminth infections have shown their potential for downregulating the Cyanidin chloride immune system. Moreover, relevant epidemiological studies have observed that helminth-infected populations exhibit lower levels of Cyanidin chloride immunopathological diseases such as Th1-related autoimmune diseases or abberrant Th2-related diseases for example, asthma or allergic rhinitis. These observations indicate an inverse global distribution of allergy/autoimmune diseases and helminth infections, the first being an expanding problem of developed and industrialized countries, while the latter being a feature in developing countries [69]. Such findings support the hypothesis that this immune system has coevolved to operate in the presence of immunomodulatory helminth infections, while in the absence of exposure to helminths, the immunoregulatory components that would normally prevent allergy and autoimmune disease become weakened [5,10]. Here, we focus on recent advances in cellular mechanisms that are employed and modulated during helminth infections as well as on reports from field research and studies on animal models. These studies have identified helminths and helminth-derived products that play a role either in induction of Th2 responses and immune modulation in parasitic infections (reviewed inTable 1) or in downregulation of bystander Th2-type immunopathologies like allergic asthma, allergic inflammation and airway hyperreactivity, food allergy, eczema, atopic dermatitis (Th1/Th2), or anaphylaxis (reviewed inTable 2). == Table 1. == Helminth-derived immunomodulatory and Th2-inducing molecules. CXCL: chemokine ligand; DC: dendritic cell; Ig: immunoglobulin; GI: gastrointestinal; IFN-: interferon gamma; IL: interleukin; LPS: lipopolysaccharide; MAP: mitogen activated kinase; MHC: major histocompatibility complex; MIF: macrophage migration inhibitory factor; PBMC: peripheral blood mononuclear cell; STAT: signal transducer and activator of transcription; TGF: transforming growth factor; Th: T helper cell; TLR: Toll-like receptor; Treg: T regulatory cell. == Table 2. == Effects of helminth infections and helminth-derived products/molecules on improvement of symptoms in allergy-related experimental animal models. 1(AI): airway inflammation, associated with inflammatory cell influx into the lungs and local Th2 cytokine production. 2(AHR): airway hyperreactivity, mainly described as lung bronchiole and smooth-muscle tissue remodelling leading to airflow obstruction, resulting in altered airway function. Chronic airway inflammation may lead to AHR, however, different immunopathological pathways govern the regulation of AI and AHR (discussed elsewhere [8993]). 3NA data not available. == 2. Epidemiological Evidence of.