In the prepatent phase of infection, larval stages provoke strong

Th2-related responses. In the chronic phase of infection in the gut lumen, excretory secretory products of adult nematodes can stimulate regulatory responses [6-8] leading to hyporesponsiveness of host lymphocytes. The hyporesponsiveness and also inhibition of cell apoptosis may be a consequence of immunosuppression caused by the nematode [9, 10]. As apoptosis is linked to the function and regulation of the immune system, the ability of the parasites to inhibit apoptosis could profoundly alter the immune response [11]. It was suggested that H. polygyrus antigens, which prevented glucocorticoid-induced apoptosis, controlled the number of regulatory T cells (Treg) and apoptosis of both CD4- and CD8-positive T cells [12]. These observations suggest that the parasitic proteome Selleck PARP inhibitor contains immunomodulatory factors responsible for evasion of the host immune response. To better understand the molecular mechanisms that lead to the activation and modulation of the host immune response by H. polygyrus, transcriptome next generation sequencing (RNA-seq) technologies and bioinformatic tools has been already proposed [13] but the nematode proteins that mediate these effects remain largely

unknown. Activation of the immune response generates functionally this website active effector T cells through clonal expansion. Most effector T cells are later eliminated, whereas a small number survive and differentiate into memory T cells. The mechanisms by which some effector T cells escape apoptosis are not understood and little is known about

the factors that regulate the shift from an apoptosis-resistant to an apoptosis-sensitive phenotype. Activation of naive T cells requires an antigen-driven signal accompanied by a signal delivered through costimulatory molecules, both presented on antigen-presenting cell (APC) surface. CD4+ and CD8+ T cells generate antigen-specific responses, which can be retrieved upon antigen rechallenge. Also, Th1 and/or Th2 cells are activated during Ribonucleotide reductase the inflammatory response and CD4+CD25hi T cells differentiate and display regulatory activity [14-16]. Treg cells are critical in establishing and maintaining a peripheral tolerance where reactivity to a specific antigen is actively down-regulated to prevent inappropriate immune responses [17, 18]. Regulation of the lifespan of these cells is important for the outcome of the immune response, especially during prolonged and potentially pathogenic parasitic infection. Programmed cell death is induced by many factors, including tumour necrosis factor TNFα [19], glucocorticoids or through T-cell receptor signalling [20, 21]. There are two main pathways of apoptosis: one pathway involves the interaction of death receptors, such as TNF receptor-1 or Fas receptor with its ligand, the second pathway is regulated by proapoptotic and antiapoptotic members of the Bcl-2 family in mitochondria.