3,817 research outputs found
Distribution of TT virus (TTV), TTV-like minivirus, and related viruses in humans and nonhuman primates
No full textTT virus (TTV) and TTV-like minivirus (TLMV) are small DNA viruses with single-stranded, closed circular, antisense genomes infecting man. Despite their extreme sequence heterogeneity (>50%), a highly conserved region in the untranslated region (UTR) allows both viruses to be amplified by polymerase chain reaction (PCR). TTV/TLMV infection was detected in 88 of 100 human plasma samples; amplified sequences were differentiated into TTV and TLMV by analysis of melting profiles, showing that both viruses were similarly prevalent. PCR with UTR primers also detected frequent infection with TTV/TLMV-related viruses in a wide range of apes (chimpanzees, gorillas, orangutans, gibbons) and African monkey species (mangabeys, drills, mandrills). These findings support the hypothesis for the co-evolution of TTV-like viruses with their hosts over the period of primate speciation, potentially analogous to the evolution of primate herpesviruses
New players in the cytokine orchestra of inflammatory bowel disease
No full textIn both Crohn's disease (CD) and ulcerative colitis, the pathologic process is almost certainly driven by an aberrant local immune response directed against normal components of the bacterial microflora. Mucosal immune cells interact with nonimmune cells such as epithelial cells and fibroblasts to promote tissue damage; cytokines are essential mediators of this cross talk. Accumulating evidence now suggests that interleukin-21 (IL-21), the newest member of the common gamma-chain-dependent cytokine family, is a key component of the inflammatory cascade. IL-21 is highly produced by activated CD4+ lymphocytes in the inflamed gut of patients with CD, where it contributes to sustaining the ongoing Th1 inflammation. IL-21 also increases the secretion of extracellular matrix-degrading enzymes by fibroblasts and of MIP-3α by epithelial cells. Two other cytokines, IL-27 and IL-32, may also be important in the inflammatory pathways that operate in IBD
IL-21 comes of age as a regulator of effector T cells in the gut
No full textIn healthy individuals, antigens from the gut lumen are tolerated by the mucosal immune system. However, a loss of tolerance toward the bacterial microflora probably causes inflammatory bowel disease (IBD), Crohn's disease (CD) and ulcerative colitis. The abnormal activation of the immune system in the gut of IBD patients is characterized by a cascade of cellular events orchestrated by cytokine cross talk between immune and non-immune cells. Interleukin (IL)-21, the newest member of the common γ-chain-dependent cytokine family, is a key component of the inflammatory cascade in the gut. It is highly expressed in CD and sustains the ongoing T helper type 1 (Th1)-mediated immune response. IL-21 is essential for the differentiation of Th17 cells. IL-21 is also involved in recruiting T cells to the inflamed gut and eliciting the secretion of matrix-degrading enzymes by gut fibroblasts. Overall, there is now sufficient evidence to suggest that targeting IL-21 will be of therapeutic benefit in IBD
Immunopathogenesis of Crohn’s disease
No full textThis review highlights the huge advances made in the understanding of Crohn's disease in the last 15 years. The pathogenic immune response in the gut wall is a highly polarised T helper cell type 1 response, probably directed against antigens of the commensal flora. There is marked over-expression of pro-inflammatory cytokines such as tumor necrosis factor (TNF)-alpha and increased production of matrix degrading enzymes by fibroblasts and macrophages, which are probably responsible for ulceration and fistula formation. Crohn's disease runs in families and the susceptibility genes identified so far are associated with innate recognition of microbial products (Nod2) or epithelial barrier function (OCTN cation transporter genes and DLG5). Endogenous healing pathways mediated by transforming growth factor (TGF)-beta1 are inhibited because mucosal inflammatory cells express Smad7, the endogenous intracellular inhibitor of TGF-beta signalling. This makes it unlikely that enteral feeds containing TFG-beta are therapeutic by means of direct anti-inflammatory effects, however TGF-beta may still be involved because it is a well known epithelial motogen and may promote mucosal healing, in synergy with changes in mucosal bacterial populations as a result of the change in the diet
Reprogramming the immune system in IBD
No full textImmune function in the gut mucosa is tightly regulated to prevent deleterious tissue damaging responses to the indigenous microbiota. In animal models, negative regulatory molecules such as transforming growth factor β1 (TGFβ1) and interleukin (IL)-10 seem to be particularly important. Although IL-10 is made by macrophages, T cells and B cells, TGFβ1 is made by many non-lymphoid/myeloid cells, especially epithelial cells. We have been able to show that in the human gut, neutralization of TGFβ1 increases Th1 and Th17 responses. In IBD, however, especially Crohn's disease, exogenous TGFβ1 cannot inhibit inflammation because of a block in intracellular signalling mediated by Smad7. Knockdown of Smad7 allows endogenous TGFβ1 to dampen inflammation in mucosal tissues from Crohn's patients. We have also generated a mouse which over-expresses Smad7 in T cells. This animal develops more severe colitis in a number of different models, but the inflammation helps protect against colon cancer
The pathophysiologic rationale for biological therapies in inflammatory bowel disease
No full textInflammatory bowel disease is driven by an excessive immune response in the gut wall. This review summarises important new developments in understanding this immune response and the downstream mechanisms of intestinal injury, alongside their potential role in opening up new avenues of treatment.
RECENT FINDINGS:
The evidence continues to accumulate that Crohn's disease is primarily due to a T helper cell-type 1 immune response in the gut wall. IL-12 and IL-18 appear to be the cytokines primarily responsible for Th1 polarisation, but IL-21 may also be important. The p40 chain of IL-12 also associates with a novel p19 chain to form IL-23 which is also a potent Th1-inducing cytokine but the expression of IL-23 in Crohn's disease has not been reported. Progress in understanding the immunology of ulcerative colitis remains slow, but IL-13 produced by natural killer T cells may be involved. T-cell resistance to apoptosis occurs in Crohn's disease, and human and mouse studies indicate that the signalling molecule STAT3, which transduces signals from IL-6 and IL-10, is involved in mucosal T cell homeostasis. Fibroblasts and metalloproteinases continue be implicated in ulceration, fibrosis, and fistula formation.
SUMMARY:
Understanding the immunology of inflammatory bowel disease continues to underpin the vast majority of new therapies and identifies new targets. Novel approaches, such as exploiting the antiinflammatory role of cannabinoid receptors, may also prove productive in the future
Informing the conservation process: developing protocols for the application of Raman microspectroscopy to the analysis of pigments and consolidants on painted textiles
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Immunity, inflammation, and allergy in the gut
No full textThe gut immune system has the challenge of responding to pathogens while remaining relatively unresponsive to food antigens and the commensal microflora. In the developed world, this ability appears to be breaking down, with chronic inflammatory diseases of the gut commonplace in the apparent absence of overt infections. In both mouse and man, mutations in genes that control innate immune recognition, adaptive immunity, and epithelial permeability are all associated with gut inflammation. This suggests that perturbing homeostasis between gut antigens and host immunity represents a critical determinant in the development of gut inflammation and allergy
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