Opinion Article - Journal of Clinical Pathology and Laboratory Medicine (2023) Volume 5, Issue 1
Inflammatory bowel disease's immunopathology.
Department of Biological Sciences, Vanderbilt University, USA.
- *Corresponding Author:
- Frank Willing
Department of Biological Sciences
Received:27-Dec-2022, Manuscript No. AACPLM-23-85970; Editor assigned:30-Dec-2022, PreQC No. AACPLM-23-85970(PQ); Reviewed:13-Jan-2023, QC No. AACPLM-23-85970; Revised:18-Jan-2023, Manuscript No. AACPLM-23-85970(R); Published:25-Jan-2023, DOI:10.35841/aacplm-5.1.132
Citation: Willing F. Inflammatory bowel disease's immunopathology. J Clin Path Lab Med. 2023;5(1):132
The immune system, the environment, and susceptibility genes interact in a complicated series of ways that lead to inflammatory bowel disease (IBD). Fungus and the host microbiome all contribute significantly to the onset of IBD, either directly by inducing inflammation or indirectly through changes in the immune system. Researchers can now quantify the diverse microbiome components, which will enable further advancements in the understanding of the genesis of IBD. Intestinal epithelial cells, innate lymphoid cells, cells of the innate and adaptive (T-cells and B-cells) immune systems, and their secreted mediators are some of the mucosal immune system components that are implicated in the pathogenesis of IBD. The activation of the innate immune system may be mediated by increased toll-like receptor activity and results from either a mucosal vulnerability or a failure in the sampling of gut luminal antigen, presumably through the process of autophagy. Naive T-cells are subsequently mediated by the antigen-presenting cells to differentiate into effector T helper (Th) cells, such as Th1, Th2, and Th17, which disru pt gut homeostasis and cause IBD.
T helper (Th) cells, Inflammatory Bowel Disease (IBD), Immunopathology, and Crohn’s Disease.
With alternating episodes of clinical relapse and remission, inflammatory bowel disease (IBD) is a chronic inflammatory condition that includes both Crohn's Disease (CD) and Ulcerative Colitis (UC). In addition to exhaustion, chronic diarrhoea with or without extensive bleeding, abdominal pain, weight loss, and fever, CD can affect any region of the gastrointestinal tract. UC typically affects the colon and manifests as lower abdominal pain, tenesmus, rectal bleeding, frequent faeces, and mucus discharge from the rectum. In the context of a genetically vulnerable person, a dysregulated immune system is assumed to be the cause of IBD. IBD currently affects a large number of people, with a prevalence rate of 396 per 100,000 persons worldwide. The prevalence of CD is thought to be 5 per 100,000 people in the US, and it is characterised by localised and transmural inflammation that can happen anywhere along the length of the gastrointestinal tract, including B2 structuring, B3 penetrating, and even perianal illness. UC, which affects 8–12 per 100,000 people, is characterised by colonic mucosal inflammation that extends across the entire colon and involves the rectum. Additionally, individuals with IBD are more likely to develop psoriasis and primary sclerosing cholangitis than people without the condition.
The growth and control of the immune system as well as defence against the invasion of harmful bacteria depend heavily on host-microbe interactions. The innate immune system, which is comprised of mucin, the epithelium, and innate immune system cells in the gut, is the body's first line of defence against harmful organisms. It's interesting to note that animals with severe combined immunodeficiency and recombinase activation gene deficiency, which lack an adaptive immune system but have a functioning innate immune system, do not spontaneously develop colitis and coexist with the microbiota. However, when DSS, an anti-CD40 antibody, and an infection with Helicobacter hepaticas are combined, these mice can develop colitis.
As a defence against a variety of infectious pathogens, the immune system has developed. The immune system in vertebrates can be generally split into the innate immune system and the adaptive immune system. The innate immune system serves as the body's initial line of defence against infections and offers a quick protective reaction. It also aids in the start of the adaptive immune response. Innate immunity is non-specific and does not provide long-lasting protection. The innate immune system is made up of the epithelial barrier, eosinophils, basophils, macrophages, monocytes, neutrophils, DCs, and natural killer cells. Through the release of cytokines, chemokines, and antimicrobials, these cells work in concert to start an inflammatory response. As a result, infected cells and bacteria are phagocytosed, antigens are presented, and the adaptive immune system is activated.
Lymphocytes, which are a component of the adaptive immune response, produce effector responses when activated. The adaptive immune system is extremely specialised and provides long-lasting immunity, in contrast to the innate immune system. It is generally believed that the adaptive immune system, either through increased pro-inflammatory cytokines produced by the T-helper (Th) subsets or by inadequate anti-inflammatory regulatory T-cells, is the primary contribution to disease pathogenesis in IBD (Tregs). After activation, naive T-cells (Th0) can develop into Th1, Th2, or Th17 cells. The pathogenesis of CD has been specifically linked to Th1 responses, whereas the pathogenesis of UC has been linked to Th2 responses.
When stimulated by cytokines and bacteria, monocytes, macrophages, DCs, fibroblasts, and endothelial cells express the membrane-bound or secreted protein TL1A, which is encoded by the tumour necrosis factor super family 15 (TNSF15). It binds to the death domain receptor 3 (DR3), which is mostly expressed on T cells, to start a variety of immunological reactions, such as activating T cells that release pro-inflammatory mediators. Asthma, rheumatoid arthritis, and inflammatory bowel disease (IBD) are just a few of the autoimmune disorders that TL1A has been linked to as a pathogen. The idea that TL1A is a key regulator of mucosal inflammation at the boundary between the innate and adaptive immune system has received a lot of support from research.
New Th cell subsets, including follicular helper T-cells, IL-22-producing Th22 cells, IL-9-producing Th9 cells, and developing kinds of Treg cells, are now being linked to the pathogenesis of inflammatory bowel disease (IBD). Additionally, it was often believed that terminally differentiated T cells seldom underwent re-differentiation into other T cell subsets; nevertheless, the plasticity of T cells is currently the subject of substantial research. The importance of the adaptive immune system in the initiation and maintenance of the inflammatory cascade in Inflammatory Bowel Disease (IBD) has been well established. T-cells in particular have been found to play a significant role in promoting intestinal inflammation. To create effective and useful therapy strategies, nevertheless, a number of unresolved problems must be addressed. The significance of the innate immune system in the pathobiology of IBD has been made clear by recent developments. Chemicals that target certain T-cell derived molecules have mainly failed save from anti-TNF drugs. This demonstrates how unique each person's immune system is in the setting of their own genetics and is probably owing to the complexity and redundancy of cytokine networks. Intestinal microbiota interactions, interactions between various innate and adaptive immune system components, and how these interactions relate in the heavily influenced context of an individual's genetics are areas that will open new horizons in our understanding of the mechanisms of gut inflammation.
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