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Cellular and Molecular Basis of Human Biology
Published in Lawrence S. Chan, William C. Tang, Engineering-Medicine, 2019
These mobile proteins are the products of committed B-cells, plasma cells. In human, 5 classes of antibodies are produced: IgM, IgG, IgA, IgE, and IgD. These classes of antibodies are immunologically distinguished by the difference of their heavy chain sequences. As for light chain, only two classes are produced, lambda and kappa chains. In human, IgG has 4 subclasses, IgG1, IgG2, IgG3, and IgG4; whereas IgA has 2 subclasses, IgA1 and IgA2. IgD is a B cell surface receptor and is not usually released into the extracellular environment. Whereas IgM is the initially released antibody response, IgG comes later in the immune response but become the dominant class, constituting 80% of circulating antibodies. IgA is primarily responsible for mucosal immune defense. IgE involves in allergic reaction by binding on IgE receptors of mast cells, triggering mast cells to release histamines.
Basic Chemical Hazards to Human Health and Safety — II
Published in Jack Daugherty, Assessment of Chemical Exposures, 2020
Lymphocytes that produce humoral immunity are called B-cells. Antibodies (Ab) and immunoglobulins (Ig) are proteins on the surface of B-cells. The most abundant immunoglobulin, IgG, from about seven weeks of age onward, produces a secondary response to antigens. Before that age, the infant relies on IgG transferred from its mother transplacentally. IgM primary response antibodies active the complement pathway early in the immune response. IgA is the primary immunoglobulin found in body secretions, such as saliva, tears, and colostrum, and which are the first line of defense in respiratory and gastrointestinal infections. IgD is an important part of B-cell differentiation. IgE attaches to mast cells and other leukocytes.
Nanomedicines for the Treatment of Gastric and Colonic Diseases
Published in Sarwar Beg, Mahfoozur Rahman, Md. Abul Barkat, Farhan J. Ahmad, Nanomedicine for the Treatment of Disease, 2019
Md. Adil Shaharyar, Mahfoozur Rahman, Kainat Alam, Sarwar Beg, Kumar Anand, Chowdhury Mobaswar Hossain, Arijit Guha, Muhammad Afzal, Imran Kazmi, Rehan Abdur Rub, Sanmoy Karmakar
Digestion and absorption are not the only roles played by GI system, but it also shields the internal human body from external pathogens, toxins, and antigens (Farrell et al., 2012). This protective shield has two aspects namely intestinal barrier and intestinal permeability. The intestinal wall is composed of 4 layers namely the mucosa, submucosa, muscularis, and the serosa. The line of distinguishment between the intestinal barrier and permeability lies in the fact that the former is a separation of the gut lumen from the inner host by a functional entity comprising of mechanical elements (mucous and epithelial layer), humoral elements (defensins, IgA), immunological elements (lymphocyte, innate immune cells), muscular, and neurological elements; while the latter is a function of the barrier at specific sites on the intestinal wall. Permeability is measured by flux rate across the intestinal barrier. Impairment of intestinal permeability accounts for the imbalance in intestinal homeostasis (Eberl et al., 2005). Protection of the GI system is maintained by low pH of the gastric acid and enzymes produced by the pancreas. Low pH prevents the bacterial growth, and pancreatic enzyme disrupts the bacterial cell wall. Neutral intragastric pH causes increased the vulnerability of lumen to pathogens like shigella and cholera. Decrease in pancreatic enzymes in pancreatitis has been linked to bacterial growth. Some non-specific barriers involved in the defense mechanism are epithelial crypt cells and villi. The microbes are washed away by the fluid secreted by the epithelial cells along with the help of peristaltic movement. To assist the epithelial cells, the villi secrete mucous which prevent the bacterial adhesion to the receptors on the surface of the epithelial cells. Immunoglobin-A(IgA) and defensins (antimicrobial peptides) are the other non-specific barriers. IgA binds to antigens and increases their intestinal clearance (Ouellette et al., 1997). To add to this, there are some dynamic barriers like cytoskeleton and tight intercellular junctions which allow bidirectional passage of different types of inflammatory cells and substances. Inflammatory cells equip the mucosal defense system by presenting antigen to immune cells. ATP is an essential component of the epithelial system which helps it maintain its integrity and dynamism. Interference in ATP usage causes disruption in the epithelial system. NSAID and Tacrolimus (FK506) interfere with the ATP usage (Gabe et al., 1998; Bjarnason et al., 1993). The immune system safeguards the lumen by taking a sample of the antigen present in that particular area (Mckay et al., 1999). The epithelial barrier disruption is attributed to many inflammatory diseases, weakness of genetic function regulating the barrier (Demeo et al., 2002). Some of the major GI disorders are discussed in the following sections.
The perinatal period, the developing intestinal microbiome and inflammatory bowel diseases: What links early life events with later life disease?
Published in Journal of the Royal Society of New Zealand, 2020
Fathalla Ali, Kei Lui, Alex Wang, Andrew S. Day, Steven T. Leach
IgA is the most abundant immunoglobulin secreted by B cells across the mucus membrane (Macpherson et al. 2012). Most of the IgA producing B cells mature in the gastrointestinal tract upon stimulation by commensal bacteria (Kamada and Nunez 2014). Even though microbiota is crucial for the differentiation of intestinal B cells, different types of bacteria have a different influence on B cell development and IgA production. For example in a germ-free mouse model, intestinal colonisation with SFB resulted in more IgA producing B-cells compared to intestinal colonisation with Clostridia (Umesaki et al. 1999). Furthermore, colonisation with any bacteria results in more IgA producing B-cell compared to no intestinal bacteria (Umesaki et al. 1999).
A complete immunoglobulin-based artificial immune system algorithm for two-stage assembly flowshop scheduling problem with part splitting and distinct due windows
Published in International Journal of Production Research, 2019
Whereas IgG provides antigen-binding functions within the fluids and tissues of the body, IgA protects the surfaces of the mucosal epithelia that communicate with the external environment. The inverse mutation is used here because it can search a broader area.