Cells and Organs of the Immune System
Constantin A. Bona, Francisco A. Bonilla in Textbook of Immunology, 2019
Gut-associated lymphoid tissue (GALT). The tonsils (lingual, palatine and adenoidal), along with the appendix, Peyer’s patches and diffuse lymphoid tissue within the lamina propria, constitute this peripheral lymphoid organ. Tonsils are groups of large follicles underlying epithelium which invaginates irregularly to form “crypts.” The nodular structure is made up of networks of reticular cells and fibers supporting numerous primary and secondary follicles which have morphology and cellular composition identical to those in lymph nodes. Because of their location, tonsils are continually in contact with many substances and organisms, inhaled or ingested. They are an important site for initiating immune responses.
Immunological Properties of Microbial Outer Membrane Proteins and Their Effects as Modulators of LPS Immunobiology
Helmut Brade, Steven M. Opal, Stefanie N. Vogel, David C. Morrison in Endotoxin in Health and Disease, 2020
The adjuvant effect of outer membrane proteins has also been applied in attempts to produce more effective vaccines against chronic pulmonary infection with P. aeruginosa. OprF and OprI of P. aeruginosa are outer membrane proteins that are conserved in all 17 known serogroups of this microorganism (31) and represent good vaccine candidates. In a rat model, immunization with purified OprF enhanced the ability of the animals to clear a challenge inoculum of P. aeruginosa from the lungs and significantly reduced the incidence and severity of pulmonary lesions (26). However, it has been indicated that immunization with the single OprF and OprI proteins from P. aeruginosa was not as protective as immunization with LPS-based vaccines (31). On the other hand, Oprl-OprF fusion proteins seem to offer more promise (31), and improved methods of expressing the fusion proteins have been developed (32). Another approach has been to insert foreign antigenic determinants into the OprF molecule through linker insertion mutagenesis (33). Also, antigens inserted into the third or fourth loop of OmpA of E. coli and expressed in Salmonella typhimurium have been constructed. The strategy here is to deliver antigens to the gut-associated lymphoid tissue to induce secretory, humoral, and cellular responses (34).
The BB Rat: A Unique Model of Human Type I Diabetes
John H. McNeill in Experimental Models of Diabetes, 2018
The gut represents the largest immune organ in the body, and migration of immune cells to the rat gut begins during the first postnatal week and is not complete until approximately 4 weeks of age.296 This corresponds to the period when diet modulates the expression of autoimmune diabetes in the BB rat. Maturation of the gut-associated lymphoid tissue relies on the presence of antigens,296 and there is evidence that gut-associated lymphoid tissue function is affected by nutritional status.297 The gut of the young animal is permeable to macromolecules (undigested and partially digested food antigens) that can enter the circulation and induce antibody production.298 There are phenotypic and functional differences in immune cells in the neonatal as compared with the mature adult gut.299 Consistent with this hypothesis, DP-BB rats exposed to cow’s milk protein later in life are not as susceptible to its diabetogenic effects.291 In addition, early diet (less than 5 weeks postweaning) has been shown to have irreversible effects on gut size and possibly nutrient transport, providing the basis for the concept of “critical period programming.”300 Differences in the development of the intestine have been reported between DP and DR-BB rats.301
B cells and upper airway disease: allergic rhinitis and chronic rhinosinusitis with nasal polyps evaluated
Published in Expert Review of Clinical Immunology, 2021
Harsha H Kariyawasam, Louisa K James
The network of regional lymph nodes, the tonsil and Peyer’s patches of the gut support germinal center responses that induce memory B cells which are primed for homing to local tissues. These latter two SLOs form part of the MALT and are vital for inductive immunity at mucosal barriers [71] . Tonsils, the adenoids, and paired palatine and lingual tonsils are a major immune inductive site of the airway. Memory B cells produced in the tonsils generate systemic immune responses, also seeding the nasopharynx by virtue of surface expression of adhesion molecules which facilitate preferential homing to respiratory tissue [72]. In contrast, gut-associated lymphoid tissue induces immunity localized to the gastrointestinal tract. In addition to the SLO, germinal center-like responses can occur in non-lymphoid tissue, including the airways, either transiently during acute infection or in the context of dysregulated chronic inflammation [73]. Germinal centers in SLOs are highly organized with compartmentalized expression of chemokines and adhesion molecules, which regulate the movement of B cells between spatially distinct regions. Contrastingly, germinal center-like responses that occur in non-lymphoid tissue often involve loosely organized clusters of immune cells termed ectopic or isolated lymphoid follicles. The presence of ectopic lymphoid follicles in chronic inflammation is associated with immune dysregulation and may be a consequence of a failure in pathogen clearance or of autoimmune responses in damaged tissue. Such findings have significant implications for inflammatory airway mucosal disease.
Gastrointestinal manifestations of primary immune deficiencies in children
Published in International Reviews of Immunology, 2018
In their severe form, primary immune deficiencies can lead to increased susceptibility to serious infections during infancy and even death. In the less severe form, they can present later in childhood or adolescence with subtle signs and symptoms and they can often mimic other conditions. It is quite common for primary immune deficiency to mimic gastrointestinal diseases as the gastrointestinal system is the largest lymphoid organ of the human body containing T and B lymphocytes, macrophages, and dendritic cells.4,5 The lumen of the gut is heavily populated with pathogens which come into regular contact with these immune cells. The lymphoid tissue in the gut is known as gut associated lymphoid tissue (GALT), consisting of Peyers patches and mesenteric lymph nodes which provide effective innate and adaptive immune responses.4,5 The mucosal surface of the gut protects itself from invasion by micro-organisms by forming a barrier containing macrophages, lymphocytes and other immune cells (Figures 1, 2 and 3). This allows immune recognition and response against microbial antigens in the gut. Protective mechanisms include the ability to secrete antimicrobial peptides and serum immunoglobulin A. Genetic defects affecting gut epithelial barrier function, neutrophil granulation as well as T and B lymphocytes are known to predispose affected individuals to inflammatory bowel-like disease.6–9
Immunopathological and molecular basis of functional dyspepsia and current therapeutic approaches
Published in Expert Review of Clinical Immunology, 2018
Mounika Addula, Victoria E. D. Wilson, Savio Reddymasu, Devendra K. Agrawal
Recent advances have contributed to a better understanding in immuno-pathophysiology of FD. A shift in focus has been to duodenal pathology from gastric pathology. Previously, gut motility was considered the main pathophysiological pathway but now advances in immunologic and genetic studies with open possibilities for other symptomatic mechanisms. There is evidence of close interaction between innate and acquired immune response in the pathophysiology of FD. However, it would be more informative to delineate the role of individual cell and cytokine and the underlying mechanism on the inflammatory pathophysiology and clinical symptoms in FD. Detailed studies on the role of gut-associated lymphoid tissue in infectious and noninfectious mechanisms of FD are warranted. One of the promising areas for future investigation include case-controlled studies in healthy and FD subjects to examine the changes in various pro-inflammatory and anti-inflammatory cytokines, such as IL-1β, TNF-α, and IL-10, and correlate with the changes in the subtypes of gut-homing T-lymphocytes, including CD4+α4β7+CCR9+cells with delayed gastric emptying and pathophysiological features of FD. Furthermore, potential effects of neuro-immune mechanisms and the interaction with gastro-intestinal immune response may provide insights on the enteric glial pathology in FD. In this regard, detailed studies on the role of gut microbiota and their changes under various conditions, including inflammation, stress, anxiety, and allergy, could be promising in providing insight into the pathogenesis of FD.
Related Knowledge Centers
- Antibody
- Epithelium
- Gastrointestinal Tract
- Intestinal Villus
- Lymph Node
- Spleen
- Bone Marrow
- Immune System
- Plasma Cell
- Mucosa-Associated Lymphoid Tissue