What is the collective term for the large numbers of microorganisms that colonize the surfaces of the healthy body, especially the intestine?
Explanation
This question tests the basic terminology for the community of commensal organisms living in and on the host, a central topic of the later sections of Chapter 12.
Other questions
What is the approximate surface area of the human small intestine, making it a significant interface for the mucosal immune system?
What is a key feature of microfold cells (M cells) that makes them a preferred route for antigen entry into Peyer's patches?
In the small intestine, what is the predominant type of T cell found within the epithelium, and what type predominates in the lamina propria?
What is the primary adhesion molecule on gut endothelial cells that facilitates the gut-specific homing of lymphocytes, and which integrin on the lymphocytes binds to it?
Which chemokine, produced by epithelial cells in the small intestine, is a ligand for the CCR9 receptor on gut-homing T and B cells?
What is the dominant class of antibody produced locally by plasma cells in the mucosal immune system?
In the human gut, class switching of activated B cells to produce IgA is controlled by which cytokine?
In humans, the ratio of IgA1 to IgA2 isotypes varies by tissue. What is the approximate ratio of IgA1 to IgA2 in the small intestine?
What is the function of the polymeric immunoglobulin receptor (pIgR)?
Selective IgA deficiency is the most common primary immune deficiency in humans. How is this deficiency often compensated for, preventing most individuals from being overly susceptible to infections?
What is the approximate number of intraepithelial lymphocytes (IELs) found for every 100 epithelial cells in the healthy human small intestine?
What is a key distinction between type a ('inducible') and type b ('natural') intraepithelial T cells (IELs)?
Type b intraepithelial T cells (IELs) can recognize and kill stressed epithelial cells. Which receptor on the IELs binds to MIC-A and MIC-B on the stressed cells to mediate this process?
What is the function of retinoic acid produced by mucosal dendritic cells in the gut?
What is a key functional difference between macrophages and dendritic cells in the lamina propria of a healthy intestine?
Which of the following pathogens is specifically mentioned as targeting M cells to gain access to the subepithelial space?
The palatine tonsils, adenoids, and lingual tonsils form a structure at the back of the mouth that guards the entrance to the gut and airways. What is this ring of lymphoid tissue called?
What is the approximate ratio of CD4 to CD8 T cells in the healthy intestinal lamina propria?
Innate lymphoid cells type 3 (ILC3s) are prominent in the intestinal mucosa. In response to IL-23 from dendritic cells, what key cytokine do ILC3s produce?
The development of Innate Lymphoid Cells type 3 (ILC3s) in the intestine is controlled by the aryl hydrocarbon receptor and which key transcription factor?
The development of type b intraepithelial lymphocytes (IELs) and ILC3s is dependent on a transcription factor activated by environmental ligands from dietary vegetables. What is this receptor?
What is the term for the phenomenon where oral administration of a protein antigen renders the systemic and mucosal immune systems relatively unresponsive to that same antigen?
What condition is described as being caused by the overgrowth of the bacterium Clostridium difficile in the gut, often after treatment with broad-spectrum antibiotics?
Up to what percentage of commensal organisms living in the gut lumen appear to be coated by IgA, a mechanism that helps control the microbiota?
What is the term for the state of controlled, low-level immune activation in the intestine, driven by the need to manage the microbiota without causing damaging inflammation?
Colonization of germ-free mice with which specific type of bacteria is mentioned to enhance IgA production and the accumulation of intestinal effector TH17 T cells?
Polysaccharide A (PSA), a component of the bacterium Bacteroides fragilis, has what effect on the mucosal immune system?
What is a key difference in the development of the gut-associated lymphoid tissues (GALT) compared to the systemic lymphoid organs?
In the mouse gut, what are the small aggregates of dendritic cells and lymphoid tissue inducer (LTi) cells from which isolated lymphoid follicles seem to arise?
Recruitment of naive B cells to Peyer's patches and isolated lymphoid follicles is important for mucosal immunity. This recruitment depends on their response to CXCL13 produced in B-cell follicles via which chemokine receptor?
Dendritic cells in the Peyer's patch subepithelial dome are recruited towards the follicle-associated epithelium in response to the chemokine CCL20. Which receptor on the dendritic cells binds CCL20?
What is the function of the chemokine CCL28 (MEC) in the mucosal immune system?
What integrin is expressed by intraepithelial lymphocytes (IELs) of the small intestine that allows them to be retained in the epithelium by binding to E-cadherin?
Paneth cells, which are specialized epithelial cells in the small intestine, produce antimicrobial peptides like RegIIIγ and defensins in response to which cytokine from TH17 cells or ILC3s?
The intracellular sensors NOD1 and NOD2 detect components of bacterial cell walls. NOD2 recognizes a muramyl dipeptide found in the peptidoglycans of most bacteria, while NOD1 recognizes a peptide found only in the cell walls of which type of bacteria?
What is the term for the process in which a cell engulfs its own cytoplasmic contents into a double-membrane vesicle that then fuses with lysosomes for degradation, a mechanism important for epithelial defense against infection?
Which cytokine, produced by TH2 cells and ILC2s during parasitic infections, is described as directly stimulating epithelial cell division to create a 'moving target' for organisms trying to attach to the epithelium?
The idea of a 'common mucosal immune system,' where priming lymphocytes in one mucosal tissue can lead to immunity in another, is a crucial concept for which practical application?
The microbiota colonizes the healthy large intestine at very high densities. By what factor are these bacteria the most numerous cells in the body?
Which T helper cell subset is particularly prominent in the healthy intestinal mucosa, where its product IL-17 is needed for full expression of the poly-immunoglobulin receptor (pIgR)?
What do mucosal invariant T (MAIT) cells recognize, allowing them to contribute to immunity in the lamina propria?
In addition to their T-cell receptor, how do type b intraepithelial lymphocytes (IELs) recognize stressed epithelial cells that upregulate the expression of MIC-A and MIC-B?
According to Figure 12.16, which of the following is NOT a method by which Salmonella bacteria penetrate the epithelial layer?
What is the primary role of TGF-β produced by dendritic and epithelial cells in the healthy gut environment?
What is the estimated percentage of the mucosal dendritic cell population that emigrates to the mesenteric lymph nodes each day in the resting intestine?
What is a key difference described between IgA production in humans and mice?
Unlike macrophages in other parts of the body, what is a key characteristic of intestinal macrophages in the healthy gut?
What is the observed phenotype in knockout mice that lack the polymeric Ig receptor (pIgR)?
In the absence of infection or inflammation, what is the primary outcome of the encounter between migrating mucosal dendritic cells and naive T cells in the mesenteric lymph nodes?