Immunity in the GIT Flashcards
what are the two groups of pattern recognition receptors
cell surface - transmembrane and intracellular receptors
fluid phase soluble molecules
each lymphocyte has a unique antigen receptor - what happens when it it triggered by an pathogen
undergoes clonal expansion
what is the estimated range of antigenic variability
10^9
how any genes in the human genome
30,000
describe the mechanism of antigen presentation
antigens internalised
broken down to peptides
associate with MHC class 2 and brought to cell surface
recognition by T helper cells which are then activated
these produce cytokines needed by B cells, T cells etc
what are the roles of these molecules B lymphocytes CD8 CD4 suppressor T lymphocytes
develop potential to secret antibodies - humeral immunity
cytotoxic T lymphocytes - cellular immunity
helper T lymphocytes - secrete growth factors which control immune reponse - help B lymphocytes and T lymph
may damp down immune response
why do we need gut immunity
major site for foreigns bodies
GIT diseases kill more than 2 mill every year
lack of effective mucosal vaccines vs pathogens
what does the gut mucosal barrier encounter
harmless antigens such as food, normal flora, pathogenic organisms which try to colonise and invade - ie this is the first line of defence
what are the two types of immune response we need in the gut
ignorance / tolerance from normal flora
protection from foreign matter
what are the innate defences of the gut immune system
commons bacterial flora
epithelial barrier
biochemical faros produced by epithelial cells
what are specific defences of the gut immune system
lymphoid tissue associated with mucosal surfaces
what are m cells in the gut and what is their role
microfold cells
found in the follicle-associated epithelium of the Peyer’s patch; have the unique ability to sample Ag from the lumen of the small intestine and deliver it via transcytosis to APC and lymphocytes located in a unique pocket-like structure on their basolateral side.
what is the approx number of bacteria in the gut and how many different species
10^14
300 - 1000
describe how gut bacteria changes with age
infants acquire gut flora swallowed from breast milk or vaginal fluid at delivery
colonic microflora is adult like after 2 years of birth but don’t fully resemble until much older
elderly harbour fewer bifidobacteria and higher levels of enter-bacteria and clostridium difficile
what is a prebiotic
non-digestible food ingredient that beneficially affects the host by selectively stimulating the growth and/or activity of one or a limited number of bacteria in the colon, and thus improves host health
describe how inulin is a prebiotic
Inulin is indigestible by the human enzymes ptyalin and amylase, which are adapted to digest starch. As a result, inulin passes through much of the digestive system intact. It is only in the colon that bacteria metabolise inulin, releasing carbon dioxide, hydrogen and/or methane
what are the benefits of gut microflora
resistance to colonisation by pathogens stimulate local immunity oral tolerance nutrition epithelial cell turnover intestinal motility
what is symbiosis in the gut
in the absence of commensals a poor immune reposes develops and oral tolerance cannot be induced
what percentage of faeces in weight does bacteria take up
60%
what is the problem with antibiotic and protection in the gut
kill many commensal bacteria which allows pathogens to colonise and proliferate such as clostridium difficile
what is eubiosis and dysbiosis
state of balance between microbial population
imbalance
what is IBD
group of disorders inflammatory bowl disease
what are the most common kind of IBD
crohns and ulcerative colitis
describe the structure and function of the epithelial barrier
prevents penetration by microorganisms
single layer thick
self renewing from stems cells in crypts of leiberkhun
