B4.072 - Strep Pneumo Capsular Model Flashcards
when dealing with a super antigen do you get a memory effect
no. T cells activated without priming
what can a capsule induce
antibody response in adults
what does a capsule prevent
opsonization and phagocytosis are reduced and thus phagocytosis is inhibited
what type of response is absent to capsules
T cell
antibodies to capsules
IgM and IgG2 and are short lived
describe IgM
high avidity low affinity and not
good at activating complement
IgM is poor at what
opsonizing
describe IgG2
main type produced in response to carbohydrates
CAN activate complement but cant bind to IgG Fc receptor so poor at opsonization
why is it not that great to produce IgG2 in response to capsular antigen
bc its not great at opsonization
what is in the capsule of GAS and why does that matter
hyaluronic acid
weakly immunogenic bc of similarity to hyaluronic acid in connective tissue
how does GAS cause strep throat
hyaluronic acid in capsule of GAS helps it attach to CD44 receptor in pharynx bc it is a hyaluronic acid receptor
describe the molecular mimicry in type B neisseria meningitidis
capsule contains sialic acid residues, similar to those in human cells, this inhibits both Ab production and alternative complement pathway
what is slime
carbohydrate coats around bacteria can be less well defined, this is called slime. Slime is often viscous and sticky which allows bacteria to attach to surfaces like catheters and teeth but also to glide
what is glycocalyx
capsules and slime can be generically called glycocalyx. Not all glycocalyces are composed of carbs
what bacteria is an example of a capsule not made of carbs
bacillus anthracis, has a capsule made of poly D glutamic acid
how can strep pneumo acquire another serotype from another bacterium?
transformation - bacteria can take up DNA from the environment
what other bacteria can transform
E. coli
what is conjugation
when two bacteria get together and transfer DNA
what is transduction
ability to transfer defined foreign sequences via vector
what are bacteria that can naturally carry out transformation
competent
is strep pneumo competent
yes naturally, no induction needed
how can e coli be induced to become competent
shock, new media
do all strep pneumoniaes have a capsule
no, just pathogenic ones
what is dessication
ability to survive harsher environments, capsule helps with this
difficulties in producing antibodies to a bacterial capsule inhibit what immune functions
T cell response
antibody opsonization
activation of C’ by classical pathway
physically protects bacterium
to T cells respond to carbohydrates
no, bc they wouldnt necessarily recognize them as foreign bc MHC doesn’t present them. MHC only presents amino acid sequences.
do antibodies respond to carbohydrate
yes
major encapsulated pathogens
Some Killers Have Pretty Nice Capsules S - strep pneumo K - klebsiella H - H. influenzae b P - pseudomonas N - niesseria meningitidis C - cryptococcus neoformans (yeast)
if capsule is so protective for bacteria how come we arent all dead from pneumonia
adaptive immunity
when you are exposed more than likely its when ur a kid and its an ear infection. When the bacteria die they shed their capsule. This exposes their protein contents (conj carbs) producing an immune response
why do older people get sicker with strep pneumo more than young ppl
impaired immunity
esp past 80
immunizing old people is hard bc of this
greater propensity to make IgG2 which doesnt opsonize well
how is pneumococci spread
aerosols. harbored in nasopharynx
most serious development of pneumocci infection
meningitis
what is phosphorycholine
on the surface of pneumococcus
by mimicking PAF binds to the host cell PAFr leading to the uptake of bacteria into a vesicle and transmigration across the epithelial or endothelial barrier
how do vaccines to capsules work
they are attached to another immunogenic molecule like diptheria toxoid
what does the diptheria vaccine contain
toxoid, NOT the bug itself bc if it doesnt have the toxin who tf cares
polysaccharides from the encapsulated bacteria that cause disease in early childhood cause what
stimulate B cells by cross linking the B cell receptor and drive the production of Igs but no production of new memory B cells such that subsequent immune responses are decreased
why does conjugating polysaccharides with other toxoids cause an immune response
the carrier protein polysaccharide conjugate vaccineis processed by the polysaccharide specific B cell and peptides are presented to carrier peptide specific T cells resulting in T cell help for the production of both plasma cells and memory B cells
with T cell help what IgGs are made
IgG1 and IgG3
good at opsonization, can activate complement and have high affinity
there are cojugated vaccines for what organism
strep pneumo
neisseria
haemophilus influenzae a and b
influenza
why is kids having an ear ache caused by strep pneumo protective long term for creating an immune response against the capsule?
bc the breakdown of dead cells causes a combo of protein (antigen/toxoid) and capsule polysaccharide essentially creating a conjugated vaccine
strep pneumo is a major cause of pneumonia in what population
alcoholics and HIV
HIV is a T cell issue, why would AIDS pts have issues with strep?
Bc you dont have T cells to present to stimulate class switching it IgG1 and IgG3
what virus is also a risk factor for strep pneumo infection
influenza
describe strep pneumo
gram + cocci that grow in chains in liquids but in pairs they are alpha hemolytic catalase negative \+ quellung test soluble in bile salts Optochin susceptible
what is ethylhydrocupereine dihydrocholirde
optochin
pathyphys of strep pneumo and how do viruses affect it
invasive disease may occur upon acquisition of a new epithelium serotype
viral infections increase pneumococcal attachment to the receptors on activated respiratory epithelium
what is pneumolysin
strep pneumo produces pneumolysin which is toxic to mammalian cell membranes by inducing pores. Can induce lysis in neutrophils
what causes symptoms of strep pneumo infection
largely due to an inflammatory response that may
cause pain by increasing pressure (otitis media), interfere with vital bodily functions, such as oxygenation of blood (pneumo)
interfere with cerebral function (meningitis)
distinctive signs and symptoms of pneumococcal pneumonia
cough and sputum production (rust colored) fever radiographic detection of an infection WBC >12,000 neutrophil leukocytosis \+ blood culture
what causes rust colored sputum in strep pneumo
breakdown of blood vessels
what causes fever in strep pneumo
breakdown of cells releasing acute phase reactants IL-1, IL-6, TNF inducing fever
what plays a role in immunity to strep pneumo
phagocytosis by neutrophils (macrophages)
opsonization by antibody or C’ is crucial
innate immunity components with strep pneumo
TLR 2 major receptor on cell surface of macrophages that recognizes it first
what is teichoic acid
part of what activates the alternative C’ pathway in strep pneumo
what components of strep pneumo cause an immune response
teichoic acid, peptidoglycan, C substance in cell wall - alternative C’
IgA - IgA1 protease
CRP can activate the classical C’
all recruit neutrophils
which cytokines play a major role in strep pneumo immunity
IL-23 stimulates IL-17, IL-31, IL-22
strep pneumo produces a protease to breakdown IgA1, why does this matter
IgA1 is the predominant form found in the blood
IgA1 is usually produced in response to what
carbohydrates, hence why capsule of strep stimulates this response
recent studies indicate TLR-8 produced by dendritic cells can play a role in the innate immunity to strep pnuemo. How?
recognizing unmethylated CpG found in bacteria and viruses
TLR 9 is intracellular
which acute phase cytokine will mainly be responsible for differetiation of Th17 cells
IL-6 - IL-23 does too but is not an acute phase reactant
complement can be activated against strep pneumo. what i the role of C’ protection against it?
recruitment of neutrophils and opsonization
what are resistant to MAC
gram + orgs
