trigger 4 - sepsis Flashcards
which 2 signalling pathways lead to activation of NF-KappaB
classical (canonical) pathway
alternative (non-canonical) pathway
IkB is degraded in the proteasome enabling NF-kB transcription factor to…..
… translocate to the nucleus and induce gene expression
canonical signalling pathway
ligand binds to cell surface receptor (e.g. TLR)
recruitment of adaptors (e.g. TRAF) to cytoplasmic domain of receptor
adaptors recruit IKK complex
phosphorylation and degradation of IkB inhibitor
when does non-canonical signalling pathway occur
during the development of lymphoid organs responsible for generating B and T lymphocytes
process of non-canonical signalling pathway
ligand-induced activation
NF-kB inducing kinase (NIK) phosphorylates and activates IKKa complex
IKKa complex phosphorylates p100
p52/RelB heterodimer processed and liberated
IKK complex
core element of NF-kB cascade
made of two kinases and a regulatory subunit
NEMO
IKKa
IKKB
cytokines
regulatory molecules that coordinate immune responses
mechanism of JAK/STAT signalling
- ligand binds (e.g. cytokine)
- receptor dimerisation activates JAK phosphorylation of receptor
- STAT binds to phosphorylated receptor
- JAK phosphorylates STAT
- STAT dimer forms
- STAT dimer travels to nucleus
- STAT dimer binds DNA and changes gene expression
binding sites for STAT proteins
phosphotyrosine residues on the receptor proteins
JAK
JAnus Kinase
STAT
Signal Transducer and Activator of Transcription
STAT proteins are latent transcription factors
they are always present in the cytoplasm waiting to be activated by JAK
STAT dimer is an active transcription factor
travels to nucleus and binds to specific sequences in the DNA
JAK inhibitors
drugs that inhibit the kinase activity of JAK
small molecule drugs
e.g. Ruxoltinib and Tofacitinib
what processes does JAK activation stimulate
cell proliferation
cell differentiation
cell migration
apoptosis
characteristics of cardiac muscle contractions
rapid
short duration
calcium-calmodulin complex
activates myosin light chain kinase (MLCK)
MLCK
phosphorylates myosin light chains in the presence of ATP
myosin light chains
20-kD regulatory subunits found on the myosin heads
MLC phosphorylation
leads to cross-bridge formation between the myosin heads and the actin filaments
therefore smooth muscle contraction
reduced phosphorylation of MLC
VSM relaxation
cause of reduced MLC phosphorylation
- reduced release of Calcium by the SR or reduced calcium entry into the cell
- inhibition of MLCK by increased cellular concentration of cAMP
- phosphatase-activated MLC dephosphorylation
what regulates the degree of MLC phosphorylation
G-protein-couple signal transduction pathways
nitric oxide activation of guanylyl cyclase and cGMP formation
the SR re-sequesters calcium
using ATP-dependant calcium pump
why is CSF testing used
to diagnose a disease affecting the CNS
how is a CSF sample collected
lumbar puncture or spinal tap
where is CSF formed
choroid plexus
MenB vaccine
routinely administered to babies
protects against Meningococcal group B bacteria
infections can cause meningitis and septicaemia
vaccine used is Bexsero
microorganisms causing meningitis and septicaemia
meningococcal pneumococcal haemophilus influenzae type B (Hib) group A/B streptococcal E. COli listeria salmonella tuberculosis
what ligand causes JAK/STAT signallign
cytokines e.g. IFN-y, IFN-a
growth hormone
important of commensal microorganisms
out-compete pathogenic bactera
provide vitamins
colonisation resistnace
effects of antibiotics on commensal bacteris
reduce their diversty
commensal microorganisms as cause of diesease
enogenous infection
switch role and cause disease in weak immune system
produce metabolites used by pathogens
overall effect of meningitis
inflammation of lungs and subarachinoid space and psinal cord
types of meningitis
bacterial - most severe
viral
non-infectious
recurrent/chronic
symptoms of meningitis
headache
fever
rash
sepsis
seizures
diagnosis of meningitis
CSF analysis - lumbar puncture
- looking for increased proteins, neutrophils and leukocytes
CT scan/MRI
treatment for viral meningitis
none
treatment for bacterial meningtisis
vaccines
treatment of assocaited disorders
abnormal permeabiltiy of BBB
bacteria infect meninges
systemic inflammation
mechanism of meningitis
bacteria colonise and penetrate mucosal membranes
invade CNS and multiply in subarachnoid space
release pro-inflammatory cytokines
swelling and increase in intracranial pressure
oedema
dendritic cell function
recognises and endocytoses PAMPs
antigen-presenting cell vis MHC
allows differenatiation o Th cells via cytokine release
links innate and adaptive immune system
dendritic cell structure
membrane folds allow maximum interaction with other immune cells
co-stimulation of T cells
required for full t cell activation
co-stimulatory molecules expressed by both T cell and APC
e..g CD28 binds to CD80
strucutre of eosinophils
bi-lobed nucleus
small, pink cytoplasmic granules
function of eosinophils
mechanisms associated with allergies and asthma
circulate in blood and migrate to inflammatory tissues
what do eosinophils produce
toxic cationtic proteins by degranulation
ROS
enzymes
cytokines
when/where do eosinophils develo
during haematopoiesis in bone marrow
migrate to blood
mechanism of eosinophils
chemotaxis
target recognition via Fc receptors
phagocytosis
release destructive enzyme and granules
what do neutrophils respond to
cytokines
released by mast cells and macrophages
3 ways neutrophils kill invading microorganisms
phagocytosis
production of ROS
Relase of cytotoxic granules
how does neutrophil recruitment increase inflammation
they release cytokines and chemokines
e.g. IL-8
respiratory burst
rapid release of ROS from neutrophils
killing mechanisms of NK cells
release of granules containing perforin granzyme
fas/fas ligand - death signal - induces apoptosis
TRAIL - TNF-related apoptosis inducing ligand
ADCC - antibody dependent cell-mediated cytotoxicity
release of cytokiens
missing self hypothesis
NK cells recognise cells that have dont have MHC
caspase killing pathway activated on infected cell
what do NK cells respond to
recognise and respond to MHC I on infected cells
what do monocytes differentiate into
macrophages or myeloid lineage dendritic cells
what are alarmins
endogenous molecules released during infection
often debris from dying cells
e.g. DAMPs
what are DAMPs
danger/damage associated molecular patterns
what recognises alarmins
PRRs on innate immune cells
release of alarmins from dendritic cells
active release
effect of alarmins on innate immune cell
causes release of pro-inflammatory cytokines
e.g. IFN-y, IL-6, TNF-a
uses of alarmins in diagnossis
biomarkers of inflammation
examples of alarmins
heat shock proteins
fibrinogen
own DNA
hyaluronic acid
6 types of vaccine
live attenuated toxoid subunit naked dna inactivated conjugated
live attenuated vaccines
weakened version of the microbe
long-term immunity
not good for immunocompromised patients
toxoid vaccines
iactivated bacterial toxins
no risk of infection
boosters required
subunit vaccines
fragments e.g. antigens of pathogen
reduced side effects
boosters required
takes time to identify specific antigen
naked dna vaccine
pure dna injected into patient
body makes proteins after injection
doesnt work well in humans
inactivated
pathogens grown in culture then killed by heating or exposure to chemicals
e..g formaldehyde
requires multiple doses
conjugated vaccines
the outer polysaccharide coat of bacterium
effective aganist coated antigens
no risk of infection
expensive to produce
challenges to vaccine production
antigenic variation
inadequate access - some countries are poor
high costs of vaccine development
risk safety - working with pathogens
antibiotic definition
chemical compound that targets essential growth processes against bacteria
when is a broad spectrum antibiotic useful
if you dont know the disease causing bacteria
works against many bacteria
when is a narrow spectrum antibiotic useful
works well against specific bacteria
effects of bacteriostatic antibotics
total cell count plateaus
no cell growth
no cell death
bacteriocidal effecs
cell death
no cell lysis
total cell count remains the same
viable cell count decreases
bacteriolytic
cell death and cell lysis
total cell count plummits
types of antibiotic
b-lactam tetracyclin sulfonamide quinolone macrolide aminoglycoside
immediate treatment of sepsis/septic shock
antibiotics given intravenously
role of NF-kappaB
transcription factor that acts during infection to produce different cytokines
cytokines inititate inflammation and recruit immune cells
NF-kappaB held inactive by
IkB in cytoplasm
effect of intracellular ROS on NF-kappaB
causes upregulation of NF-kappaB and IKK
what are pro-inflammatory cytokines
signalling molecules released from immune cells during infection
secreted in response to PAMPs binding to PRRS
function of pr-inflammatory cytokines
activate T cells
antibody production
make diseases worse - inflammation, fever, tissue destruction
types of pro-inflammatory cytokines
interleukins
interferons
chemokines
what secretes IL-1B
Monocytes and macrophages in injured epithelial/fibroblasts
effects of IL-1B
fever
pain
inflammation
effects of INF-y
results in complement
activates macrophages and phagocytosis
what secretes INF-y
lymphocytes
effects of IL-6
makes acute phase proteins from liver
causes fever
effects of TNF-a
activates NF-kappaB
activates macrophages
role of JAK-STAT
extracellular to intracellular signalling pathway
leads to production of transcription factors
what is a tyrosine kinase
enzyme that can transfer a phosphate group from ATP to a protein in a cell
mutations in RTKs
means they can be activated without a ligand
causes uncontrolled cell growth
what allows amplification of signals
kinase phosphorylation cascades
e.g. MAPK, PIP3
2 biomarkers of inflammation
CRP and complement pathway
ESR - erythrocyte sedimentation rate
CRP as a marker of inflammation
test blood plasma
levels rapidly increase after 2 hours - peak at 48 hours
levels increase following IL-6 secretion
normal crp < 1mg/L
what is CRP
c-reactive protein
produced by liver
found in blood plasma
what is ESR
erythrocyte sedimentation rate
how fast RBC fall through column of blood
ESR as a biomarker
slow rate of ESR suggests inflammation clumping seen if increased fibrinogen sensitive test non-specific levels of fibrinogen may remain high for several days
normal ESR
men - 3 mm/h
women 7 mm/h
what regulates smooth muscle contraction
autonomic NS (para and symp)
hormones
stretching
how is contraction transmitted from cell to cell in SM
via gap junctions
they are low resistance and allow coordinated contraction
characteristics of SM contraction
Ca2+ binds to calmodulin instead of troponin
MLCK is activated and phosphorylates light chain on myosin head
cross-bridge formation
myosin light chain is phosphorylated and binds to actin
sliding filament theory
myosin head (bound to actin) moves forward
new ATP molecules (ahead) binds to myosin head
old cross-bridge detaches
