Garlanda 3 Flashcards
precipitation tests results are understood by
- used formation of immune complexes (antigen-antibody)
- measures level of antigen/antibody by degree of visible precipitation of immune complexes in a gel/solution
when do we most often use precipitation tests
suspected fungal infection or pyogenic meningitis (note that that a positive result needs a large amount of antibody or antigen, bc sensitivity is low so a large amount of antigen/antibody is needed for a pos result)
what is immunodiffusion?
What 3 zones are present on the petri dish?
A type of precipitation test that measures the amount of antibody antigen complexes formed when diffused through a gel/medium in a petri dish
- has 3 zones: zone of antigen excess, zone of optimal precipitation, zone of antibody excess
turbidimetric test
measures light passing through a solution
nephelometry test
measures light reflected from a solution
agglutination tests
use the cross linking of antibodies with particulate antigens
agglutination definition
clumping of insoluble particles
precipitation definition
clumping of soluble molecules
Note that antibodies can bind to 2 or more antigens
neutralisation tests
a mixture of virus and serum is added to cell culture, the absence of cytopathic effect indicates presence of antibodies against the virus in the serum
viral hemagglutination inhibition test
is for viruses that are not cytopathic. Used for influenza, measles, and mumps
complement fixation test
is based on generation of MAC during complement activation (antibodies need complement to bind). They are used to detect the presence of specific antibodies. Not used much; maybe for coccidiodomycosis
ELISA
- antigen is attached to well in plate
- protein like gelatin is added to block the uncoated surface
- pt serum is added, and they bind
- enyzme linked anti-abs is added
- enzymes substrate is added, and the reaction produces a visible color change
ELISA is for which viruses
HIV, HEPA, HEPB
western blot has good sensitive but is highly specific
so it is used to confirm a positive result obtained with a screening test
How do you get the measurement of titre
the reciprocal of the most diluted solution yielding agglutination
What is line immunoassay
A modification of the Western blot;
its where antigens are absorbed into a nylon strip
What is RIBA immunoblot
A modification of the Western blot;
it uses synthetic/recombinant antigens
T/F immunochromatographic assays can rapidly screen specimens for specific microbial antigens or pt antibodies
T
Note that this is a modification of a western blot
Point of care testing includes which tests
- Immunofiltration assay: Rapid elisa where antigens are bound to membrane filters not plates
- Immunochromatographic assays: Antigen solution flows through a porous strip and encounters
labeled antibody
– Visible line produced when antigen-antibody immune complexes
encounter antibody against them
– Used in pregnancy testing and for rapid identification of some
infections: group A Streptococcus, Respiratory Syncytial Virus
(RSV), influenza viruses.
Define serology
the determination of the presence of specific antigens or antibodies in blood serum
antigen antibody complexes are also called
Immune complexes
types of serological tests
- Precipitation tests (immunodiffusion)
- Agglutination tests (latex agglutination)
- Neutralisation tests (virus neutralisation with cytopathic effect; viral hemagglutination inhibition test)
- Complement fixation test (for antibodies)
- Labeled antibody test (ELISA; ab-sandwich ELISA; Immunoblots, Western blot)
T/F precipitation will occur no matter the ratio of antigen to antibody present
false, too much antibody or too little will result in suboptimal percipitates
both turbidimetry and nephelometry measure?
cloudiness of a solution; They can be used to quantify the amounts of proteins in serum
Explain agglutination test
a particle (latex bead/bacterium) is coupled to a reagent antigen or abs. The resulting complex is mixed with pt specimen. If the target ab or antigen is present then it cross links the particles and produces measurable agglutination VISIBLE CLUMPS ARE FORMED
T/F complement fixation tests are more sensitive than agglutination tests
T
Adv of ELSIA
- can detect either antigen or ab
- sensitive
- can quantify amounts of antigen or antibody
- easy, quick
- inexpensive, automatic ish
- plates coated with antigen can be stored and used later
What markers assess inflammation
ESR
CRP
Procalcitonin
Fibrinogen, haptoglobin, APR
ESR depends on
- pro sedimentation factors (fibrinogen, alpha, beta, gammaglobulins)
- negative charge of RBC’s (aka zeta potential)
rouleux are
stacks of RBC that settle faster in ESR
When is ESR increased
inflammation
pregnancy
anemia
autoimmune disorders (such as rheumatoid arthritis and lupus)
infections
some kidney diseases
some cancers (such as lymphoma and multiple myeloma).
ESR: polycythemia hyperviscosity sickle cell anemia leukemia low plasma protein (due to liver or kidney disease) congestive heart failure.
decreased
C-reactive protein was the first pattern recognition receptor (PRR) to be identified.
It was named because it reacts with the C polysaccharide of Streptococcus
pneumoniae,
Its binds to lysophosphatidylcholine
expressed on the surface of dead or dying
cells (and some types of bacteria) and
activates the complement system via C1q,
promoting phagocytosis by macrophages,
which clears necrotic and apoptotic cells
and bacteria.
T/F CRP Plasma levels begin increasing within 4-6 hours
following an acute inflammatory stimulus and
the half-life of CRP is 5-7 hours, therefore the level
of CRP in the blood is regulated solely by its own
synthesis.
• In healthy adults, CRP concentrations varies
between 0.8 mg/L to 3.0 mg/L.
• CRP levels can rise to more than 500 mg/L
and peak at 48 hours.
T
CRP production increases with rheumatic and
other inflammatory diseases, infection, trauma,
necrosis, malignancy, and allergic reaction.
CRP levels:
-metabolic inflammation (e.g. atherosclerosis and
Type II diabetes mellitus): 2 to 10 mg/L
-mild inflammation and viral infections:10–40 mg/L
-active inflammation, bacterial infection: 40–200
mg/L
-severe bacterial infections and burns: >200 mg/L.
Once inflammation subsides, CRP level falls
quickly because of its short half-life (4 to 7 hours)
Procalcitonin
Peptide precursor of calcitonin. Generated by cleavage
of preprocalcitonin by endopeptidase.
116 amino acids, produced by parafollicular cells (C cells) of the thyroid and by
the neuroendocrine cells of the lung and the intestine.
Normal is (0.01 µg/L), rises
in a response to a
proinflammatory
stimulus, especially of
bacterial origin: acute
phase reactant,
Bacterial infections induce a universal
increase in the CALC-1 gene expression.
CALC-1 is not significantly induced by viral or
non-infectious inflammations.
In severe infections, blood levels of procalcitonin
may rise form 0.01 µg/L to 100 µg/L.
In serum, procalcitonin has a half-life of 25 to
30 hours.
The FDA first cleared the procalcitonin test to help
guide treatment for lower respiratory infections, such
as acute bronchitis, pneumonia, and acute forms of
chronic obstructive pulmonary disease (COPD). The
major causes of these infections are viruses rather than
bacteria, and treatment with antibiotics is not effective.
This can help reduce the unnecessary use of antibiotics.
