Lecture 18 - Immunodiagnostics Flashcards
Define:
Antigen
molecule that can bind BCR/TCR (usually associated with pathogens)
Define:
Antibody
antigen-binding (specific) protein produced by B cells
What does the “nature” of antigen diagnostic tests work with
how the binding will occur
What three binding-based tests are there
- agglutination (complex)
- precipitation (soluble)
- flocculation
What does antibody function diagnostic test work with
how the antibody neutralizes the antigen
What are the three antibody functions that respective tests look at
- neutralization
- complement fixation
- hemolysis
What immunoglobulin causes agglutination more effectively? Why?
IgM; it is a pentamer
Give an example of an agglutination test
ABO blood typingW\
What is the prozone
too many antibodies result in no agglutination
what is the post zone
less antibodies but more free-floating antigens
what are the limitations of precipitation tests
there needs to be large amounts of antibodies and antigens
T/F: in a complement fixation test, the formation of a complex means the complement protein is in use
True
a medial line is a precipitation test is considered to be ____ and having ____ amounts of antigen and antibody
positive; equal
Fixing means
complement protein is in use
what does C3b bind to
antibodies
How do fluorescent antibody techniques work
detect specific molecules/structures on or within cells
direct FAT
single fluorescent labeled antibody binding to target antigen
Indirect FAT
uses two antibodies (primary that binds target and secondary that binds to complex)
FITC appears as ____ while PE appears as ____
green; red
Flow cytometry
informs us about cell types in blood/tissue
Explain the 3 steps of flow cytometry
- single cells are hit by particular wavelength
- emitted light detected by the photomultiplier and converted to a digital pulse
- expressed as dot plot or histogram
What are the 4 types of ELISA
- direct
- indirect
- sandwich
- competitive
What is ELISA (enzyme linked immuno-sorbent assay)
a plate based test that detects and measures antibodies in a sample
Explain:
direct ELISA
primary antibody is conjugated
Explain:
indirect ELISA
primary antibody is unconjugated, need secondary
Explain:
sandwich ELISA
detecting antigen
capture antibody (unconjugated) and detection antibody (conjugated)
Explain:
competitive ELISA
used to measure concentration of Ag/Ab in sample by detecting interference
What is the interpretation of:
+ antigen, + antibody
acute infection
What is the interpretation of:
+ antigen, - antibody
early infection
What is the interpretation of:
- antigen, + antibody
previous infection
What is the interpretation of:
- antigen, - antibody
negative (no current or past infection)
