Final: Ch 15: Diagnosing Infections- Immunological Methods Flashcards
how to know the history of a patient’s contact w/microorganisms or other antigens
characteristics of antibodies such as their quantity or specificity can reveal this
Serology
Involves in vitro testing of serum
Based on the principle that antibodies have an extreme specificity for antigens
Visualization of the interaction of antigens and antibodies provides a powerful tool for detecting, identifying, and quantifying antibodies or antigens
Basic principles of serological testing using antibodies and antigens
Serological tests were developed to produce an endpoint reaction visible to the naked eye or with light microscopy
Specificity (of immune testing)
property of a test to focus only on a certain antibody or antigen, and not react with an unrelated or distantly related antigen
Sensitivity (of immune testing)
detection of even minute quantities of antibodies or antigens in a specimen; reflects the degree to which a test will detect every positive person
Agglutination (& agglutination tests)
Agglutination: antigens are whole cells or organisms such as red blood cells, bacteria, or viruses
If antigen is present visible clumps of cells form
In both reactions, one antigen is interlinked by several antibodies to form insoluble aggregates
Hemagglutination
Agglutination of red blood cells
Can be used to determine blood type
Antibody titers
Titer: concentration of antibodies in a sample
Determined by serially diluting patient serum into test tubes or wells of a microtiter plate containing equal amounts of bacterial cells
Reflection of the highest dilution of serum that still produces agglutination
The more a serum sample can be diluted and still react with antigen, the greater the concentration of antibodies and thus its titer
Used to diagnose autoimmune disorders and determine past exposure to certain diseases
Immunofluorescence Testing: Fluorescent antibodies (Fabs)
Monoclonal antibodies labeled by a fluorescent dye
Use Fabs to label cells so that they can be visualized
Immunochromatography testing
Very rapid
Antigen solution flows through a porous strip and encounters labeled antibody
Visible line produced when antigen-antibody immune complexes encounter antibody against them
Used for pregnancy testing and rapid identification of infectious agents
Immunoassays
Alternative methods that employ monoclonal antibodies and permit rapid, accurate measurement of trace antigen or antibody levels due to their enhanced sensitivity
can detect more molecules of chemicals such as hormones, metabolites, and drugs
Radioimmunoassay (RIA)
Antibodies or antigens labeled with a radioactive isotope used to pinpoint minute quantities of a corresponding antigen or antibody
Used to detect hormone levels in samples and diagnose allergies
Same idea as Fabs but rather than a fluorescent dye a radioactive one is used.
ELISA
Enzyme-linked immunosorbent assay
uses 2 antibodies
Uses an enzyme as the label
Reaction of enzyme with its substrate produces colored product
Commonly used to detect presence of antibodies in serum
Antibody sandwich ELISA
Modification of the ELISA technique
Commonly used to detect antigen
Antigen being tested for is “sandwiched” between two antibody molecules
Advantages of ELISA
Can detect either antibody or antigen
Can quantify amounts of antigen or antibody
Easy to perform and can test many samples quickly
Plates coated with antigen and gelatin can be stored for later testing
