Sero-Reactions and Neutralization (2)

Antibody rather than antigen is attached to a carrier particle

What is the principle of the reverse passive agglutination test?

Microbial antigens

What does reverse passive agglutination detect?

Staphylococcus aureus

Give one organism detected by reverse passive agglutination.

Neisseria meningitidis

Name another organism detected using reverse passive agglutination.

Viruses bind to erythrocytes causing them to clump together

What happens in viral hemagglutination tests?

Erythrocytes (red blood cells)

What type of cells are involved in viral hemagglutination?

Adenovirus III

Give one example of a virus detected by hemagglutination.

Direct and indirect agglutination tests

What are the two types of Coombs test?

To identify autoimmune hemolysis of red blood cells

What is the main purpose of the Coombs test?

Anti-Rh antibody

What antibody is detected using the Coombs test?

Autoimmune hemolytic anemia

What condition can be diagnosed using the Coombs test?

Presence of antigen inhibits agglutination

What is the principle of agglutination inhibition tests?

Pregnancy testing

What is a classic example of agglutination inhibition test?

Human chorionic gonadotropin (hCG)

What hormone is detected in pregnancy testing?

Heterophile agglutination test

What type of test is the Weil-Felix test?

Rickettsial infection

What does the Weil-Felix test detect?

Proteus vulgaris strains OX-19 and OX-2

What organisms are used in the Weil-Felix test?

Antibodies are bound to latex beads to increase antigen-binding sites

What is the principle of latex agglutination?

Visible cross-linked aggregates form

What happens when antigen is present in latex agglutination?

Soluble antigen combines with soluble antibody to form insoluble complexes

What is the principle of precipitation reactions?

Rapid invisible formation followed by slowly forming visible lattice

What are the two steps in precipitation reactions?

Antibody excess

What is the prozone in a precipitation curve?

Optimal antigen and antibody concentration

What is the zone of equivalence?

Antigen diffuses into agar with antibody forming a precipitation ring

What happens in radial immunodiffusion?

Fusion of lines forming an arc

What indicates identity in double immunodiffusion?

Fusion of two lines with a spur

What indicates partial identity in diffusion patterns?

Layering antigen over antiserum producing a precipitate at the junction

What is the principle of the ring test?

At the junction of antigen and antiserum

Where does the precipitate form in the ring test?

Ascoli’s thermoprecipitin test

Give one example of a ring test.

Grouping of streptococci by Lancefield test

What is another application of the ring test?

Serum sample is electrophoresed through an agar medium

What is the first step in immunoelectrophoresis (IEP)?

Antibody

What is placed in the trough in IEP?

Precipitin arc

What forms in immunoelectrophoresis after diffusion?

Because antigen diffuses radially and antibody diffuses from the trough

Why do antigen and antibody meet in optimal proportions in IEP?

Antigen and antibody migrate toward each other during electrophoresis

What happens in counter immunoelectrophoresis?

When antigen and antibody have opposite charges

When is counter immunoelectrophoresis applicable?

Speed

What is the major advantage of counter immunoelectrophoresis?

Qualitative

Is counter immunoelectrophoresis qualitative or quantitative?

Antigen migrates into antibody-containing gel forming a rocket-shaped precipitate

What is the principle of rocket immunoelectrophoresis?

Antigen concentration

What does the height of the rocket indicate?

No reaction

What is the expected result of a positive control in neutralization tests?

Reaction

What is the expected result of a negative control in neutralization tests?

Neutralizes infectivity of microorganisms

What does a neutralizing antibody do?

Destruction of cells by viral infection

What is cytopathic effect?

Absence of cytopathic effect

What indicates presence of antibodies in viral neutralization test?

An antibody that neutralizes a bacterial exotoxin

What is an antitoxin?

Agglutination of colloidal particles

What is flocculation?

Antigen and antiserum are mixed on a slide forming floccules

What happens in slide flocculation test?

The amount of toxin or toxoid that reacts with a fixed quantity of antitoxin (1 Lf dose)

What is measured in tube flocculation test?

Complement is fixed after antigen-antibody binding and indicates presence of specific antigen or antibody

What is the principle of complement fixation test?