1. Immunological Tests A harmful agent can be detected
Toxins, viruses, hard to culture bacteria
Takes advantage of the specific nature of antibodies
Rise in amount of antibody is an indicator
An increase in specific antibody is an indicator of exposure, can confirm a diagnosis.
Antibodies bind, precipitate, and agglutinate.

2. Precipitation tests
When sufficient antigen and antibody molecules interact, they precipitate out of solution
Too few antigen molecules, little ppt.
Too many, agn-aby cross links not made.
Examples
immunodiffusion: antibody and antigen react in agar to make ppt band or ring.
Immunoelectrophoresis: complex mixture of antigens separated, then reacted with antibody.

3. Immunoelectrophoresis

4. Agglutination Measuring about of antibody in patient’s serum
Dilute serum serially (usually 1:2)
Mix with known antigen. Clumping will be visible if antibody is present. When antibody is too dilute, clumping no longer seen.
The amount of dilution to produce a negative test:
Titer.
Blood typing: yes/no example of agglutination
classes.midlandstech.com/.../chap18/lecture3.htm

5. Agglutination-2 Identifying pathogens
Known antibody against the pathogen is attached to latex beads.
Mixing latex with bacterium produces clumping
Commonly used for quick tests to identify staph, strep, many others.

6. Fluorescent antibody tests
Specific antibody attached
to fluorescent dye.
antibody binds to antigens,
Use of fluorescent scope
reveals positive cells.
Very valuable tool in specific identification of pathogenic microbes of all kinds. This is DFA (direct fluor. Aby.).
In IFA, a fluorescent antibody against another antibody is used.

7. Enzyme linked immuno sorbent assay

8. ELISA-2 This technique can be used to detect antibody or antigen.
Attach antigen to the plastic
Add serum from patient; antibodies attach.
Antibodies detected with an enzyme-linked antibody against human antibodies.
Attach known antibody to plastic
antigen added, binds to antibody.
Second, enzyme-linked antibody binds to antigen.