Done by: Bilal M. Marwa , Abdullah Al- Harby . From the slides of: Dr. Jad AlRab. Application of immunological tests in diagnosis. LECTURE outline. Serological Tests: types of tests where serum is used to measure the amount of antibodies present in it. Serological tests.
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Antigen – antibody reactions are performed to determine the presence of either the antigen or antibody. (serological tests ).
Either the antigen or the antibody have to be known.
e.g. with a known antigen, such as influenza virus , a test can determine whether antibody to the virus is present or not .Antigen -Antibody Reactions .
In this test the antigen is particulate (visible, big and insoluble) (e.g. bacteria and red blood cells) or an inert particle (latex beads) coated with antigen.
In this test, the antigen is in soluble form (solution).
Antibody cross -links antigen molecules to form aggregates (precipitates) in the zone of equivalence: optimal proportion of antigen and antibody.
Precipitation test can be performed in solution or in semi- solid medium (agar).Precipitation test :
For antibody-antigen reaction to form a precipitate that we can see, the amount of antigen and antibody should be the same (optimum concentration).
This happens in the zone of equivalnce.
In this test, we want to measure the amount of antibodies in a serum sample.
3 mg antibody
1 mg antibody
The solution contains
1 mg antigen
Here, we have a plate with 2 holes. We add the antigen in one of them, and the serum in the other, and we allow them to diffuse and form precipitation lines at the points of optimal concentrations.
This method is used to determine whether antigens are related, identical or non –identical.
(see the next slides)4. Double immunodiffusion.
Labeled anti-IgE helps us to measure the amount of reaction
This method is used for measuring either antigen or antibody in patient serum.
(see next slide)6. Enzyme Linked Immunosorbent Assay (ELISA)
Enzyme Labelled antibody
Enzyme activity is measured by adding the substrate for the enzyme that leads to development of a color.
Intensity of color correspond to concentration of antibody.
Fluorescent dyes e.g. fluorescein and rhodamine can be covalently attached to antibody molecules and made visible by ultraviolet (UV) light in a fluorescent microscope.
Antigen fixed on slide e.g.
nuclear antigen .
An indicator system consisting of “sensitized” red blood cells (red blood cells plus anti-red blood cell antibody) is added.