Page 161 - MNU microbiology theoritical 2025

General Microbiology & Immunology (PM 401) Second level Semester 4 2024/2025

4. Radioimmunoassay (RIA

• Radioimmunoassay (RIA) are assays which are

based on the measurement of radioactivity

associated with immune complexes.

• In any particular test, the label may be on either

the antigen or the antibody.

5. Enzyme Linked Immunosorbent Assay (ELISA)

• ELISAs are a type of immunoassay that are commonly used to quantify levels

of a specific target within a sample.

• ELISAs are usually run in 96-well microplates

• The method depends on conjugation of an enzyme to either Ag or Ab, then

substrate is added as a quantitative measure of enzyme activity.

• The four main types of ELISAs

Direct | Indirect | Sandwich | Competitive

Direct ELISA

• An antigen or sample is immobilized directly on the plate

• A conjugated detection antibody binds to the target protein.

• Substrate is then added, producing a signal that is proportional to the amount of

analyte in the sample

Advantages: Fast and simple protocol

Disadvantages: Less specific since you are only using 1 antibody.

General Microbiology & Immunology (PM 401) theoretical handbook Page 150