Enzyme-linked immunosorbent assay (ELISA) - Animation

Summary

ELISA, or enzyme-linked immunosorbent assay, is a highly sensitive method for detecting specific antibodies or antigens. The Direct ELISA tests for antigen presence by adsorbing an unknown antibody to a microtiter plate, followed by the addition of a sample and an enzyme-linked antibody. If the antigen is present, it binds and retains the enzyme, and a color change indicates its presence. The Indirect ELISA involves adding antigen to the plate, then serum suspected of containing antibodies, and an enzyme-linked antibody that reacts with the constant region of antibodies. A color change after substrate addition confirms the antibody's presence, offering a reliable way to identify immune responses.

Takeaways

• 🧪 ELISA is a highly sensitive test used to detect antibodies or specific antigens.
• 🔍 The Direct ELISA is used to test for the presence of an antigen by adsorbing an unknown antibody to the well of a microtiter plate.
• 💧 After rinsing to remove excess antibody, a sample suspected of containing the antigen is added to the well.
• 🔗 An enzyme-linked antibody that can react with the antigen is added, binding to the antigen if present, and is retained in the well.
• 🎨 The addition of a colorless substrate for the enzyme leads to color development, indicating the presence of the antigen.
• 🔄 The Indirect ELISA involves adding antigen to the microtiter plate well, allowing it to attach to the walls.
• 💧 Rinsing again removes excess antigen before adding serum suspected of containing antibodies.
• 🔗 An enzyme-linked antibody that reacts with the constant region of other antibodies is added in the Indirect ELISA.
• 🎨 The addition of a colorless substrate in the Indirect ELISA, followed by color development, indicates the presence of the identified antibody.
• 🔬 Both Direct and Indirect ELISA methods rely on the specific binding of antibodies to antigens for detection.
• 📈 The development of color in ELISA tests is a visual indicator of the presence of the target antigen or antibody, making it a qualitative and semi-quantitative assay.

Q & A

What is the enzyme-linked immunosorbent assay (ELISA)?

ELISA is an extremely sensitive test used to detect antibodies or specific antigens in a sample.

What is the purpose of the direct ELISA test?

The direct ELISA test is used to detect the presence of antigens by using an unknown antibody that is adsorbed to the well of a microtiter plate.

How is the antigen detected in a direct ELISA test?

In a direct ELISA, the antigen is detected by adding a sample suspected of containing the antigen. If the antigen is present, an enzyme-linked antibody that can react with the antigen is added and binds to it, which is then retained in the well.

What role does the enzyme-linked antibody play in a direct ELISA test?

The enzyme-linked antibody in a direct ELISA test binds to the antigen if it is present, indicating its presence through the retention in the well.

What is added after the enzyme-linked antibody in a direct ELISA test?

A colorless substrate for the enzyme is added after the enzyme-linked antibody in a direct ELISA test.

How is the presence of the antigen indicated in a direct ELISA test?

The presence of the antigen is indicated by the development of color after the addition of the colorless substrate for the enzyme.

What is the indirect ELISA test used for?

The indirect ELISA test is used to detect the presence of antibodies by adding antigen to the microtiter plate well and allowing it to attach to the walls.

How does the indirect ELISA test differ from the direct ELISA test?

In the indirect ELISA test, the antigen is added to the well first, followed by the serum suspected of containing antibodies, and then an enzyme-linked antibody that reacts with the constant region of other antibodies is added.

What is the final step in identifying the presence of antibodies in an indirect ELISA test?

The final step in an indirect ELISA test is the addition of a colorless substrate, and the development of color indicates the presence of the antibody being identified.

Why is rinsing necessary in both direct and indirect ELISA tests?

Rinsing is necessary to remove excess antibody or antigen, ensuring that only specific interactions are detected and avoiding false positives.

What does the development of color signify in both direct and indirect ELISA tests?

The development of color in both direct and indirect ELISA tests signifies a positive result, indicating the presence of the antigen or antibody being tested for.