Antibody Antigen interactions Immunology - Exam 1

What is an antigen?

Any molecule that can be bound by an antibody.

What is an epitope?

The region of an antigen that is bound or contacted by an antibody.

What is another name for an epitope?

Antigenic determinant.

Can a single antigen have multiple epitopes?

Yes. A single antigen may have many different or identical epitopes.

What types of molecules make up most biologically relevant antigens?

Proteins make up the vast majority, followed to a lesser extent by carbohydrates.

What is the difference between an antigen and an epitope?

An antigen is the molecule that can be bound by an antibody; an epitope is the specific region of that antigen that the antibody contacts.

Where on an antibody does antigen binding occur?

At the antigen-binding region involving the antibody's CDRs.

What are CDRs?

Complementarity-determining regions, also called hypervariable regions, that interact with antigens.

What type of bonds are responsible for antibody-antigen binding?

Non-covalent interactions.

Is antibody-antigen binding covalent or non-covalent?

Non-covalent.

What is a linear epitope?

An epitope formed by a continuous sequence of amino acids in the antigen's primary structure.

What is a conformationally dependent (discontinuous) epitope?

An epitope formed by regions of an antigen that come together because of the antigen's three-dimensional structure.

What is the difference between a linear and conformational epitope?

A linear epitope consists of a continuous sequence, while a conformational epitope depends on the antigen's three-dimensional structure and involves regions that may be separated in the primary sequence.

What is antibody affinity?

The strength of binding between a single Fab region of an antibody and a single epitope.

What is antibody avidity?

The collective strength of binding between multiple Fab regions of a single antibody or antibody complex and multiple epitopes.

What is the key difference between affinity and avidity?

Affinity describes one Fab binding to one epitope; avidity describes the combined strength of multiple antibody-antigen interactions.

Which involves multiple binding interactions: affinity or avidity?

Avidity.

Which describes the strength of a single Fab-epitope interaction?

Affinity.

Why can avidity be considered a collective binding strength?

Because it reflects the combined strength of multiple Fab regions binding multiple epitopes.

What is the Coggins test?

An assay used to determine a horse's prior exposure to equine infectious anemia virus (EIAV).

What method is used in the Coggins test according to the lecture?

The Ouchterlony method.

What does EIAV stand for?

Equine infectious anemia virus.

What is placed in the center well in the Coggins test described in the lecture?

EIAV antigens.

What is placed in the outer wells in the Coggins test?

Serum containing antibodies from different horses.

What is the purpose of the Coggins test?

To determine whether a horse has been previously exposed to EIAV.

What principle does the Coggins test demonstrate?

Antibody-antigen interactions.

What is a conjugated antibody?

An antibody that has another molecule attached to it so that its binding can be detected or visualized.

What types of molecules can be conjugated to antibodies?

The lecture identifies conjugated antibodies as an important tool in antibody-based assays; commonly, detectable labels such as enzymes or fluorescent molecules can be attached.

What is an ELISA?

An enzyme-linked immunosorbent assay that uses antibody-antigen interactions to detect a target.

What does ELISA stand for?

Enzyme-linked immunosorbent assay.

What is the basic principle of an ELISA?

An antibody-antigen interaction is used to detect a target, with an enzyme-linked component providing a detectable signal.

What role do antibodies play in an ELISA?

They specifically bind the antigen or antibodies being detected, depending on the type of ELISA.

What role does the antigen play in an ELISA?

It can serve as the target recognized by an antibody, depending on the assay design.

What is a Western blot?

An antibody-based assay used to detect specific proteins after they have been separated.

What role does the antibody play in a Western blot?

The antibody specifically recognizes and binds the target protein.

What role does the antigen play in a Western blot?

The antigen/target protein is what the antibody recognizes and binds.

What is a primary antibody?

The antibody that directly recognizes and binds the target antigen.

What is a secondary antibody?

An antibody that recognizes and binds the primary antibody and can be used to help detect the primary antibody in assays such as ELISA or immunohistochemistry.

What is the relationship between a primary and secondary antibody?

The primary antibody binds the target antigen, while the secondary antibody binds the primary antibody.

What is immunofluorescence used for?

Identification of intracellular or cell-surface antigens.

What can antibody-based immunofluorescence identify?

Intracellular or cell-surface antigens.