6. anitgens immunogens for posting

What is an antigen?

Any molecule that can be bound by an antibody or T cell (via MHC).

What is an epitope?

A small specific part of an antigen that is actually recognized and bound by BCR/TCR. many epitopes in 1 antigen.

How many epitopes can one antigen have?

Many; a single antigen contains multiple different epitopes. + the same epitope is often repeated on an antigen.

What are the 4 main biomolecule types of antigens?

Proteins, polysaccharides, nucleic acids, lipids.

Which type is the BEST immunogen?

Proteins.

Why are proteins highly immunogenic?

Complex structure and diverse shapes → easily recognized by immune system. more visible to an antibody.

When do polysaccharides, lipids, and nucleic acids trigger immune response?

Usually only when attached to proteins.

Why do polysaccharides have high epitope density?

Repeating subunits create many identical epitopes.

Why are non-protein antigens NOT presented to T cells?

TCRs only recognize peptides (from proteins).

Key difference: antigen vs immunogen?

All immunogens are antigens, but not all antigens are immunogens.

Can anything be an antigen?

Yes, if it can bind an antibody and/or T cell after MHC pres

What is an adjuvant?

Substance that enhances the immune response to an antigen.

Why use adjuvants?

To increase strength and duration of immune response.

Increase exposure time or improve uptake (phagocytosis).

Do adjuvants bind permanently to antigens?

No, they are mixed but not covalently linked.

When are adjuvants used?

When antigen is immunogenic but needs help boosting response.

What is a hapten? Are haptens antigenic, immunogenic, or both?

Small molecule that can bind antibodies but cannot trigger immune response alone.

Antigenic

Why are haptens not immunogenic?

Too small and chemically simple.

How can a hapten become immunogenic?

By chemically binding to a immuhogenic carrier protein.

What is haptenation in real life?

Drugs binding to cells (like RBCs) and triggering immune response.

Example of hapten-induced disease?

Drug-induced hemolytic anemia. high dose prolonged period

Common drugs causing hapten reactions?

Penicillin, methyldopa.

Do B cells and T cells recognize the same epitopes?

Usually no.

What do BCRs bind?

Native (whole) antigens outside cells floating.

What do TCRs bind?

rocessed peptide fragments presented on MHC.

Where must BCR epitopes be located?

accesible On the surface of the antigen.

What types of epitopes can BCR recognize?

Sequential (linear) or discontinuous (conformational).

What molecules can BCR recognize?

Proteins, polysaccharides, lipids, nucleic acids. no carbs

What type of epitopes do TCRs recognize?

Only sequential (linear peptides).

Why must TCR epitopes be sequential?

Antigens are processed into peptide fragments.

Do TCR epitopes need to be on the surface originally?

No, they can come from internal proteins.

What is required for TCR recognition?

Presentation on MHC molecules.

What type of molecules do TCRs recognize?

Almost always proteins.

Can the same antigen have different epitopes for BCR and TCR?

Yes.