Antibody structure Immunology - Exam 1

What are immunoglobulins?

Proteins expressed only by B lymphocytes that serve as antigen receptors for these cells.

What is the difference between an immunoglobulin and an antibody?

Immunoglobulin refers to the membrane-bound form of the protein complex, while antibody refers to the secreted form.

Which cells express immunoglobulins?

B lymphocytes.

What is the function of membrane-bound immunoglobulin on B cells?

It serves as the antigen receptor for B cells.

What does it mean that each B cell expresses a unique immunoglobulin?

Each B cell expresses a unique immunoglobulin on its surface that binds to something different.

What does antigen-specific mean?

It means that an antibody or B-cell receptor binds specifically to a particular antigen or antigenic target.

Why is the antigen specificity of each B cell unique?

Each B cell produced in the bone marrow expresses a unique immunoglobulin on its surface that binds to something unique.

What are the two types of chains that make up an antibody?

Heavy chains and light chains.

What are the two types of light chains?

Kappa and lambda.

What are the two major types of immunoglobulin domains?

Variable domains and constant domains.

What does VH stand for?

Variable region/domain of the heavy chain.

What does VL stand for?

Variable region/domain of the light chain.

What does CH stand for?

Constant region/domain of the heavy chain.

What does CL stand for?

Constant region/domain of the light chain.

What are hypervariable regions?

Regions of an antibody that interact with and bind antigens.

What is another name for hypervariable regions?

Complementarity-determining regions (CDRs), also called hypervariable loops.

What does CDR stand for?

Complementarity-determining region.

What is the function of the CDRs?

They interact with and bind antigens.

Are the CDR regions of different antibodies identical?

No. The CDR regions of each antibody are unique.

What is the antigen-binding region of an antibody?

The region containing the variable/hypervariable regions that interacts with the antigen.

What is the Fc region?

The constant portion of the antibody complex associated with its biological/immune functions.

What is the hinge region of an antibody?

A structural region of the antibody complex identified as part of its general structure.

What are Fab and Fc fragments?

Fragments of antibodies with distinct structures and biological properties that can be produced by enzymatic digestion.

How are Fab and Fc fragments produced?

By enzymatic digestion of antibodies.

What determines the isotype (class) of an antibody?

The constant region of the heavy chain (CH region).

What are antibody isotypes?

The different classes of antibodies determined by the constant region of the heavy chain.

What is the key structural difference between antibody isotypes?

Their constant heavy-chain regions contain unique amino acid sequences and are different proteins.

What are antibody subclasses?

Subdivisions within certain antibody classes/isotypes, such as IgG subclasses and IgA1/IgA2.

What are the human IgA subclasses?

IgA1 and IgA2.

What are the mouse IgG subclasses listed in the lecture?

IgG1, IgG2a, IgG2b, IgG2c, and IgG3.

Do different antibody isotypes have the same functions?

No. Different isotypes possess different functional properties and immune functions.

What are the two types of antibody light chains?

Kappa and lambda.

Are kappa and lambda light chains functionally different?

No. The lecture states that there are no functional differences between kappa and lambda light chains.

Are kappa and lambda light chains encoded by the same gene?

No. They are encoded by separate genes.

Does an individual B cell express both kappa and lambda light chains?

No. Each individual B cell expresses only a single light-chain gene, either kappa or lambda.

What percentage of human light chains are kappa versus lambda according to the lecture?

Humans: approximately 60% kappa and 40% lambda.

What percentage of mouse light chains are kappa versus lambda according to the lecture?

Mice: approximately 95% kappa and 5% lambda.

What form of IgA is found circulating in the blood?

Monomeric IgA.

What form of IgA is secreted onto mucosal surfaces?

Dimeric IgA, called secretory IgA (sIgA).

What is secretory IgA (sIgA)?

The dimeric form of IgA secreted onto mucosal surfaces such as the lungs and intestinal lumen.

Where is secretory IgA found?

On mucosal surfaces such as the lungs and intestinal lumen.

What forms can IgM exist in?

IgM can exist as a monomeric membrane-bound form or as a pentameric secreted form.

What is the secreted form of IgM?

Pentameric IgM.

What is the membrane-bound form of IgM?

Monomeric IgM.

What is the key structural difference between secreted IgA and secreted IgM?

Secreted IgA is dimeric, whereas secreted IgM is pentameric.

Why are antibody isotypes important?

Different isotypes have unique properties, immune functions, and biological activities.