Antibodies (immunoglobulins)

Which fraction of the serum proteins do the antibodies belong to?

The gamma-globulin fraction.

How are antibodies structured?

They are Y-shaped or T-shaped polypeptides, they have two identical heavy chains and two identical light chains.

What are antibodies considered as?

Complex glycoproteins.

Why are antibodies considered complex glycoproteins?

Because they are attached by a disulfied bond and conjugated with carbohydrates.

Why do antibodies have specificity for antigens?

Because the amino acid sequence in the variable regions at the tips of the "Y" varies greatly, allowing specific binding to antigens.

How many types of antibodies are there?

Five

What are the five types of antibodies?

1- IgG

2- IgM

3- IgA

4- IgD

5- IgE

What do the antibody groups differ in?

Structure and biological activity.

What is the other name of an antibody class?

An isotype

IgM is used to detect which phase of the infection?

The early phase

Which organ is the IgM unable to cross?

The placenta

IgM is secreted first during which exposure?

The primary exposure.

What is IgM used as a marker for?

A recent infection.

IgG makes up how much of the total immunoglobulins?

70-75%

IgG is secreted in high quantities during which exposures?

Secondary exposures

What does a 4-fold rise in IgG indicate?

Active infection.

A single positive sample of IgG indicates what?

Past exposure.

How does IgA exist in serum?

As a monomer (single unit).

Why is IgA dimeric in secretions of the gastrointestinal and respiratory tracts?

Because it is joined by a secretory component that forms a dimer, allowing it to function effectively in mucosal surfaces.

How does IgD exist in serum?

As a monomeric.

IgD is presented on the surface of what?

B Lymphocytes

What is a function of IgD in relation to the membrane?

It functions as a membrane receptor.

How does IgE exist in serum?

As a monomeric

IgE is associated with which medical emergency?

Anaphylaxis

IgE plays a role in immunity against which type of pathogen?

Parasites

Why is IgM considered the primary antibody in the immune response?

Because it is produced first in response to many antigens during the primary immune response.

Why do IgM levels not remain elevated for long?

Because IgM levels rise quickly but remain high only transiently before declining.

Why is IgG associated with long-term immunity?

Because it persists in small amounts throughout life after the initial immune response.

Why is IgG produced in large amounts during the secondary response?

Because memory cells formed after the primary response rapidly produce large amounts of IgG upon re-exposure to the antigen.