What are the differences between IgM and IgG antibodies?

Question

Accepted Answer

IgG and IgM are two of 5 types of antibodies found in the blood. Representing different stages of an immune response, IgM and IgG have several differences between them. The IgM antibody is the largest antibody found in the blood and lymph fluid, and the first to appear to fight off a new infection. IgM antibodies are the first line of immune defense against fighting pathogens.
The immunoglobulin G (IgG), on the other hand, is the most common antibody found in the blood and a major effector molecule of the humoral response that accounts for about 75 percent of serum antibodies in humans.

Basis of Differentiation

IgM

IgG

Definition

IgM antibodies are found primarily in the lymph and blood fluid and represent the first line of immune defense against invading pathogens

IgG antibodies can be found in the blood and other fluids of the body and they are formed a few days after the pathogen invasion occurs

Size

Largest of all antibodies

Smallest of all antibodies

Number of antigen-binding sites

10

2

Occurrence

Found in blood and lymph fluids

Found in all body fluids

Approximate composition

Makes up about 5-10% of all antibodies

Makes up about 75-80% of all antibodies

Time of production after pathogen invasion

IgM are produced in the early stages. They are the first antibodies to be synthesized by the body in case of a new invasion, typically produced.

IgG is produced in the later stages. They are produced a few days after the infection occurs’.

Detection

IgM antibodies can be detected about 4 -7 days after infection occurs.

IgG antibodies can be detected starting 7-14 days post-infection and are detected for weeks, months, or even years later.

Life span

IgM antibodies are short-lived. The numbers keep increasing for a few weeks after the infection occurs and then dip after the production of IgG is triggered.

IgG antibodies have a long life. They often persist for life, laying the foundation for long-term protection against pathogens.

Ability to cross placenta

IgM antibodies are unable to cross the placenta.

IgG antibodies are capable of crossing the placenta and play a key role in protecting the fetus

Subclasses

No subclasses

Four subclasses – IgG1, IgG2, IgG3, IgG4

Role

involved in cytosolic reactions and agglutination

associates with isotopes, activates the complement system

Basis of Differentiation	IgM	IgG
Definition	IgM antibodies are found primarily in the lymph and blood fluid and represent the first line of immune defense against invading pathogens	IgG antibodies can be found in the blood and other fluids of the body and they are formed a few days after the pathogen invasion occurs
Size	Largest of all antibodies	Smallest of all antibodies
Number of antigen-binding sites	10	2
Occurrence	Found in blood and lymph fluids	Found in all body fluids
Approximate composition	Makes up about 5-10% of all antibodies	Makes up about 75-80% of all antibodies
Time of production after pathogen invasion	IgM are produced in the early stages. They are the first antibodies to be synthesized by the body in case of a new invasion, typically produced.	IgG is produced in the later stages. They are produced a few days after the infection occurs’.
Detection	IgM antibodies can be detected about 4 -7 days after infection occurs.	IgG antibodies can be detected starting 7-14 days post-infection and are detected for weeks, months, or even years later.
Life span	IgM antibodies are short-lived. The numbers keep increasing for a few weeks after the infection occurs and then dip after the production of IgG is triggered.	IgG antibodies have a long life. They often persist for life, laying the foundation for long-term protection against pathogens.
Ability to cross placenta	IgM antibodies are unable to cross the placenta.	IgG antibodies are capable of crossing the placenta and play a key role in protecting the fetus
Subclasses	No subclasses	Four subclasses – IgG1, IgG2, IgG3, IgG4
Role	involved in cytosolic reactions and agglutination	associates with isotopes, activates the complement system

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