What is the Difference Between IgM and IgG?

IgM and IgG are two types of antibodies produced by the immune system in response to infections. They differ in several aspects:

1. Timing: IgM antibodies are produced within a week of infection and are detectable for a short period of time, while IgG antibodies are usually produced approximately two weeks after an infection and may be detectable for months to years after an infection.
2. Location: IgM antibodies are mainly found in blood and lymph fluid, while IgG antibodies are present in blood and other body fluids.
3. Function: IgM antibodies are involved in cytosolic reactions and agglutination, while IgG antibodies associate with isotopes, activate the complement system, and provide long-term protection against microorganisms.
4. Subclasses: IgG antibodies have four subclasses (IgG1, IgG2, IgG3, IgG4), while IgM antibodies do not have subclasses.
5. Antigen-binding sites: IgM antibodies have 10 antigen-binding sites, while IgG antibodies have 2 antigen-binding sites.

In summary, IgM antibodies are produced earlier in the course of an infection and are detectable for a shorter period, while IgG antibodies are produced later and provide long-term protection. Both types of antibodies play crucial roles in the immune response to infections.

Comparative Table: IgM vs IgG

Here is a table comparing the differences between IgM and IgG antibodies:

IgM antibodies are the first type of antibody produced in the body as a response to a new infection, providing short-term protection. They are large and have 10 antigen binding sites, but only 5 of them are available for antigen binding due to conformational constraints. IgM is mainly found in blood and lymph fluids.

On the other hand, IgG antibodies are produced later in the infection and provide long-term protection. They have only 2 antigen binding sites and are found in blood, lymph, and other tissues. IgG antibodies can cross the placenta, providing passive immunity to the fetus.