IgM is the first antibody to be produced in response to any antigen (foreign particle) invasion, while IgG is most abundantly found antibody in the human body. IgM is the largest immunoglobulin among all, with pentamer units and ten antigens binding site. IgG are responsible for humoral immunity and is a monomer unit which is lighter and smaller, with two antigen binding site. Due to the smaller size of this antibody, it is able to travel through the bloodstream.
Our Immune system is one of the most effective defense mechanism in the body. It can recognize foreign particle and protect our body by eliminating these foreign particles, which is also termed as ‘Antigens‘ against which antibody are been produced by the body.
Antigens can be a protein or a carbohydrate that evoke immune response resulting in the development of ‘Antibodies‘ also called as Immunoglobulins. These immunoglobulins are proteins produced by B- lymphocyte namely IgG, IgA, IgM, IgD, and IgE. In this article, we will discuss the difference between two immunoglobulin namely IgM and IgG.
Content: Immunoglobulin M (IgM) Vs Immunoglobulin G (IgG)
Comparison Chart
| Basis for Comparision | Immunoglobulin (Ig) M | Immunoglobulin (Ig) G |
|---|---|---|
| Molecular weight | 900,000MW or 900kDa. | 150,000MW or 150kDa. |
| Presence in serum | 10% of total serum. | 75% of total serum. |
| Percentage of Carbohydrate | 12. | 3. |
| Heavy chain | mu (µ). | gamma (γ ). |
| Light chains | kappa (κ ) and lambda ( λ). | kappa (κ ) and lambda ( λ). |
| Types | No more types. | Are of four types IgG1, IgG2, IgG3, IgG4. |
| Size | It is pentamer consisting of 5 Y-shaped units together by a polypeptide chain with ten antigen binding sites. | It is a monomer consisting of the single Y-shaped unit with only two antigen binding sites. |
| Role | IgM serves as the first kind of defense, which means it is the first antibody to be immediately developed when any foreign particle is introduced, though its function is temporary. | IgG is a long term response for any disease and thus protect our body from viral and bacterial attacks. |
| Where it is found | IgM is found in lymph fluid and blood and is produced in plasma cells. | Abundantly found in lymph, blood, and intestine. |
| Effect of high level | High level of IgM may give rise to parasitic infections, kidney damage, rheumatoid arthritis, hepatitis, mononucleosis. | High level of IgG in the body means a long-term infection like HIV, multiple sclerosis, multiple myeloma. |
| Effect of Low-level | Low level of IgM results in few types of leukaemia, and some inherited diseases. | Low level of IgG results in kidney damage and few types of infections. |
Definition of Immunoglobulin M (IgM)
All Immunoglobulins (Ig) or antibodies are proteins developed by B-lymphocytes. IgM is the largest antibody, found in blood and lymph and developed by plasma cells.
IgM is the first antibody produced in response to any antigen or foreign particle and are most effective in evading any bacteria, virus, and other pathogens. Even the amount of IgM produced at the time of exposure to antigen is six times greater than IgG. It’s the first antibody produced in the human fetus.
It’s a pentamer composed 5 Y-shaped units joint together by polypeptide chain. IgM also has ten antigen binding site with the heavy chain as mu ( μ) and light chain of kappa ( κ) and lambda (λ ). However, only five are functional antigen binding sites. As the size of IgM is larger as compared to other immunoglobulins, hence their presence is only 5- 10% of total blood serum.
The effect of IgM is temporary and they disappear, after 2-3 weeks of their production. High level of IgM may give rise to parasitic infections, kidney damage, rheumatoid arthritis, hepatitis, mononucleosis. Even if the level of IgM in the newborn is high it means the child had already caught an infection in the mother’s womb before the birth.
Low level of IgM results in few types of leukemia, myeloma, and some inherited diseases. So we can say that the presence of IgM marks certain kind of infection in the body.
Definition of Immunoglobulin G (IgG)
The presence of IgG is 75%-80% in total blood serum. It is most abundantly found in the body, produced by white blood cells. IgG is the smallest antibody among all consisting of only single Y-shaped monomer unit. It also has two antigen binding site and heavy chain of gamma (γ ) as the well light chain of kappa (κ ) and lambda ( λ).
IgG is the long-term response to any disease or infection. It is of four types IgG1, IgG2, IgG3, IgG4. Due to small size, it can travel through the blood and most importantly IgG is the only antibody that can cross the placenta and transfers mother’s immunity to the developing embryo. IgG is produced at the later stage of infection, but their effect is for a long time and helps in complete eradication of infections or diseases.
Thus IgG plays an important role in producing the secondary immune response against any antigen, promoting opsonization, phagocytosis and in fighting with viruses and bacteria.
High level of IgG in the body means a long-term infection like HIV, multiple sclerosis, multiple myeloma. Low level of IgG results in kidney damage and few types of infections.
Key Differences Between IgM and IgG
Following are the key differences between IgM and IgG:
- Though both the antibodies (IgM and IgG) are proteins, made for fighting against antigens or foreign particle, IgM provides immediate response when any antigen enters the body while IgG responds later with the permanent eradication of antigen and its effect is lasting. Also, IgG helps in developing secondary immune response against any particular antigen.
- The molecular weight of IgM is 900,000MW or 900kDa and that of IgG is 150,000MW or 150kDa.
- IgM account only 10% of the total volume of the serum and IgG occupies 75% of the total volume of the serum.
- IgM has the heavy chain as mu (µ) and IgG has the gamma (γ ), though both have the light chain as kappa (κ ) and lambda ( λ).
- IgG is of four types which are – IgG1, IgG2, IgG3, and IgG4. IgM has no such types.
- IgM is produced in plasma cells and is found in lymph fluid and blood, whereas IgG is abundantly found in the intestine, lymph, blood.
- Due to the larger size, IgM is unable to cross the placenta, though it’s the first antibody produced in the human fetus while IgG is smaller in size and can cross the placenta and provides mother’s immunity to developing the embryo.
- IgM is a pentamer unit with ten antigen binding sites, but out of it, only five are functional due to many monomers bonding among themselves results in restriction to binding sites. Whereas IgG is a monomer with two antigen binding sites.
Conclusion
Immunoglobulin (Ig) or Antibodies are the proteins produced in B-lymphocytes, to fight against any infections, there is five kind of antibodies, and all plays a vital role in fighting diseases and are very specific to these antigens, these antibodies are of different size, having light and heavy chains.
IgM is the first antibody to fight against, and attack of viruses or bacteria whereas IgG reacts later but help in the permanent eradication of antigens by enhancing phagocytosis or opsonization.
nice topic for understanding immunity for infection.