What is the Difference Between IgG IgM IgA IgE and IgD?

05/20/2025 • Giovanni Medeiros

There are five classes of immunoglobulins (Ig), also known as antibodies, found in serum: IgG, IgM, IgA, IgE, and IgD. They are distinguished by the type of heavy chain they contain and have different functions in the immune system. Here are the main differences between them:

  1. IgG (gamma heavy chain):
  • Main antibody in blood
  • Powerful ability to bind to bacteria and toxins
  • Only isotype that can pass through the placenta, providing protection for newborns
  • Comprises about 70-75% of the total immunoglobulins in blood
  1. IgM (mu heavy chain):
  • Exists as a pentamer (five units of basic Y-shaped structures)
  • First immunoglobulin made by B cells as they mature
  • Mainly distributed to the lymphatic system
  • Present on the surface of B cells as the antigen receptor
  1. IgA (alpha heavy chain):
  • Mainly found in body secretions, such as tears, saliva, respiratory and intestinal secretions, and breast milk
  • Exists as monomers in blood but forms dimers in secretions
  • Provides protection against infection in mucosal areas of the body
  • Comprises about 10-15% of the total immunoglobulins in blood
  • Has two subclasses: IgA1 and IgA2
  1. IgD (delta heavy chain):
  • Present on the surface of most B cells early in their development
  • Little IgD is released into circulation
  • Role in the immune system is not completely understood
  1. IgE (epsilon heavy chain):
  • Associated with allergies, allergic diseases, and parasitic infections
  • Binds to mast cells and is involved in allergic reactions
  • Comprises about 0.5% of the total immunoglobulins in blood

These immunoglobulins play crucial roles in the immune system, protecting the body from various pathogens and allergens.

Comparative Table: IgG IgM IgA IgE vs IgD

Here is a table comparing the differences between IgG, IgM, IgA, IgE, and IgD:

Immunoglobulin Structure Function Main Location Subclasses
IgG (Immunoglobulin G) γ-chains Main antibody in blood, powerful ability to bind to bacteria and toxins, protects newborns through placenta Blood (highest concentration) IgG1, IgG2, IgG3, IgG4
IgM (Immunoglobulin M) μ-chains Mainly produced upon pathogen invasion by B cells, plays a key role in the initial immune system defense Blood (lower concentration than IgG) -
IgA (Immunoglobulin A) α-chains Found in many body secretions (tears, saliva, respiratory and intestinal secretions, breast milk), protects mucous membranes and gastrointestinal tract of newborns Secretions (tears, saliva, etc.), breast milk IgA1, IgA2
IgD (Immunoglobulin D) δ-chains Present on the surface of B cells, functions unclear but may play a role in determining whether antigens are recognized B cell surface -
IgE (Immunoglobulin E) ε-chains Believed to be involved in allergies, binds to mast cells, protects against parasitic worms Mast cells, involved in allergy -

Please note that this table summarizes the main differences between the immunoglobulins, as more complex information can be found in the sources provided.

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