IgG (Immunoglobulin G) and IgM (Immunoglobulin M) are types of antibodies produced by the immune system. IgG is the most abundant antibody, providing long-term immunity against pathogens, while IgM is the first antibody produced in response to an infection, providing initial defines. Both play crucial roles in the body’s immune response to protect against diseases. This article on Difference between IgG and IgM explores the similarities and differences between these two classes of antibodies.
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Difference between IgG and IgM
Learn more: Immunoglobulins: Structure and Functions
Characteristic IgG Antibodies IgM Antibodies
Structure Monomer Pentamer
Number of Antigen Binding Sites 2 (one for each monomer) 10 (2 binding sites per monomer)
Size Smaller, about 150 kDa Larger, about 900 kDa
Half-Life Longer half-life (weeks to months) Shorter half-life (days)
Timing of Production Produced during secondary immune responses Produced during primary immune responses
Maternal Transfer Crosses the placenta, conferring passive immunity to the foetus Does not cross the placenta
Tissue Distribution Found in extracellular fluids and tissues Predominantly in blood circulation
Effector Functions Opsonization, complement activation, neutralization, antibody-dependent cellular cytotoxicity (ADCC), and neonatal immunity Complement activation and agglutination of microbes
Role in Immune Response Provides long-term immunity and memory to subsequent infections Early responder to infections, signals ongoing immune response
Presence in Early Immune Response Produced later in the immune response Produced early in the immune response
Maturation of Affinity Undergoes affinity maturation in secondary immune responses Affinity maturation less prominent
Immunoglobulin Type Most abundant immunoglobulin class in serum First antibody class produced during an immune response
Agglutination Less efficient at agglutination of antigens Efficient at agglutinating microbes
Diagnostic Significance Used in diagnosing chronic infections, autoimmune diseases, and allergies Used as a marker for recent infections or initial response
Autoimmune Reactions Can contribute to autoimmune reactions Can contribute to autoimmune reactions
Rheumatoid Factor Can form immune complexes with rheumatoid factor Often detected in autoimmune disorders and infections
Similarities between IgG and IGM
Ø Both IgG and IgM antibodies are crucial components of the immune system and play roles in neutralizing pathogens, such as bacteria and viruses.
Ø Both IgG and IgM antibodies are produced by B cells in response to foreign invaders like pathogens.
Ø Both IgG and IgM antibodies have a Y-shaped structure composed of four protein chains, including two heavy chains and two light chains.
Ø IgG and IgM can contribute to immunological memory, meaning they provide protection against the same pathogen if encountered again in the future.
Ø Both antibodies can activate the complement system.
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