45 Differences Between IgG and IgM Antibodies

Introduction

IgG and IgM Antibodies : Immunoglobulins (Igs), or antibodies, are glycoproteins that are created in response to an immune response and have a unique affinity for the antigens that triggered the response.

The five main classes—IgG, IgM, IgA, IgD, and IgE—each of which has a wide range of subclasses. Each class’s distinctive traits and functions are a result of the H chains’ structural variations. The fact that there are two basic types of L chains—lambda and kappa chains—each of which can be coupled to any of the H chain classes, adds to the immunoglobulins’ already high degree of variability.

The most prevalent class of immunoglobulin is IgG. The blood and tissue fluids have the highest levels of it. Due to its basic four-chain immunoglobulin structure—two identical H chains and two identical L chains—each IgG molecule possesses two identical antigen-binding sites.

IgG is divided into four subclasses, each of which has unique biological characteristics despite only modest variations in its H chains. IgG provides some immune protection to the developing fetus since it is the only kind of immunoglobulin that can cross the placenta.

Additionally, these molecules are secreted into the mother’s milk, where they can enter the baby’s system and go to the circulation, where they provide immunity.

The antigen receptor on the surface of mature B cells, known as the IgM form, is the first class of immunoglobulin that is generated by mature B cells.

When IgM is secreted from the cells, five of the basic Y-shaped units are connected to create a large pentamer protein with 10 antigen-binding sites. The antigenic determinants present in bacterial outer membranes have a high affinity for this large antibody molecule. As a result of this IgM attachment, bacteria clump together or agglutinate.

Detailed Comparison IgG Antibodies vs IgM Antibodies

S.No.	Aspect	IgG Antibodies	IgM Antibodies
1	Class	Immunoglobulin G (IgG)	Immunoglobulin M (IgM)
2	Structure	Monomer	Pentamer
3	Heavy Chain Type	γ (Gamma)	μ (Mu)
4	Molecular Weight	Approximately 150 kDa	Approximately 970 kDa
5	Concentration	Most abundant antibody class in serum	Present in lower concentrations in serum
6	Maternal Transfer	Crosses the placenta	Does not cross the placenta
7	Neonatal Immunity	Provides passive immunity to fetus/newborn	Initial production during neonatal immune response
8	Half-life	Longer half-life (about 21 days)	Shorter half-life (about 5 days)
9	Presence in Early Infections	Generally appears later in infections	Often the first antibody class produced in response
10	Complement Activation	Efficiently activates classical complement pathway	Less efficient in activating complement
11	Opsonization	Effective opsonization for phagocytosis	Less effective opsonization
12	Antigen Receptors	Binds to Fcγ receptors on immune cells	Binds to different Fc receptors on immune cells
13	Allergic Reactions	Can mediate allergic reactions	Not as commonly associated with allergies
14	Fetal Protection	Provides long-term protection to the fetus	Provides initial defense during early infections
15	Immunization	Often indicates past exposure or vaccination	Can indicate recent/current infection or primary immune response
16	Memory Response	Plays a key role in immunological memory	Initial response in primary immune response
17	Maturation	Developed later in the immune response	Developed earlier in the immune response
18	Secondary Response	Higher concentration in secondary immune response	Often less prominent in secondary immune response
19	Disease Associations	Often associated with chronic infections	Early marker of acute infections or recent exposure
20	Tissue Distribution	Widely distributed in tissues and fluids	Present mainly in blood and lymph
21	Transplacental Transfer	Transferred from mother to fetus	Not transferred across the placenta
22	Role in Autoimmunity	Can contribute to autoimmunity	Generally not as involved in autoimmunity
23	Hemolytic Disease of Newborn	May cause hemolytic disease in Rh-incompatible pregnancies	Not as commonly involved in this condition
24	Blood-Brain Barrier	Can cross the blood-brain barrier	Generally does not cross the blood-brain barrier
25	Immune Complexes	Forms immune complexes with antigens	Less commonly forms immune complexes
26	Primary vs Secondary Immune Response	Often more prominent in secondary immune response	Often more prominent in primary immune response
27	Secretion	Present in mucosal secretions	Not present in mucosal secretions
28	Rheumatoid Arthritis	Can contribute to the pathogenesis of RA	Generally not a major factor in RA
29	Half-life in Newborns	Short half-life in newborns	Relatively longer half-life in newborns
30	Role in Transplantation	Can be involved in allograft rejection	Not as strongly implicated in transplant rejection
31	Diagnostic Use	Often used in serological tests	Used in diagnostics, particularly for acute infections
32	Bacterial Infections	Involved in immunity to bacterial infections	Initial response to bacterial infections
33	Viral Infections	Plays a role in defense against viral infections	Often involved in early viral defense
34	Rheumatoid Factor	IgG can be targeted by rheumatoid factor	Not as commonly targeted by rheumatoid factor
35	Transplantation	Can be involved in organ transplant rejection	Less commonly implicated in transplant rejection
36	Evolutionary Age	Evolved later in vertebrate immune system	More evolutionarily ancient antibody class
37	Viral Neutralization	Can effectively neutralize viruses	Less effective in viral neutralization
38	Role in Immune Complex Diseases	Implicated in immune complex diseases	Less commonly involved in immune complex diseases
39	Cancer Immunotherapy	Target for some cancer immunotherapies	Not as frequently targeted for immunotherapy
40	Potential Tissue Damage	IgG-mediated immune responses can lead to tissue damage	Not as prone to causing tissue damage
41	Placental Barrier	Can cross the placental barrier	Does not cross the placental barrier
42	B-Cell Receptor	Binds to antigens via B-cell receptor	Binds to antigens via B-cell receptor
43	Arthritis	Can contribute to inflammatory arthritis	Not typically associated with arthritis
44	Antigen-Antibody Complexes	Commonly forms antigen-antibody complexes	Forms antigen-antibody complexes less frequently
45	Abbreviation	IgG	IgM

Frequently Asked Questions (FAQs)

1) Antibodies are made by lymphocytes. Is it real?

B- and T-cells are the two main subtypes of lymphocytes. T-cells kill the body’s own cells that have contracted viruses or developed into cancer, whilst B-cells generate antibodies to attach the pathogen. So, yes, lymphocytes do really generate antibodies.

2) What Are Low Immunoglobulin Levels Indicative Of?

Low immunoglobulin levels indicate that the immune system isn’t functioning as effectively as it should.

Steroids and other immune system-weakening medications may be to blame. problems with diabetes, the state of having damaged or failing kidneys is known as renal disease or kidney failure.

3) Which antigen can pass through the placenta?

The only antibody that passes through the placenta is IgG because of the following reasons.

passive immunization that offers babies protection.
Bacterial toxins are neutralized by it.
It speeds up the phagocytosis process.
provides the growing fetus with immunity.

4) After acquiring the mother's antibodies through the placenta, the fetus receives an immunization. This particular vaccination is known as?

Antibody-mediated immunity passed on to a fetus or child by its mother is known as maternal passive immunity, which is a type of naturally acquired passive immunity.

Passive immunity, on the other hand, is acquired protection against infection by the transfer of antibodies to a vulnerable individual. Passive immunity is distinguished from active immunity by the immune system’s response to a pathogen or a vaccine.

Therefore, a newborn’s immunity from the mother’s milk is passive immunity that the body naturally acquired over time.

5) How many IgM molecules include antigen-binding sites?

When IgM is secreted from the cells, five of the basic Y-shaped units are connected to create a large pentamer protein with 10 antigen-binding sites. Particularly adept in attaching to antigenic determinants present on bacterial outer membranes is this large antibody molecule.