What is the Difference Between Toxoplasma IgG and IgM

The key difference between Toxoplasma IgG and IgM is that Toxoplasma IgG antibodies will replace IgM antibodies and will be present for the rest of the individual’s life while Toxoplasma IgM antibodies are produced after 1-2 weeks post-infection (toxoplasmosis).

Toxoplasmosis is an infection caused by a parasite named Toxoplasma gondii. It is an obligate intracellular parasitic protozoan. Humans are intermediate hosts. Infected definitive hosts are cats, and they shed infected oocytes via fecal matter. During the infection, the body produces IgM antibodies in measurable quantities after 1-2 weeks post-infection. After a few months, IgM antibodies become absent or present in undetectable quantities due to the appearance of IgG antibodies.

CONTENTS

1. Overview and Key Difference
2. What is Toxoplasma IgG 
3. What is Toxoplasma IgM
4. Similarities – Toxoplasma IgG and IgM
5. Toxoplasma IgG vs IgM in Tabular Form
6. Summary – Toxoplasma IgG vs IgM

What is Toxoplasma IgG (Immunoglobulin G)?

Toxoplasma IgG or immunoglobulin G is an antibody produced by the human immune system after a few months post-infection of toxoplasmosis by Toxoplasma gondii. This antibody is produced after a few months of infection, replacing the antibody IgM. IgG is an indicative measurement of previous exposure to toxoplasmosis. But it does not provide evidence of recent exposure. This means, once infected with toxoplasmosis, IgG antibodies will be present for the rest of the life. Therefore, a single positive Toxoplasma IgG is not a diagnosis indication of recent infection.

Figure 01: Toxoplasma gondii

IgG generally represents 75% of serum antibodies in humans and is the most common type of antibody that circulates in the blood. Plasma B cells synthesize and release IgG antibodies. During toxoplasmosis, the same plasma B cells synthesize IgG for the rest of their life. This is a protective step to fight against future infections. However, the presence of IgG in blood could be a false positive for a recent infection.

What is Toxoplasma IgM (Immunoglobulin M)?

Toxoplasma IgM or immunoglobulin M is an antibody produced by the human immune system after 1-2 weeks post-infection of toxoplasmosis by Toxoplasma gondii. This antibody is a significant clinical measurement of detecting toxoplasmosis. This is because Toxoplasma IgM is detectable in the blood after 1-2 weeks post-infection. Hence, it confirms the fact that an individual has been recently infected with toxoplasmosis. This indication is very important since it helps in providing therapeutics to pregnant women in order to cease the transmission of infection to the growing fetus.

Figure 02: Toxoplasmosis

Immunoglobulin M is the first antibody that gets synthesized against the fight of new infection by the immunity system of the human body. Similarly, during toxoplasmosis, the Toxoplasma gondii pathogen releases antigens which get detected by the immunity system to produce IgM antibodies. A positive Toxoplasma IgM result (≥3 IU/ml and index values of ≥0.800) indicates an acute toxoplasmosis infection. A single negative result does not rule out toxoplasmosis. The test should be repeated if the symptoms prevail and especially for patients at high risk for infection.

What are the Similarities Between Toxoplasma IgG and IgM?

  • IgG and IgM are immunoglobulins produced against the pathogen Toxoplasma gondii.
  • They are antibodies.
  • They indicate the exposure of toxoplasmosis.
  • Moreover, both antibodies are present in the blood.
  • Both antibodies are used for clinical evaluations of toxoplasmosis.

What is the Difference Between Toxoplasma IgG and IgM?

Toxoplasma IgG and IgM differ based on their presence following the infection. Toxoplasma IgG appears as a replacement of IgM at the later stage of the infection, while Toxoplasma IgM appears at the early stages of the infection. Thus, this is the key difference between Toxoplasma IgG and IgM. Detection of IgG is after a few months post-infection, and detection of IgM is after 1-2 weeks post-infection. So, this is another important difference between Toxoplasma IgG and IgM. Moreover, IgG results indicate previous exposure to toxoplasmosis, whereas IgM results are clinically significant since it indicates the recent exposure of toxoplasmosis.

The below infographic presents the differences between Toxoplasma IgG and IgM in tabular form for side by side comparison.

Summary – Toxoplasma IgG vs IgM

Toxoplasma IgG or immunoglobulin G is an antibody produced by the human immune system after a few months post-infection of toxoplasmosis by Toxoplasma gondii. It is produced after a few months of infection, replacing the antibody IgM. Toxoplasma IgM or immunoglobulin M is an antibody produced by the human immune system after 1-2 weeks post-infection of toxoplasmosis. This is the key difference between Toxoplasma IgG and IgM. Both IgG and IgM are immunoglobulins. Detection of IgG is after a few months post-infection, whilst detection of IgM is after 1-2 weeks post-infection. So, this summarizes the difference between Toxoplasma IgG and IgM.