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Immunoglobulins G and immunoglobulins M, also known as IgG and IgM, are antibodies that the body produces when it comes into contact with some type of invading microorganism. These antibodies are produced with the objective of promoting the elimination of bacteria, viruses, parasites and fungi, in addition to toxins produced by these microorganisms when they invade the body.
As they are important to assess the body's immune response to infection, the measurement of IgG and IgM can help in the diagnosis of various diseases. Thus, according to the test indicated by the doctor, it is possible to know whether or not these immunoglobulins are present circulating in the blood and, thus, whether the person has the infection or has had contact with the infectious agent.
What are IgG and IgM for?
IgG and IgM are proteins produced by the body in order to defend the body against infectious agents and their toxins. IgM is the first antibody to be produced when there is an infection, being considered a marker of the acute phase of the infection. This immunoglobulin is responsible for activating the complement system, which is a system formed by proteins, signaling that there is an infection and favoring the elimination of the invading infectious agent.
IgG is produced a little later, but still in the acute phase of infection, but it is produced according to the invading microorganism, being considered more specific, in addition to remaining circulating in the blood, protecting the person against possible future infections by the same microorganism. Understand how the immune system works.
IgG production is also induced by vaccination, in order to protect the body against a specific infectious agent. Thus, IgGs are a kind of memory that the organism creates for the rest of life.
Why is the exam done
The serological examination of IgG and IgM serves to detect the stage of several diseases, such as toxoplasmosis, rubella and infection by cytomegalovirus, for example. When a new infection occurs, the first antibodies produced are the IgM that decrease as the infection is controlled, giving rise to the IgG, which remains for the rest of life.
| Negative IgG | Positive IgG |
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Negative IgM | The person never came into contact with the microorganism. | The person came into contact with the microorganism in an old infection or was successful with the vaccine. |
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IgM positive | The person has or has been with an acute infection for a few days. | The person had a recent infection a few weeks or months ago. |
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Thus, the existence of large amounts of IgM for rubella, for example, is a sign that the infection is recent, and when its levels drop, those of IgG remain, which means that the infection is controlled and the body is producing specific antibodies against this virus, thus obtaining immune memory for that disease.
Thus, in a close contact with the virus, the risk of developing the disease would be minimal, since the person would have specific IgG antibodies against rubella that would act immediately. The same happens with vaccination, in which, in most cases, inactive viruses are administered that induce the formation of specific IgGs.
Examination of IgG and IgM in pregnancy
During pregnancy, the doctor may perform some blood tests to identify the infections that the woman has had and to assess her immune status, by measuring specific antibodies for each of the infectious agents.
There are 5 infections that, if they remain in pregnancy, may have a high risk of transmission to the fetus, being even more serious when the mother without antibodies to one of these viruses, acquires the disease during pregnancy, as is the case of toxoplasmosis, syphilis, rubella, herpes simplex and cytomegalovirus. See how cytomegalovirus can affect your baby and pregnancy.
Thus, it is very important to have a rubella vaccination about a month before pregnancy, and to have a serological test in order to treat other infections in advance.
Difference between IgG and IgM
Immunoglobulins G and M can be differentiated according to biochemical and molecular characteristics, with size, electrical charge and amount of carbohydrates in their constitution, which directly influences their function.
Immunoglobulins are structures similar to the letter "Y" and are formed by heavy chains and light chains. The termination of one of the light chains is always the same between immunoglobulins, being known as the light chain constant region, while the termination of the other light chains can vary between immunoglobulins, being known as the variable region.
In addition, there are regions of complementarity in both heavy and light chains, which correspond to the region where the antigen is able to bind.
Thus, based on the evaluation of the biochemical and molecular characteristics, it is possible to differentiate the types of immunoglobulins, including IgG and IgM, in which IgG corresponds to the highest circulating immunoglobulin in the plasma and IgM to the highest immunoglobulin present in the intravascular space, in addition to having their variable regions and extremities different patterns of complementarity, which has an impact on the function they perform.