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I am not that much educated in the medicine and immunology fields. So I noticed that there are tests for IgM and IgG immunoglobulins for various infections. I was not able to google quickly if IgM for one type of infection differs from the one for another type of infection.

I guess they differ because otherwise there would be only a few tests in the laboratory instead of dozens. But it would be great to hear some solid explanation.

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IgM (Immunoglobulin M) is the first antibody to appear in response to an antigen. It can be produced by the fetus and cannot be crossed by the placenta.

Typically one might test IgM to diagnose hereditary and acquired IgM immunodeficiencies or diagnose Waldenstrom macroglobulinemia. It can serve as the earliest Ig serologic diagnosis of infectious disease.

Lab tests for IgM may be increased in liver disease, chronic infection, hyper IgM syndrome, and secondary to nephritic syndrome; Waldenstrom macroglobulinemia, lymphoma, CLL, multiple myeloma (rare), Schnitzler syndrome, cold IgM antibody agglutin, and MGUS.

Lab tests for IgM may be decreased in protein-losing syndromes, non-IgM myeloma, and infancy/early childhood.

IgG (Immunoglobulin G) activates complement and fights infection. IgG represents 70-80% of the total serum immunoglobulins in normal adults. It exists in four subclasses (IgG1, IgG2, IgG3, and IgG4). IgG1 predominates as 65% of the total IgG. IgG of maternal origin provides passive immunity to the neonate. It is transported across the placenta.

Typically one might test IgG to diagnose IgG myeloma, diagnose hereditary and acquired IgG immunodeficiencies, and provide a serologic diagnosis of infectious diseases and immunity.

Lab tests for IgG may be increased in multiple myeloma, solitary plasmacytoma, MGUS, lymphoma, CLL, sarcoidosis, cirrhosis, autoimmune diseases, parasitic diseases, chronic infection, and intrauterine contraceptive diseases.

Lab tests for IgG may be decreased in protein-losing syndromes, pregnancy, non-IgG myeloma, Waldenstrom macroglobulinemia, primary immunodeficiency states, and agammaglobulinemia (if combined with other immunoglobulin decreases).

Sources: https://5minuteconsult.com/collectioncontent/2-152356/lab-tests/immunoglobulin-m-igm https://5minuteconsult.com/collectioncontent/2-152354/lab-tests/immunoglobulin-g-igg

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    $\begingroup$ Taylor, thank you for your answer that's all wonderful. But it actually does not address my question. I was asking why there is an IgM test for e.g. Borrelia burgdorferi and also the IgM test let's say for tick-borne encephalitis and they are priced differently. In other words I was asking how exactly the IgM for one infection differs from the IgM for another infection. $\endgroup$ – Alexander Arendar Oct 18 '17 at 16:55
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    $\begingroup$ IgM will be specific for certain epitope on the antigen. Basically, it will detect a "signature" of the various pathogens and be specific for it. Most of the IgM molecule will the be the same apart from a section called the hypervariable region. This hypervariable region will have different characteristics and specificity for each antigen that an organism has been challenged by. $\endgroup$ – Joseph Oct 18 '17 at 18:27
  • $\begingroup$ Joseph, thanks a lot. Could you put this comment as an answer and I will accept it. $\endgroup$ – Alexander Arendar Oct 18 '17 at 18:32
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The CDC currently recommends a two-step process when testing blood for evidence of antibodies against the Lyme disease bacteria. CDC

If Lyme Disease is suspected in at-risk patients, a sensitive serum serology screening test is performed to detect IgG and/or IgM antibodies to Borrelia Bugdorgeri. More specifically, an ELISA (Enzyme Linked Immunosorbent Assay) is a type of test that is used to detect IgM and IgG B. Burgdorgeri antibodies which is then followed by a Western blot test.

In tick-borne Encephalitis (TBE), laboratory diagnosis depends on the detection of specific IgM in either blood or CSF (Cerebral Spinal Fluid), which usually appears later, during the second phase of the disease. CDC

Pricing is dependent on the number of tests required to accurately diagnose one or both conditions, associated laboratory fees, your medical insurance coverage, etc.

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    $\begingroup$ You are very welcome Alexander. Glad I could provide some clarity. $\endgroup$ – Taylor Oct 18 '17 at 20:00
  • $\begingroup$ My mistake, sorry for that. $\endgroup$ – Chris Oct 19 '17 at 8:21

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