IgM and IgG: The message behind this

The signification of both immune system responses to various antigens has not stopped intriguing me. It started a few years ago when I had a patient presenting with all the symptoms of an acute bilharzia but with negatives tests results – urine and blood. I decided to treat him with praziquantel and to repeat the blood test for bilharzia 3 months later. The result came back showing high positivity in IgM.

I repeated this treatment very often afterwards and for various pathologies. I frequently observed an increase of IgG and the apparition – not necessarily constant – of the IgM.

My (inconclusive?) conclusion is:

• when pathogenic DNA enters the blood vessel, the IgM attempts to neutralise the germ;
• however, these intracellular germs take flight and enter the tissue;
• the IgM, being a bigger molecule, cannot follow the germ into the tissue;
• in response, the IgG, being a smaller molecule, are therefore able to take over the body’s defense within the tissue.

Thus, the IgM can only act as a defense in the circulating system.The presence of both IgM and IgG are both related to the original chronic infection, rather than the common perception that they relate to new and old infections, respectively. To compound the confusion, some patients can only produce one kind of the above-mentioned antibodies (IgM and IgG) regardless of the length of their disease.