Difference between herpes Igg antibodies and Igm

Question

Dr. Gallant: Could you explain to me what is the difference between IGG and IGM antibodies. I Know that when you get infected your body produces both kinds, but only the IGg remains present and the Igm desapears. Why is that? When do you test positive for IGM?, and how long do they last in your body? Months, days, years? The reason i asked is because I tested positive for cmv IGG antibodies, But negative for Igm. The levels of Igg antibodies where very high, does that mean that was a recent infection? Is there anyway to know how recent the infection was acquired? Thanks, and please answer.

Answer

In general, IgM antibodies indicate acute or recent infection. The appear early during the course of the infection and then disappear. IgG antibodies appear later and last longer, so they indicate past infection. In the case of CMV, most people have IgG antibodies because most people have been exposed to CMV. Since it's a herpesvirus that means that the CMV is still present in the body but is not causing disease.

If you're HIV infected, having a positive CMV IgG antibody means that you could develop CMV disease if your CD4 count were to fall below 50. The height of the antibody titer is not really very important. There is no way to know when you acquired CMV infection.