Question about mycoplasma IgG level I have been treated with antibiotics for the mycoplasma M. Pneumoniae for the last two years. My IgG is higher now than when I started treatment. My original test showed very high IgG although the IgM was in the normal range. My CFS doctor feels a high IgG is significant but my Lyme doctor does not. Do you feel a high mycoplasma IgG needs to be treated? Reply: Since M. pneumoniae is an intracellular infection, meaning that it hides inside cells where it cannot stimulate much of an immune response. When an immune response is detected, especially in high titers, it usually means that the infection is active and some microorganism is being released from cells. Borrelia is more often found in blood than Mycoplasma, possibly because it is more often released from cells, and its antigens are apparently more immunogenic and produce a stronger immune response, so it is easier to detect.