What does a high Lyme IgM antibody mean?

Here's what Dr. Joseph Jemsek has to say on the subject (on his website):

In virtually all infections, the IgM class of antibody (immunoglobulin) appears first and therefore represents a marker for an early infection. In most immune models, the IgM antibody gives way to the well-known IgG antibody class, usually regarded as the major enduring antibody response in chronic infectious diseases or other immune models. In almost all infection models, after just a few weeks, the IgM antibody level wanes to the point of being non-detectable and does not recur. However, a confounding fact in Bb infections is that the IgM antibody may persist for years, a very unusual situation in most disease states. Logically, one would have to conclude that this reflects an ongoing reactivation or persisting and continually renewing infectious state of Bb infection. Most active diagnostic laboratories involved with LD tend to agree with this notion. Therefore, the Jemsek Specialty Clinic acknowledges that a persistently positive IgM antibody response may qualify as laboratory confirmation for an active LD case.