The initial immune response to pathogens occurs through innate responses. Macrophages express pattern recognition receptors which distinguish pathogens from host tissue. They recognize microbial components called pathogen-associated molecular patterns. The innate immune system is more specific than previously thought. It shares certain features with the acquired immune response. These include: cytokines, chemokines, complement activation, phagocytic cells- macrophages and neutrophils, natural killer T cells and natural autoantibodies.
Ordinarily the initial innate response transitions into the acquired immune response which involves captured antigen presentation to lymphocytes leading to antibody production. The initial response releases IgM antibodies. A molecular switching causes the production of blocking IgG antibodies. For this process to occur continued immune stimulation via continued antigen presentation is required.
The Lyme bacteria are quickly put on notice shortly after infection due to the vigorous innate immune response. They quickly gear up to avoid immune destruction. Once they become intracellular or cystic, available antigens for presentation to lymphocytes become increasingly scarce. One can imagine that antibody producing antigens are present only long enough for the acquired immune response to initiate IgM production. At the time that IgG switching should occur, antigen loads may be so low that follow through IgG switching does not occur, or occurs very poorly.
If the germs lacked the ability to morph into antigenically invisible forms, as is the case with extracellular germs, then the full complement of IgG antibodies would be produced.
From time to time the spriochetes reappear from the hidden niches. The same process is repeated. There is an IgM response. The spirochetes in this adverse environment go back into hiding and the antibody producing machinery is shut down once again.
Hence, Lyme always looks like a "new infection" because of these atypical IgM only responses. These ideas may be useful as novel strategies for vaccine development are considered.