Does a broad Borrelia burgdorferi IgG response indicate past exposure rather than active infection?

A broad Borrelia burgdorferi IgG pattern is most informative as evidence of prior immunologic exposure, not as a marker of whether infection is currently viable or clinically active.

Clinical interpretation

• Validated Lyme serology showing broad or multi-band IgG reactivity strongly supports prior B. burgdorferi exposure. In long-term follow-up of 79 individuals without active Lyme manifestations, two-tier IgG remained detectable 10–20 years after prior illness in 25% of those with earlier Lyme disease and 62% of those with prior Lyme arthritis.
• This persistence means that neither IgG positivity, antibody breadth, nor a high IgG level can distinguish remote, treated/resolved infection from active Lyme disease. Antibodies may remain detectable for years or decades after eradication.
• Active Lyme disease therefore requires correlation with a compatible current clinical syndrome, exposure context, and validated two-tier serologic testing. Serology is not a test of cure. Its sensitivity is lower in early disease (46.3%) than later stages, although specificity is high across control groups.

Mechanistic context

• Persistent IgG is compatible with an antigen-experienced humoral response and plausibly reflects established immune memory after prior exposure.
• However, circulating antibodies do not directly demonstrate durable, protective B. burgdorferi-specific memory B cells; long-lived antibody-secreting plasma cells can maintain serum IgG independently. Mouse studies also suggest that Borrelia infection may disrupt or delay germinal-center responses and functional memory formation, limiting inferences about the quality of cellular immune memory from IgG alone.

Bottom line

• A broad B. burgdorferi IgG response is strong evidence consistent with past exposure and plausible humoral immune memory, but it cannot independently determine whether infection is currently active.