Immune responses to Borrelia burgdorferi infection are now well characterized. Following infection there is an early T cell response and a more slowly evolving B cell response. IgM antibodies appear first and are followed by IgG and IgA. Early antibodies are primarily against a 41-kilodalton flagellum-associated antigen; responses to other spirochetal antigens develop later. Serologic assays that use whole B. burgdorferi preparations are not always able to detect an early rise in antibodies above a background of crossreactive antibodies present in most uninfected individuals. Moreover, some individuals with neurologic involvement who lack diagnostic levels of serum antibody to B. burgdorferi have high levels of the antibody in their cerebrospinal fluid. Specific T cell blastogenesis to B. burgdorferi can further document infection. Analysis of T cell subsets in
Lyme arthritis demonstrates a marked decrease in the CD4+2H4+ subpopulation in the synovial fluid, although normal numbers of these cells are present in peripheral blood. Immunologic measurements are useful in evaluating and treating a wide array of patients who may be infected with B. burgdorferi.