Immunoglobulin (Ig) E may provide immunity against Borrelia burgdorferi infection (Lyme disease) in children which lasts throughout adulthood. We investigated the presence and persistence of IgE anti-B. burgdorferi antibodies (Abs) in paediatric patients infected with Lyme disease over time. Serum immunoglobulin levels, presence of IgG and IgE anti-B. burgdorferi components, and distributions of blood T, B and natural killer lymphocyte subsets were studied in B. burgdorferi-infected and -uninfected children (nephelometry, UniCAP Total IgE Fluoroenzymeimmunoassay, Western blot, flow cytometry). Total serum IgM, IgG, IgE and IgA levels, and distributions of blood lymphocytes (CD4(+), CD8(+), CD19(+)) of both groups, excluding CD8(+)CD60(+) T cells, were within normal ranges. However, infected, but not uninfected children made IgG anti-B. burgdorferi proteins p18, p31, p34, p41, p45, but not IgG anti-p60, and IgE anti-B. burgdorferi proteins p31, p34, p41, p45, p60, but not IgE anti-p18. These proteins were also detected in an infected child 1 year post-infection. Interestingly, CD8(+)CD60(+) T-cell numbers were significantly increased (fourfold) in infected, compared with uninfected, patients (P=0.001). These results demonstrate that specific IgE anti-B. burgdorferi Abs are generated and persist in children with Lyme disease and that CD8(+)CD60(+) T cells may play an important role in these responses.