The expression of the chemokine receptors CXCR3 and CCR5 on unstimulated or Borrelia burgdorferi - or interferon-gamma (IFN-γ)-stimulated peripheral blood mononuclear cells (PBMCs) or synovial fluid mononuclear cells (SFMCs) from six patients with Lyme arthritis. (a) The flow cytometry data are shown for the PBMCs of one patient. After 5 days of incubation, nonadherent cells were resuspended, collected, and stained with antibodies. A forward scatter/side scatter (FSC/SSC) gate (R1) was used to exclude dead cells, and a CD3/CD4 gate (R2) was used to further restrict analysis to T cells. The number of events in each gate per number of events collected or the percentage of gated cells positive for CXCR3 or CCR5 is indicated on the histograms. (b) The percentages of T cells that were brighter than the isotype control are shown. The horizontal bars represent the median values. Significant differences between PBMCs and SFMCs are shown in brackets.