Secretion of chemokines by peripheral blood mononuclear cells (a) or CD14+ monocytes/macrophages (b) from 24 patients with Lyme arthritis. Cells were not stimulated, or they were stimulated with Borrelia burgdorferi or interferon-gamma (IFN-γ) or both. After 5 days of incubation, the levels of chemokines were measured in the culture supernatants. Each point represents the value of an individual patient. The horizontal bars represent the median values. The highest values for CXCL9 were off the scale and are shown numerically. All significant differences among stimulated and unstimulated cells are shown in brackets and had a P value of less than 0.001.