Secretion of chemokines by peripheral blood mononuclear cells (a) or CD14+ monocytes/macrophages (b) from four normal control subjects. 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 control subject. The horizontal bars represent the median values. The highest value for CXCL9 was off the scale and is shown numerically. None of the differences between groups was statistically significant.